Neuroscientist Reveals The LIFESTYLE HABITS That Prevent COGNITIVE DECLINE! | Dr Tommy Wood

Dr. Rangan Chatterjee 0:00 I think that the common view in society is that as we get older, our brain function has to decline. What's your view?

Dr. Tommy Wood 0:13 I think that it's true that it does on average, and you can see that, uh, multiple s- uh, large population studies show that pretty much every cognitive function that you can measure decreases fairly linearly over time, except for, um, memory about the good old days. Every, um... The majority of people seem to be able to remember the good old days, but every other, you know, the executive function, short-term memory, all these other functions decline over time. However, I don't think it needs to be that way. Um, part of what I find to be very interesting about, uh, cognitive function and the way we think about it when we age, is that there's this story that says you're born with so- like, X number of brain cells, and then, like, every time you maybe drink a little bit too much or you don't sleep, you're killing brain cells, and it's just this inexorable decline that you can't change, and that's not true. Um, we can make new brain cells in some areas of the brain, um, particularly in, uh, some areas of the hippocampus, which is associated with memory. Um, but even then, even if you're not making new cells, the cells you have can make new connections. You can change the structure around those cells in the brain, which is what helps support their function, and you can see that in multiple studies. Even as people get older, you give them a new challenge of some kind, you challenge their brain, and then they'll make new connections. Those area of the brains will get bigger. You can see it on an MRI scan. So what I find interesting is that just like the muscles of your body, which is easier to think about 'cause you can visi- visibly see it, if you train it-

Dr. Rangan Chatterjee 1:52 Yeah

Dr. Tommy Wood 1:52 ... it gets bigger. You can see strength much more easily. But the brain is, is very similar. If you challenge it and you ask it to do new things, it can adapt, um, pretty much any time i- in life. So part of it is getting over this thought that, um, you know, "I'm old. My brain doesn't work anymore. There's nothing I can do about it." So stop telling ourself that story, and then introducing things to, to ask more of your brain, and then it will function better.

Dr. Rangan Chatterjee 2:18 That's really empowering for us to realize that there are actually things that we can do. We're definitely gonna get super practical and talk about a lot of those things. You mentioned that there are studies showing that various functions of cognition, various functions of our brain do start to go down with age. These studies that have been done, when have they been done? Because we know that there's a poor level of background health in the population.

Dr. Tommy Wood 2:50 Yeah.

Dr. Rangan Chatterjee 2:50 Metabolic health, you know, cognitive health, all kinds of things that generally society is pretty unhealthy now in many ways, so therefore, are we just studying a sick society and seeing cognitive decline go down? Or is it something that's actually an inevitable part of aging, in your view?

Dr. Tommy Wood 3:09 So until we get to the point where we can completely stop the aging process, which I think is unlikely to happen any time soon, function will decline over time in anybody. When you ... Like, how long that takes and what the sort of the, the ultimate end of that, I think, is modifiable, and very much so. So there is gonna be a decline over time, but you can change the trajectory quite dramatically, so that, that's way where you end up. Um, but when you ask about how these studies are done, th- this... I mean, I guess there's two different ways. One is you do this large population observational study, so you, you look at the cognitive function in multiple people of different ages, and then you kind of see that across ages as you look at older people, their cognitive function declines. Uh, you can do that in large populations. Uh, in a smaller population, you might be able to take the same people and look at their cognitive function over time.

Dr. Rangan Chatterjee 4:05 Mm.

Dr. Tommy Wood 4:06 Um, and, or look at their, you know, future risk of dementia, and that's, and that's been done, too. Um, however, when you're studying the population, and in general, these are studies done in m- modern, Westernized, industrialized, uh, populations, and we're at a stage where we have to say that those populations are, on average, unhealthy. Um, they... The vast majority have at least one of the components of metabolic syndrome. They, on average, take one prescription medication. On average, have at least one chronic health condition. So we know those various things, that poor systemic health is associated with worse brain health and an increased risk of cognitive decline. So you're right. It's very difficult to study very healthy people and look at what happens to their brains, 'cause there just aren't very many of those people to study anymore.

Dr. Rangan Chatterjee 5:00 When we think about cognitive function, a lot of people are thinking about Alzheimer's.

Dr. Tommy Wood 5:06 Yeah.

Dr. Rangan Chatterjee 5:06 They're thinking about, "I don't wanna get Alzheimer's when I get older." Maybe they've got a parent or, you know, an auntie or a grandparent. You know, it, it is affecting many people's lives these days. They're seeing what happens. So I wonder if you could explain, first of all, what is Alzheimer's? Um, and just, just compare that to cognitive function, because declining cognitive function, so declining brain function as we get older, is not necessarily the same as Alzheimer's, is it?

Dr. Tommy Wood 5:40 What we call Alzheimer's disease is essentially two different diseases, in my mind. The original Alzheimer's disease, as described by Dr. Alois Alzheimer, is what we would now call early onset or familial Alzheimer's disease, is caused by a single mutation in a single gene. There are a few genes that, that you could have a mutation in, but you just need a, a mutation in one gene that causes early ... dementia, like 30s or 50s. So third to fifth decade of life, and has sort of like a steady decline and quite rapid

Dr. Rangan Chatterjee 6:13 And that's a huge genetic component

Dr. Tommy Wood 6:15 It's almost all genetic

Dr. Rangan Chatterjee 6:16 Okay

Dr. Tommy Wood 6:17 And it's less than 5% of cases of Alzheimer's disease. So it's, it's, it, it's fairly rare, uh, relatively. What most people think about when they think about Alzheimer's disease is what we might call sporadic or late-onset Alzheimer's disease. It maybe occurs in your 60s to 80s, or later if you live longer, and it's very heterogeneous. It's very variable from person to person. Um, there's, uh, this old adage that says that, "If you've seen one person with Alzheimer's, you've seen one person with Alzheimer's," 'cause it's like how it expresses itself in different people is very different based on-

Dr. Rangan Chatterjee 6:52 Yeah

Dr. Tommy Wood 6:52 ... their environment, their genetics, their lifestyle, their general health. And that second disease, I, I don't think is Alzheimer's disease as he originally described it. They're very different, and you can, you can look at them completely separately. So that, we might call, or I have called in, in a paper that I've published with a colleague of mine recently, age-related dementia. Um, and it's influenced by all the things that we just mentioned, and we could talk about that more. As you go into that, there is this period of cognitive decline. So, uh, clinically you might call it mild cognitive impairment as, as a specific diagnosis, and again, it's sort of like the prodromal period before frank, uh, dementia sets in. But everything happens on a continuum. So if you look at cognitive function over the li- over the lifespan, like I said, it, it sort of from your 20s or 30s it, on average, steadily decreases. Um, so these processes are happening, are starting much earlier in life, and that's, that's been described. These processes of the, um, maybe the, uh, so the brain atrophying, you know, starting to lose cells, uh, but also measurable changes in function. Some of these things you can see on scans. It might start very early, but it takes a long per- it takes a long time before you get to the point where your actual function is detectably decreased, if that makes sense.

Dr. Rangan Chatterjee 8:10 Yeah

Dr. Tommy Wood 8:11 And the, the way I, I again liken it to, uh, physical function or, and because, uh, 'cause again I think that's something that people can picture more easily. So if you imagine that whatever you're able to lift, say, um, on a daily basis, um, you know, shopping bags, things like that, you can probably lift more than that, right? You have this headroom, what you have to do every day versus what you would be capable of doing. However, as function declines, eventually your maximum capacity is what you're able to do every day, and that's what we would call frailty, physical frailty. Because you have no capacity for... So say if you stumble, you can't save yourself, right? You're gonna fall over. Um, or if we're thinking about leg strength, your leg strength will decline to a point where getting up from a chair is as much as you can do, right? You have no headroom. And so that's what happens with cognitive frailty or cognitive decline. You just don't have any extra capacity. Uh, you know, there's, the brain can't do any more than you're asking of it every day. And eventually the, you get to the point where the function isn't good enough to do your, your daily tasks, and then that's when you start to, to go down into dementia.

Dr. Rangan Chatterjee 9:22 Yeah. Super helpful and, and really, really clear. So as we progress this conversation, let's be really clear that when we're talking about, you know, Alzheimer's, we're not talking about the early onset-

Dr. Tommy Wood 9:37 Yeah

Dr. Rangan Chatterjee 9:37 ... the classic Alzheimer's. We're mostly gonna be talking about age-related dementia. This, I think, is what many people are quite scared about.

Dr. Tommy Wood 9:48 Yeah

Dr. Rangan Chatterjee 9:49 Uh, certainly the older people get, and it's not uncommon now in people's 30s or 40s to go, "Man, I can't remember stuff like I used to," right? So I think everyone is aware of the kind of phenomena we're talking about. Let's say people get a diagnosis in their 60s. When does it actually start in their brain?

Dr. Tommy Wood 10:12 So it probably start, it probably starts right after your brain finishes developing. So after you've built, you've built the brain, you've built the connections, you've put down the final parts of white matter in your prefrontal cortex that maybe happened in your 20s or, you know, mid-20s, early 30s, that's, that's when the decline starts. So you, you increase, uh, you build the brain, you increase its function, and then it starts to decline. I don't mean that in a negative way. That is just when the process starts. And part of that, I think, is driven by societal pressures, um, rather than some process that we have no control over.

Dr. Rangan Chatterjee 10:51 Yeah

Dr. Tommy Wood 10:52 And what I mean by that is, um, I ... To try and think about what a brain needs to maintain its function, because I'm a, I'm a neonatal neuroscientist. That's my, my day job. So I think about what does it take to build a brain in the first place? And obviously you need, you know, the actual structure, so you need the nutrients and the, the fats and the things that, that, that make up your brain. But you also need the kind of stimulus that it takes to build, build connections. And so think about babies and toddlers. They're continuously exploring, trying new things, failing, um, uh-

Dr. Rangan Chatterjee 11:30 [laughs]

Dr. Tommy Wood 11:30 ... build- like, building motor skills, right? Tripping over, trying to stand, trying to climb trees. Uh, but they do the same with language. They do the same with social skills. They're constantly pushing themselves, trying new things, and sometimes they fail. Um, but you know, they laugh it off and they just keep going. And then they do that for a period of time, and then they, they sleep. They rest and recover. They need that for what we call consolidation in the brain, uh, for that period of plasticity where you're sort of building new connections. Adults don't do that.

Dr. Rangan Chatterjee 11:58 Yeah

Dr. Tommy Wood 11:59 We do the same things again and again and again. And part of what I think happens, um- ... in your 20s and 30s is that you leave formal education, you leave that period of trying new things, learn new things, you know, learning how to drive, all of that's done. And then you become increasingly good at the things that you do every day, which isn't stimulating your brain in the same way.

Dr. Rangan Chatterjee 12:25 Yeah.

Dr. Tommy Wood 12:25 So I think we can build those things back in, but part of the reason why that decline happens at that period of time is because that's the time when you stop challenging your brain to develop new connections and to, to, to maintain the structure that it has.

Dr. Rangan Chatterjee 12:39 Yeah, I mean, it's so, so beautifully simple the way you look at that when you look at kids.

Dr. Tommy Wood 12:45 Yeah.

Dr. Rangan Chatterjee 12:45 Try new things, they're failing, they're exploring, they're experimenting, and then they sleep.

Dr. Tommy Wood 12:50 Yeah.

Dr. Rangan Chatterjee 12:51 Right? So you're giving it the stimulus, you're giving it that new information so the brain adapts, and then you're resting so it can grow stronger.

Dr. Tommy Wood 12:58 Yeah.

Dr. Rangan Chatterjee 12:59 And yeah, a- as adults, certainly as adults in the current society in which we live, um, we don't tend to do that. It's really interesting, Tommy, as you were talking and you were saying that that cognitive decline, that, that decline in brain function probably starts somewhere around our early 30s, and before you were talking about how our brain mirrors our muscle.

Dr. Tommy Wood 13:22 Mm-hmm.

Dr. Rangan Chatterjee 13:23 Well, we know that from the age of 30 we start to lose lean muscle mass-

Dr. Tommy Wood 13:28 Yeah

Dr. Rangan Chatterjee 13:28 ... unless we do something about it. So there really is a very strong similarity, isn't there, between muscles and brain?

Dr. Tommy Wood 13:35 The more I think about this and look at this from the societal down to the biochemical level, I think they mirror one another almost exactly. And I... It's the same with almost any tissue in the body. Um, in particular the thing about muscle tissue and the brain, it's very easy to, to draw lines across them, which is that the structure and function of a tissue is directly proportional to the demands you put on it, right? The more you challenge your muscle, the more muscle you grow. But in order to grow, you need a period of rest and recovery. And the brain is exactly the same. Um, and you can think about that in terms of building new connections, building new cells, um, but also processes of repair. So, uh, autophagy is this thing that people are really interested in now, where you start to break down the accumulation of damaged proteins and other things within cells. And in, in muscle tissue, the best thing to do if you want to increase autophagy in muscle tissue is you exercise it, you move it. Um, and it seems that the brain is the same, that stimulating the brain is protective because it upregulates these, uh, repair processes. And so that then gives you this framework where you say, "Well, in order to improve the function and structure of my brain, I need to challenge it, but then I also need to give it everything that it needs in order to adapt to that challenge." So that can be nutrients, it can be sleep and recovery, it can be making sure that there aren't toxins in your environment. Like we know air pollution is linked to an increased risk of dementia, things like that, which then may inhibit your abili- ability to, to adapt. Uh, but the primary driver in my mind really seems to be, like, how much are we asking of our brains, and then how much are we allowing it to recover? Um, and that, that brings in a part of things around health equity because not everybody gets to ta- you know, gets to sleep. Um-

Dr. Rangan Chatterjee 15:22 Yeah

Dr. Tommy Wood 15:22 ... you know, people working multiple jobs with, um, you know, or lots of family members in a, in a small space, it's very difficult to sleep. Or being chronically exposed to societal stresses, and that chronic stress is probably something that pre- prevents adaptation because you don't get a recovery period. So you can start to see how all the things that we know are linked to an increased risk of dementia, um, may be linked to, first of all, how much are we challenging our brains, and then how are we supporting it in its ability to then adapt to that challenge?

Dr. Rangan Chatterjee 15:55 I wanna get to the practical things we can do shortly. Earlier today I spoke to Tim Peake.

Dr. Tommy Wood 16:03 Mm-hmm.

Dr. Rangan Chatterjee 16:06 Um, British astronaut. He spent six months on the International Space Station, and there's a couple things in that conversation that I think really speak to what you have been speaking about. He spoke about the training process. He had six years of training. Now, in that training there's all kinds of things they do. They put them in super uncomfortable situations. They're really trying to build physical resilience, psychological resilience. They take them to cold, dark caves. They deprive them of time. They... You can see what happens when you are under that much pressure. So they're, they're being pushed out of their comfort zone to see how they respond. But he also had to learn Russian. Now, I don't know how old Tim was, but that's interesting based on what you have said, right? 'Cause I'm thinking, [lips smack] yes, he's being trained to be an astronaut, so, you know, teamwork, be resilient, deal with pressure. But actually a lot of that training is also gonna reduce the likelihood that he's gonna get age-related dementia. W- what, what would you say to that?

Dr. Tommy Wood 17:20 Um, I'm sure that's the case. Um, other than the fact that, uh, microgravity or lack of gravity has-

Dr. Rangan Chatterjee 17:26 [laughs] I was thinking that as I said the question

Dr. Tommy Wood 17:28 ... has-

Dr. Rangan Chatterjee 17:28 Otherwise [laughs]

Dr. Tommy Wood 17:29 ... has an interesting effect, at least on muscle tissue. Um, and so how it affects the brain would be an interesting thing. But in general, from his time on Earth, yes, all of those things are-

Dr. Rangan Chatterjee 17:39 Had, had he done the training and not gone to space-

Dr. Tommy Wood 17:41 [laughs] Yeah

Dr. Rangan Chatterjee 17:41 ... then that would be excellent-

Dr. Tommy Wood 17:42 That'd be perfect

Dr. Rangan Chatterjee 17:42 ... brain training.

Dr. Tommy Wood 17:43 Yeah.

Dr. Rangan Chatterjee 17:44 But again, learning Russian, like, we tend to learn languages at school because we have to.

Dr. Tommy Wood 17:49 Yeah.

Dr. Rangan Chatterjee 17:49 But that, that new paper you published, which was wonderful, like it is such-

Dr. Tommy Wood 17:54 Thanks

Dr. Rangan Chatterjee 17:54 ... a good paper, and we'll, we'll definitely link to it in the show notes so people can read it themselves. You made a very strong case with your, I think, co-authors?

Dr. Tommy Wood 18:02 Yeah.

Dr. Rangan Chatterjee 18:03 Um, that a lack of stimulus to our brain May well be causative, so not associated with, but causative of this age-related decline in brain function

Dr. Tommy Wood 18:17 So that's certainly how I read the literature. And so I, I published this paper with, uh, uh, Dr. Josh Turknett, who's a, who's a neurologist, and it's difficult to really unpick causation in humans to, to say you've really proven it. And in fact, it's impossible to prove anything in biology. I think that, you know, people need to appreciate that. However, if you look across, you know, a broad range of animal studies, human studies, that's really again, how it looks and it comes down to how much you're challenging your brain and then supporting your ability to adapt to it. So it's not the only thing, but again, uh, to draw, uh, a connection back to, to muscle tissue, imagine you had the perfect diet and plenty of sleep and strong social connections, all these things that we know are supportive of health, um, but you didn't do any exercise. You were, you know, you were res- you were sort of confined to your bed, and there's been hundreds of studies

Dr. Tommy Wood 19:19 done on bedrest or, uh, immobilizing a limb. You know, if you've broken your ankle and then you put your leg in a cast, when you take that cast off, the muscles on that leg have gotten smaller. I know if you lay in a bed and you don't move, your muscles get smaller. So even if everything else is perfect, if you don't stimulate that tissue, it will reduce in both size and function. And the brain seems to be, uh, seems to be the same. I think one of the most interesting lines of evidence that supports that idea is based around retirement. Uh, there are multiple studies in multiple populations that suggest that the earlier you retire, the earlier you get cognitive decline and dementia. And this is particularly in people who have cognitively stimulating jobs. Um, in fact, the, then the effect is bigger there.

Dr. Rangan Chatterjee 20:06 Mm-hmm.

Dr. Tommy Wood 20:06 And this is after you adjust for... You know, you might retire early 'cause you have a medical condition that's also associated with, with cognitive decline. This is after you adjust for those things. You see this sort of rapid decline in cognitive function when people retire. Um, and that's because work is, uh, the thing that's most cogn- cognitively stimulating for most people. And then you remove that, and you don't replace it with other stimulus, that's when you start to see the sort of inexorable or sort of faster decline, uh, in cognitive function.

Dr. Rangan Chatterjee 20:32 So for people listening, right, Tommy, who either have retired themselves or are thinking about their parents, or we have a lot of younger listeners these days who might be thinking about their grandparents. Based upon that, they've retired, they've left their job. So what practical advice would you give to them as to how they can sort of make up for that lack of cognitive stimulus?

Dr. Tommy Wood 20:57 So what's nice about this is that it seems that there are many different ways to overcome this, all of which are very likely to be effective. So you alluded to one of them, which is learning a language, and learning languages even late in life, have been shown to im- improve cognitive function and be protective for certain, uh, areas of the brain. Uh, physical movement does it. Uh, resistance, there are randomized controlled trials that show that resistance training, uh, improves the structure and function of certain areas of the brain. So just going and starting to lift something if you've never done that before. Um, with respect to movement, it seems that you get more benefit if you do a movement that has some kind of coordination component. So you might think Tai Chi or yoga. Uh, one of the modalities that's best, um, researched is dancing. So if you have older, o- older adults in their 60s and 70s and you make them do some kind of circuit training at the gym, or the same amount of effort of activity but in a dance class instead, they'll get more cognitive benefit from the dancing. And actually you can even see that on an MRI scan. Their hippocampus, uh, gets, gets bigger more than the other group. And what's nice about something like dancing is that there's a music component, there's a social component, there's a movement component. All of these things we know support health, both, you know, physically and mentally.

Dr. Rangan Chatterjee 22:17 So all of those things I understand in isolation would be helpful, music, social connectivity, very, very good for the brain, physical movement. All these things individually I think have benefits. But you chuck all three together and mix them up at the same time, then you're... You know, it's almost like a, like a three-dimensional stimulus for the brain rather than just a, a one-dimensional one.

Dr. Tommy Wood 22:41 Yeah, exactly. And there is some specificity in terms of what are you asking your brain to do versus what does it get better at? So when they've done studies of individuals that did a very challenging learning stimulus, um, the best example that I know of is taxi drivers who are learning the knowledge, um, in London. So, so they, they took three groups, or they, they ended up with three groups of individuals. So for those who don't know, I guess people don't need to learn the knowledge anymore, but it's, uh, 25,000 streets, a six, uh, six, uh, mile radius around Charing Cross station in London. You have to learn to be a taxi driver in London. So it's a huge amount of things you have to like... I mean, just the memory component is, is, is incredible. And it took two years. Uh, so people who they... And they did brain scans before and after, and those who learned the knowledge and passed, they saw an increase in the size and some of, some measures of intensity of connection of the hippocampus, which is the area related to memory in the brain. And these are, these are adults in their 30s and 40s. Those who, um, didn't manage to pass didn't see that, and then also they had a control group that, that, where they didn't see any change. So it was specifically in those people who managed to do this huge learning task saw benefits in that area of the brain. But then they saw a slight decrease in some other aspects of cognitive function because they put so much into memory. So if you, if you really focus on one thing, you become really good at it, but then maybe you've taken away some, some things from other areas of the brain. It's possible. So if you take something that gives you all of those at the same time, so you mentioned like the social connection, uh, the, the benefits of physical activity, plus the coordination component, uh, plus music, I think There's multiple aspects of stimulus, there's multiple parts of the brain, but they seem to come together in a way that's... It's difficult to say if it's true synergy, which is that it's more than the sum of its parts, but definitely seems to be more beneficial than doing any of those things individually.

Dr. Rangan Chatterjee 24:39 Just on the black cab London, uh, taxi example, which I think is a really beautiful one to think about.

Dr. Tommy Wood 24:45 Uh-huh.

Dr. Rangan Chatterjee 24:46 Uh, certainly my experience if I'm ever in London is if you take an Uber and they're just following the sat nav.

Dr. Tommy Wood 24:53 Uh-huh.

Dr. Rangan Chatterjee 24:53 You go the black cab driver, they seem to go through all these crazy back roads, and you get there quicker.

Dr. Tommy Wood 24:59 Mm.

Dr. Rangan Chatterjee 24:59 So I suspect there's still something going on [laughs] with that test there. But the wider point for me is, you know, we're talking about how society changes our behaviors, smartphones, GPSs-

Dr. Tommy Wood 25:13 Mm-hmm

Dr. Rangan Chatterjee 25:13 ... and our cars, right? So many people now have no real perception of where they're going if that sat nav is not on.

Dr. Tommy Wood 25:22 Mm-hmm.

Dr. Rangan Chatterjee 25:24 So what do you think the consequences might be as we outsource more and more of our brain function to devices and technology?

Dr. Tommy Wood 25:39 I think as the way that you describe it, there's, there's clearly a possibility that it's gonna be detrimental, right? We've offloaded all the things that our brain is really good at that ma- you know, some of which make us u- uniquely human, and we've offloaded them, and we no longer ask our brains to do those things. And if you don't ask a tissue to have a certain function, it will no longer have that function, right? It's the same with, um, you know, your cardiovascular function if you're running. Um, so, so I think that's definitely something we need to consider. But there's also the possibility that with the a- with the sort of advent of new technology, we ask our brains to do different things and be good at different things.

Dr. Rangan Chatterjee 26:23 Yeah.

Dr. Tommy Wood 26:23 And that may also be just as good, right? So I notice myself, 'cause I, I mean, I have access to huge volumes of information, and for my job, I need to know huge volumes of information. And the majority of the time, I probably don't remember all of the things that I could possibly need to remember.

Dr. Rangan Chatterjee 26:40 Mm-hmm.

Dr. Tommy Wood 26:41 And I notice that what I remember instead is where that information is, right? So I still have memory of important things, but I don't necessarily remember the exact fact, but I know where that fact is. So when I'm preparing to do a podcast, I'm like, I, I know I need this piece of information from this paper, and I know who wrote it, um, and I know where to find it so I can go back and read it.

Dr. Rangan Chatterjee 27:03 Mm-hmm.

Dr. Tommy Wood 27:03 So I'm still requiring memory, but just in a different way, um, which I think is, is probably not necessarily detrimental. It's just different.

Dr. Rangan Chatterjee 27:10 Yeah. And I, and I guess, you know, thinking about what you said just before that, that if you are putting all your attention on learning the huge amount of roads and back roads around Charing Cross station, that takes up so much of your cognitive reserve that you have less available for other stuff.

Dr. Tommy Wood 27:34 Yeah.

Dr. Rangan Chatterjee 27:35 So yeah, sure, you're a great taxi driver, but maybe other areas of your brain have been neglected. I guess you could make the case with technology that, I don't know, let's say you're driving to a podcast to be a guest.

Dr. Tommy Wood 27:48 Mm-hmm.

Dr. Rangan Chatterjee 27:49 Instead of using up your cognitive reserve on the way, trying to figure out, where am I going, where's a street? Actually, it can make it quite a stress-free experience if it's all working and, and, you know, things go smoothly.

Dr. Tommy Wood 28:03 Yeah.

Dr. Rangan Chatterjee 28:03 Which means that you have more cognitive reserve for the important activity that you're about to do.

Dr. Tommy Wood 28:09 Yeah. I, I think so. Um, there is, you know, more and more evidence that suggests that, you know, you can't... You don't burn more calories by thinking harder. Um, but it doesn't require m- your brain doesn't require more or less total energy. But it, there certainly seems to be reserves of things like, you know, willpower and decision-making and, you know, access to cognitively challenging things that you can probably only do for a short period of time before you need some rest and recovery. So if you're offloading difficult but more menial tasks to something else, that does give you greater-

Dr. Rangan Chatterjee 28:45 Yeah

Dr. Tommy Wood 28:45 ... capacity in theory to then apply that to, to other, to other areas. And we know that, you know, the brain does not multitask. As much as we like to think that we multitask, you, people don't multitask. Uh, when you task switch from one thing to another, you end up wasting a, a lot of time as you adapt from one, from one task to the other. So if you're in some deep period of writing and you just stop to check your email, it'll take several minutes when you switch back before you get back into the same flow of the writing that you were doing before. So being able to be more fully focused on one thing because you, you offload tasks, say, with, to technology, I think could be very beneficial. Um, and there are other tasks that maybe didn't exist 10 or 20 years ago, or 50 years ago that, that now our brains are very good at. So recently somebody asked me about video games, and a lot of video games can involve, you know, uh, reactions, uh, fine motor control, problem-solving, um, all these things that we, we can sort of like be challenging our brains in, in, in, in a completely different way from how we might have done 100 years ago, but that doesn't mean it's not beneficial. I think that's very beneficial. It's just different.

Dr. Rangan Chatterjee 29:52 Different. You know what's really interesting on that? I heard over the past few months, you may know best for me 'cause I know you do some work with Formula 1, I believe one of the current top drivers-

Dr. Tommy Wood 30:03 Mm-hmm

Dr. Rangan Chatterjee 30:04 ... apparently was an avid video game player growing up. And actually, because of the way these cars are now controlled, hey, I'm no expert on this.

Dr. Tommy Wood 30:13 [laughs]

Dr. Rangan Chatterjee 30:13 This is just what I've heard from someone in Formula 1, that actually there may well be a lot of transferable skills-

Dr. Tommy Wood 30:20 Yeah

Dr. Rangan Chatterjee 30:20 ... from your ability to handle a video game controller and your ability to drive ... a Formula 1 car.

Dr. Tommy Wood 30:26 Yeah.

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Dr. Tommy Wood 31:19 One of the reasons why I said earlier that to some degree, maybe the challenge doesn't matter, like there's some specificity, but just increasing challenges on the brain may give you greater overall adaptability and function, um, is because we know that formal brain training, so like computerized brain training, which, which is used very frequently in, um, adults with cognitive impairment or cognitive decline because it's something that's very easy to standardize, systematize, easy to track, uh, so it's often implemented in clinical trials. If you do this sort of abstract online brain training games, um, it translates over to better working memory, executive function, and sort of things that you actually need in real life.

Dr. Rangan Chatterjee 32:06 Yeah.

Dr. Tommy Wood 32:06 Um, right? You're not... You don't just get better at the game, you also get better... There are transfer, the things that transfer. So, of course, video games may very, be very similar, um, to driving a Formula 1 car, but there is some, you know, just overall challenge increases overall function, which then does sort of translate to other areas.

Dr. Rangan Chatterjee 32:24 You mentioned the term executive function a couple of times in this conversation. Can you just elaborate exactly what that means?

Dr. Tommy Wood 32:31 In the simplest sense, uh, the way I think about executive function is your capacity to make informed decisions about your behaviors in the, in the moment, in the moment generally, and it's more complex than that. Maybe people have heard the old stories where we learned about different areas of the brain based on, uh, either soldiers getting very specific, um, damage to areas of the brain during war or the, you know, there was this very famous case where a guy got like a railway pylon that just like took out just his prefor- frontal cortex of his brain. And that guy, you know, just said whatever he thought, and it was very vulgar and very impulsive. Um, and executive function is essentially your ability to override those things. So like we all think stuff, and there's a part of our brain that says, "Don't say that."

Dr. Rangan Chatterjee 33:23 [laughs]

Dr. Tommy Wood 33:23 Right? "It's a really bad idea for you to say that." Um, or you know, you sort of have these, everybody has intrusive thoughts occasionally and you're like, "Well, what, what would happen if I just jumped out the window right now?" Right? Like I've, I've, I've randomly had that thought. It's a, right? But executive function is, "No, you really should not do that."

Dr. Rangan Chatterjee 33:39 Yeah.

Dr. Tommy Wood 33:40 Um, so it's those things which require... And it, it happens just a fraction slower than like the impulse, and it's your ability to control that and then sort of have some control over your actions.

Dr. Rangan Chatterjee 33:49 Yeah. So executive function is clearly a higher brain function that we would want-

Dr. Tommy Wood 33:55 Yes

Dr. Rangan Chatterjee 33:55 ... to maintain. We don't want it to be declining.

Dr. Tommy Wood 33:58 Yeah.

Dr. Rangan Chatterjee 33:59 Um, you know, [laughs] as you were saying that, I was thinking, you know, if, if you look around on, on social media these days, sometimes you, you see comments and I'm thinking, "You know that's a public comment, don't you?"

Dr. Tommy Wood 34:14 [laughs]

Dr. Rangan Chatterjee 34:14 You, you know other people are seeing that. I mean, that's just like, well, I guess it's off topic, but, but is it? No, that's kind of, that's an element of executive function.

Dr. Tommy Wood 34:23 I, I think so, and it's... I guess there's two parts to this, right? One is that, you know, you know, people talk about, um, the anonymity of social media. You know, you could just say stuff because there are no repercussions, right? Usually part of-

Dr. Rangan Chatterjee 34:38 Yeah

Dr. Tommy Wood 34:39 ... you deciding not to do something is because there's some social repercussion, which in general on social media, th- there isn't. Um, the other part of it, which I read about, um, uh, from Mark Manson, who's just one of my favorite or my favorite pop psychologist-

Dr. Rangan Chatterjee 34:54 Yeah

Dr. Tommy Wood 34:54 ... if you, if you wanna, if you wanna call him that, um, where he made the point that because of social media, you're exposed to the opinions of far more people than you would be otherwise, right? So 100 years ago when you couldn't have online interactions with people you essentially don't know, you might have seen 10 people in a day, and you might have seen 100 people in a week. Um, and some proportion of the population are probably people who aren't, who are gonna say things that you don't agree with or just aren't very nice, right? Um, but on social media you may be exposed to 1,000 or 10,000 people a day if you've got, you know, a lot of comments on social media. So part of it, I think is directly in relation to the how you might behave differently in social media rather than in person, and part of it is that you're exposed to so many more people that some of those people are just gonna be unpleasant and you're gonna see that.

Dr. Rangan Chatterjee 35:45 Yeah. If we get back to that family member who's retired, and so you were suggesting certain things that they could do to maintain that cognitive stimulus to reduce the likelihood that they're gonna get age-related dementia in the future. I know we touched briefly on this in our first conversation, but I think it's worth going into again, Tommy. It's not about mastery, is it? It's not about being an expert. In fact, in some ways you're better off doing something that you're not very good at. That's one thing I wanted to talk about, and then I wanted to sort of almost go from there to something practical for people because let's say we're trying to reduce the rate of decline in our brain function Something that I've been thinking a lot about over the past couple of years, maybe influenced by our first conversation as well, if I'm honest, Tommy, is what am I doing in the next five years of my life or in this decade of my life that is different and new and something I couldn't do in the last decade? And I, I think about this, like I have this thing inside me that at some point in the near future, I'm gonna take up martial arts because I'm fascinated by it. I've never done it before. I'll probably be pretty poor at it when I start, but for my brain function, that's probably a good thing, is it?

Dr. Tommy Wood 37:07 Yeah. And specifically related to martial arts, and there are-- so there are multiple different, um, sports where they've looked at this. But if you match the exertion level during ma- learning martial arts versus some other thing like running, right? We can get the same cardiovascular workout, but there's no movement or coordination challenge or, you know, having to think about not being punched in the face or kicked in the face if you're, you're actually sparring. You get a greater measurable benefit from the martial arts than you do from the running in terms of cognitive function, right? Because there's the additional challenge. Um, the question you asked about doing things that you're bad at, I think, is the perfect one because that then allows you to figure out the things that you might want to do, um, in, in order to increase the sort of stimulus, prevent the cognitive decline that we talked about earlier. And one of the best examples that I have of that is a study that was done in musicians, and they looked at how old their brains look on a brain scan. So you can do an MRI scan of the brain, and then there's this machine learning algorithm called brain age that basically says, how old does this brain look? You know nothing about this person, but how old does their brain look? And they did a study of musicians, and they had professional musicians and amateur musicians, and compared to the average population, all the musicians had brains that y- looked younger on the scan than they were in terms of their actual age in years. So being a musician seemed to be beneficial regardless of what type of musician you were. But the amateur musicians had a greater benefit. You know, statistically significantly younger looking brains compared to professionals because it's harder, right?

Dr. Rangan Chatterjee 38:48 Yeah.

Dr. Tommy Wood 38:48 If you're an amateur and you're not very good at it, then it's more of a challenge, right? That, that's what the conclusion that the authors came to.

Dr. Rangan Chatterjee 38:55 So there's an interesting conundrum here for me as I hear that, right? I'm thinking, okay, so someone may hear this and go, "All right. I'm in," right? "I'm gonna... I don't want my brain functions to go down."

Dr. Tommy Wood 39:08 [laughs]

Dr. Rangan Chatterjee 39:09 "I'm going to learn a new language."

Dr. Tommy Wood 39:11 Yeah.

Dr. Rangan Chatterjee 39:12 So they sign up for a course or they buy a book or whatever it might be, and they start learning that language and find out, "Oh man, this is really difficult. Oh God, I can't do this. This is really, really difficult. I've got a few words. I can't put it together in a sentence." Okay. If they persevere with that, that's gonna be great for their brain function. But I guess if they're not enjoying it because they're not good at it, they're probably not gonna do it much.

Dr. Tommy Wood 39:38 Yeah.

Dr. Rangan Chatterjee 39:38 So, you know, help, help, help us understand practically what we should do in that, in that situation.

Dr. Tommy Wood 39:45 And that- that's absolutely right. So I think the, the process of learning and failing, um, developing a skill that you can probably only do in 20 or 30 minute chunks. If you think about a martial arts class, after you've warmed up and the warm down and the stretching, like how much time are you spending learning new patterns, new movements? It's maybe 20 or 30 minutes in a class. If you are-- If you do a language class, you know, after you've, uh, said hello to everybody and kind of got into it and opened the books and, you know, you have a couple of conversations, how long do you really spend sort of pushing the limits of your language skills? It's maybe 20 or 30 minutes in an hour. 'Cause that's really the period of time when a-- when humans can really sort of like push on the edges of their skill. So if you think about learning new skills, then that's, that's kind of what you're thinking about. Something that you can spend 20 to 30 minutes, you know, really sort of exploring the limits of what you can currently do, getting a little bit better and that's it, right? It should be hard after that. And then, you know, you get frustrated or you get cognitively tired, and that's when you need to rest and recover. What you choose to do that I think matters a lot less because of all the things we, we talked about. Language, we talked about movement. You know, it could be like knitting, um, it could be video games, it could be online brain training. All of these things have been shown, uh, to have benefit.

Dr. Rangan Chatterjee 40:59 Yeah.

Dr. Tommy Wood 40:59 And so, yes, just doing something that's hard is gonna be, is gonna be beneficial to a certain extent, but if it's not something where you can continuously go back to it-

Dr. Rangan Chatterjee 41:08 Yeah

Dr. Tommy Wood 41:08 ... um, 'cause you enjoy it, then you're, you're not gonna stick to it. So it's the thing, you know, it's a combination of something where you are learning over time and getting better, but also something that you enjoy because that's the thing that you're gonna do more of.

Dr. Rangan Chatterjee 41:20 Yeah. So that's super practical for all of us, whether it's our retired parents or, or ourselves. It's like, what are we doing in our lives currently that is challenging and that we enjoy?

Dr. Tommy Wood 41:35 Yeah.

Dr. Rangan Chatterjee 41:35 I guess, and you are saying this sort of 20 to 30 minute period. Are there any specific trials on that, or is that sort of an amalgamation of other neuroscience research that that means, yeah, we kind of think it's about this time?

Dr. Tommy Wood 41:49 Yeah. It's, it's probably, um, at least partly related to, you know, focus and attentional capacity. And in other areas you see something, you see some- something similar. So I'm, I'm s- I'm stealing ideas from, say, the Pomodoro technique, which is where you have, uh, 20 or 25 minutes of focused work with then a five minute, five minute break where you completely detach yourself because 20 minutes is, is the period of time where you can really focus on, on something and, and devote yourself to it before, again, you, your mind starts to drift or you, you go elsewhere. And then if you think about, well, in scenarios where we're teaching people new skills, you know, of course, you're, you're usually trying to fit something into an hour because that's just like the standard unit of time. But in general, like how long are people really working on these things? And it seems to be something like 20 to 30 minutes. So part of it's practical, but then part of it is based around, on average, that's the period of time when sh- uh, somebody can really focus on something.

Dr. Rangan Chatterjee 42:44 Crosswords, Sudoku, do they help?

Dr. Tommy Wood 42:50 I don't... My guess is a little bit, but probably not nearly as much as any of the other things that, that we've talked about, um, purely because there just isn't that kind of, there isn't that kind of challenge or skill in the same, in the same way. Um, maybe cryptic crosswords are their own [laughs] separate... Because there's, there's, um, there's a skill around cryptic crosswords, right? You need to know what the clues are for what you need to do with either the words or the letters, um, in order to, to, to get the final word. Um, a traditional crossword is usually just memory, and yeah, that could, that can be useful, but it, it's not, it's not that same kind of challenge. And then again, once you're good at it, so once you're really good at cryptic crosswords, it's probably not the same challenge anymore. Once you're really good at Sudoku, it's probably not the same challenge anymore. And people often like to do, um, those things because they're, you know, it takes five or 10 minutes, it passes some time.

Dr. Rangan Chatterjee 43:45 Yeah.

Dr. Tommy Wood 43:45 It's nice to complete something. But then you're in some area where it's not really the same kind of challenge. So, so maybe, but probably not the same way as some of those sort of more all-encompassing skills that we've talked about.

Dr. Rangan Chatterjee 43:55 Yeah. I love this, Tommy. It's, it's super practical. I know we spent a lot of time on this kind of, um, how are you stimulating your brain in a new way, in a novel way that's challenging. We'll definitely talk about food and sleep and movement-

Dr. Tommy Wood 44:10 [laughs]

Dr. Rangan Chatterjee 44:10 ... and stress and that stuff. We- we're definitely gonna get to that. But I think it's worth, I think it has been worth really hammering home this point.

Dr. Tommy Wood 44:16 Yeah.

Dr. Rangan Chatterjee 44:17 Um, in terms of looking at what we can do to prevent our brain function going down with age, I love the way that I've heard you think about this before, and say the reason we know what to do is because we know how to create cognitive decline in animal models.

Dr. Tommy Wood 44:38 Yeah.

Dr. Rangan Chatterjee 44:38 And I thought that's a really beautiful way of us looking at it. So perhaps you could explain your framework, and then we could see where we're up to and where else we need to go.

Dr. Tommy Wood 44:48 Sure. So again, like I mentioned earlier, uh, in my day job, I'm a neuroscientist, and the vast majority of that is doing work in animal models of brain inj- of brain injury and brain disease, neurodegeneration. I think what you see is that, you know, from those models... And, and what's nice about those models is you can isolate a single thing. So I've been talking, I've been having conversations about this recently, um, in relation to, you know, what do you need, you know, what's important for cognitive decline? What's causative in humans? Um, and I've had some conversations around, uh, the work of David Smith, who's a, a emeritus professor from, uh, Oxford who ran, you know, groundbreaking trials showing that if you give B vitamins to lower homocysteine, um, in humans who have elevated homocysteine, you can slow the rate of brain atrophy and cognitive decline, like just with a simple, uh, with a simple multivitamin. Uh, and they, the- then there's a interaction with, uh, omega-3 status as well. So nutrition, incredibly important. But then there's a question of the homocysteine, which is the thing that you measure to decide whether this person needs this supplement or not. Um, is the homocysteine damaging itself or is it just telling you something about this nutrient deficiency? Um, and that's a question that we can't answer in humans because you can't dissociate the marker, the thing itself, from what's causing it to be elevated.

Dr. Rangan Chatterjee 46:08 Yeah.

Dr. Tommy Wood 46:08 You can do that in animals. Um, I don't think it's been done in a way that sufficiently a- answers the question that I have, which is that is it just the B vitamins or does the high homocysteine itself have a, uh, have a causative effect on cognitive decline? And some people think yes, and some people think no. But that's an, a question you can only answer in animals. Um, but more broadly, you need, um, you know, there are essentially three different ways that you can create cognitive decline in animals, and that's not doing genetic manipulation. That's kind of... I'll keep that separate. Assh- assume that you just have, um, a he- an otherwise healthy rat or mouse. You can, um, decrease the supply of things that are important for the brain, and you can do that in two ways. You can either decrease the amount of those things being around, so nutrients being one. We just talked about some. Or you can decrease the flow of blood and oxygen to that area of the brain. You can create, like, a chronic, um, decrease in blood supply to the brain. And so you're either not providing enough of the nutrients or those nutrients ar- aren't able to get there. That's, that, that's one thing that's imp-

Dr. Rangan Chatterjee 47:15 So, so on that one thing, that's, uh, for a human, that's a poor diet.

Dr. Tommy Wood 47:19 Yes.

Dr. Rangan Chatterjee 47:20 Not getting enough nutrients in to supply-

Dr. Tommy Wood 47:22 Yeah

Dr. Rangan Chatterjee 47:22 ... the brain, or it's having, again, a non-scientific term, but furred up arteries-

Dr. Tommy Wood 47:29 Yeah

Dr. Rangan Chatterjee 47:29 ... so that, you know, you can't deliver as many of those nutrients that you may be taking in to that part of the brain. But that's all part of that first-

Dr. Tommy Wood 47:39 Yes. Exactly

Dr. Rangan Chatterjee 47:39 ... thing that you can do-

Dr. Tommy Wood 47:40 Yeah

Dr. Rangan Chatterjee 47:41 ... to cause problems.

Dr. Tommy Wood 47:42 Yes.

Dr. Rangan Chatterjee 47:42 Okay.

Dr. Tommy Wood 47:42 So yeah, so the, uh, any kind of vascular supplies, so it could be, and it can happen in the arteries in your neck, arteries in the brain, and it's usually, you know, it's the same kind of process that happens in the arteries in the heart. It might lead to a heart attack.

Dr. Rangan Chatterjee 47:53 Ca- can we just pause on that a second, Tommy?

Dr. Tommy Wood 47:55 Yeah.

Dr. Rangan Chatterjee 47:55 Because a theme I think throughout this conversation is that you may not get the diagnosis of age-related dementia or Alzheimer's till you're 65 or 70, but the process that leads to that diagnosis may well be starting in your 30s or your 40s. I know Professor Dale Bredesen, who I've spoken to before on many occasions, um, the neurologist in America, he, I'm pretty sure he said, you know, it, this starts at least 30 years beforehand in the brain.

Dr. Tommy Wood 48:27 Yeah. Yeah. Exactly.

Dr. Rangan Chatterjee 48:29 So I think that's a key point. So we're gonna talk about diet shortly. And also in terms of nutrients getting up, again, people may be familiar with strokes or heart attacks, where that's a very late stage when actually you've got problems and symptoms. But many of us probably, without realizing, may well have degrees of furring- Well before that?

Dr. Tommy Wood 48:51 Yeah. And so everything happens on a, on a continuum. And you can ... Yeah, you, you might have this, you know, acute, very acute change or lack of blood flow. That's what we would call, uh, a stroke, an ischemic stroke. Um, but you can also just have, um, it ... And it may not even be, right, if you had a, a, a scan on your arteries. You may not even see that there's this huge blockage or anything like that. But over time, again, as your vascular system, you know, your, your, your blood vessels, as they age, and that's related to a whole bunch of these very similar things, um, they become more stiff. And when they're more stiff, they ... It means that they can't regulate themselves the way they normally would. And we, we do this process in the brain called neurovascular coupling, which basically says that when a neuron is more active, it asks for more blood flow, right? I'm gonna ... And the muscles do the same, right? When you work your muscles harder, your body diverts blood to those muscles, and the brain should be the same way. But over time, the blood vessels may not be able to do that. So when the brain is asking for more oxygen-

Dr. Rangan Chatterjee 49:54 Mm

Dr. Tommy Wood 49:54 ... or it's asking for more nutrients, the vessels don't respond. Um, so that's, so that's kind of one thing. You're not getting enough of whatever it is you need-

Dr. Rangan Chatterjee 50:01 Okay

Dr. Tommy Wood 50:01 ... to the, to the, to the point. Then another way is to provide some kind of chronic, for want of a better word, toxic exposure. Uh, some-

Dr. Rangan Chatterjee 50:12 So this is the second way to damage-

Dr. Tommy Wood 50:13 Yes

Dr. Rangan Chatterjee 50:13 ... your brain.

Dr. Tommy Wood 50:14 This is the second way to create cognitive decline in a, in a, in an animal model. Um, and, you know, they ... You can sort of like poison very specific parts of mitochondria or other things. So like very small ... Like, they've done it with very small doses of cyanide, uh, but you could equally do it, uh, by exposing, uh, uh, an animal to, um, like exhaust, car exhaust. Um, you know, sort of more common things that, that we know are part of the environment. And so those things essentially inhibit, uh, either energy production or the ability of the, the cells in the brain to res- to, to respond or, or adapt or may be directly damaging.

Dr. Rangan Chatterjee 50:50 So toxic exposures, so it could be cigarette smoke.

Dr. Tommy Wood 50:53 Yeah.

Dr. Rangan Chatterjee 50:53 It could be car exhausts. Um, it could be heavy metals-

Dr. Tommy Wood 50:58 Yeah

Dr. Rangan Chatterjee 50:59 ... in fish.

Dr. Tommy Wood 50:59 Um, uh, either ... So heavy metals in fish, so potentially mercury. Although, if it comes from fish, the selenium and the omega-3s and things like that in the fish may-

Dr. Rangan Chatterjee 51:09 Protect us

Dr. Tommy Wood 51:10 ... yeah, may protect us and sort of overcome any, any detrimental effect there. Uh, but something like lead seems to be, um, you know, a poten- And it's very common in, in some water supplies, even in, you know, i- industrialized countries. So, so-

Dr. Rangan Chatterjee 51:22 I think for years it was in the paint.

Dr. Tommy Wood 51:23 Yeah, yeah. In the paint, in the pipes.

Dr. Rangan Chatterjee 51:26 I mean, we're-

Dr. Tommy Wood 51:27 It was in, in ... So it was, it was ... That was part of air pollution, right, 'cause of leaded petrol.

Dr. Rangan Chatterjee 51:31 Of course. I mean, we're only two into the three ways in which you can cause-

Dr. Tommy Wood 51:36 There's actually a fourth. I forgot there's actually a fourth.

Dr. Rangan Chatterjee 51:37 There's a fourth, right?

Dr. Tommy Wood 51:38 Yeah.

Dr. Rangan Chatterjee 51:38 So we're only two of the ways in, and I'm already thinking about what you said at the start about the societal pressures and, you know, poor nutrition, poor lifestyles, um, air pollution, right?

Dr. Tommy Wood 51:51 Yeah.

Dr. Rangan Chatterjee 51:51 It ... We're ... [laughs] It's no wonder when we currently study populations-

Dr. Tommy Wood 51:54 Yeah

Dr. Rangan Chatterjee 51:54 ... like there's a linear decline in, in our brain function.

Dr. Tommy Wood 51:57 Yeah.

Dr. Rangan Chatterjee 51:58 So with all the good news, let's go for-

Dr. Tommy Wood 52:00 [laughs]

Dr. Rangan Chatterjee 52:00 Let's, let's go to number three.

Dr. Tommy Wood 52:01 It's lack of, it's lack of stimulus, right? So we've already talked about that-

Dr. Rangan Chatterjee 52:04 We've talked

Dr. Tommy Wood 52:04 ... in mul- in multiple ways. But if you ... Um, the way that we would do that in animal models, um, is we either socially isolate an animal, which is incredibly stressful, and you have to get ... Um, what, what's interesting, and it's im- it's import- I mean, it's incredibly important for doing high quality animal work that's ethical and that actually helps us move human health forward, which is ultimately the goal. If it's not doing that, I don't think it's worth doing. Um, that, you know, in order to do ethical animal work, you have to, you know, look after those animals as best as you possibly can. And one of the ways that that's ensured is, you know, there are committees at every university that make sure that every experiment that's proposed is, is sort of as, as, um, ethically sound as possible. But unless you have a really good reason to, there are two things you're not allowed to do. You're not allowed to socially isolate the animal, and you're not allowed to remove any stimulus from the environment, what we call environmental enrichment. And that can be in terms of, uh, like a running wheel for mice, or it could just be like toys or something in the cages. Um, and if you think about humans, socially isolated, lack of cognitive stimulus, like we're doing this to vast proportions of our population, particularly as they get older and we've taken away social connection, we've taken away stimulus. Um, you're not allowed to do that to a rat in a lab unless you have a very good reason for doing it.

Dr. Rangan Chatterjee 53:24 That-

Dr. Tommy Wood 53:24 But you can do it to a human no problem.

Dr. Rangan Chatterjee 53:26 That is ... Just to look at it through that lens is completely nuts, isn't it?

Dr. Tommy Wood 53:30 Yeah.

Dr. Rangan Chatterjee 53:31 Wow.

Dr. Tommy Wood 53:32 So that's, that's the third part. And then the fourth part, uh, we kind of talked about a little bit as well, which is that, right, you need the stimulus, you need the things that are required, nutrients to respond to the stimulus, you need the absence of toxins, and then you need some kind of period of rest and recovery. So that's why sleep is critical. But then also, um, absence of chronic stress is probably something you could put into that bucket as well. And, um, you can do this, uh, with social stresses, say, um, in, in ... if you're gonna do this in, in an animal model. Um, so we, we talked about social isolation. That's, that's, that's a chronic stressor. But you can also do it with, um, aggressors. So you might have a- an aggressive, um, mouse that you introduce into the cage, and then that continuous aggression, which, uh, could be, uh, discrimination based on your physical ability, based on your race, based on your socioeconomic status. You know, these things that people are exposed to again and again and again, and we might model it in that way. And then that's ... You know, there's a whole host of, um, physiological, immunological, you know, things that we can measure that result from that. But, you know, cognitive decline and chronic health conditions can be one of the things that come from that.

Dr. Rangan Chatterjee 54:41 Yeah. I'm thinking of that aggressive boss, that aggressive family member.

Dr. Tommy Wood 54:46 Yeah.

Dr. Rangan Chatterjee 54:46 The, the sort of thing we can all think about in our own lives, whether currently or previously, and what an impact that can have. And it also speaks to what you said earlier on in the conversation, and it's something we have to be super conscious of when we're talking about- Making changes to improve the quality of our lives. You know, I'm all, like you, for empowering people with helpful information, but I think we do need to acknowledge, maybe in this wellness community more than often does get acknowledged, that there are huge psychosocial stresses-

Dr. Tommy Wood 55:16 Yeah

Dr. Rangan Chatterjee 55:16 ... cultural stresses for different communities, financial stresses, racial stresses. These things hugely impacts our biology and our physiology.

Dr. Tommy Wood 55:26 Yeah.

Dr. Rangan Chatterjee 55:26 And for some of us, it's easier to make those changes than for others, isn't it?

Dr. Tommy Wood 55:31 Yeah. And, uh, I think it's, uh, it's been something that's sort of aimed at, uh, whether you ca- you know, the lifestyle medicine or, uh, functional medicine or integrative medicine, uh, ancestral health communities. You know, those people who focus on these lifestyle factors that we've talked about. And it's a worthy critism- criticism to say not everybody can do that, right?

Dr. Rangan Chatterjee 55:52 Mm.

Dr. Tommy Wood 55:52 Not everybody has the financial ability to remove themselves from the environment that they're in, if it's, you know, um, they have to live close to a road, or they have to live close to a refinery, right? So in, in, in the, in the United States, um, you know, near, you know, large petrochemical plants, that's where you've had redlined housing areas where people from low socioeconomic status, usually more likely to be Black, have been put-

Dr. Rangan Chatterjee 56:14 Mm

Dr. Tommy Wood 56:14 ... around these areas. And then it's, you know, it's baked into the environment, and you can't afford to move out. Um, and or it may be, you know, we talked about food, but, you know, what food to- do you have access to? Um, do you even have a kitchen? You know, do you have-

Dr. Rangan Chatterjee 56:28 Yeah

Dr. Tommy Wood 56:28 ... are you working two jobs and do you, do you have time to cook? Um, you know, we need to be very mindful that the social determinants of health play a big role here.

Dr. Rangan Chatterjee 56:36 Yeah. Uh, I mean, I totally agree with that. I, I think it's ... I think there's a lot of nuance to that because sometimes that criticism gets leveled and say we shouldn't be giving any information out because it's not relevant to that community.

Dr. Tommy Wood 56:48 Yeah.

Dr. Rangan Chatterjee 56:49 I don't agree with that.

Dr. Tommy Wood 56:50 No.

Dr. Rangan Chatterjee 56:50 It's like, we should definitely be giving out information, but we also need to be aware that that information may not be relevant or as relevant, and so we shouldn't look down when people can't take that advice, for example.

Dr. Tommy Wood 57:04 Yeah.

Dr. Rangan Chatterjee 57:04 You know, and I've always fought for that, uh, wellness, for want of a better term, is for everyone. I think every single human being has the right to good, quality health information that they can try and apply in their own life. And my bias comes from my clinical practice. So, um, I, I've worked in lots of different practice throughout my career, but there was a particular period of time where I worked in a practice in Oldham, in North Manchester, and it was a very low socioeconomic status area, lots of immigrants, lots of people on benefits, people working two jobs, lots of single parents. A lot of, in inverted commas, struggle for day-to-day life compared to other areas I've worked where it's, um, you know, more affluent.

Dr. Tommy Wood 57:50 Yeah.

Dr. Rangan Chatterjee 57:50 Now, there's struggle there as well in a different way. And you know what I learnt, Tommy, in that, is that ... Because I think it's easy, and I see this in the media a lot, we ... It's either we can empower people with their lifestyle choices, or we say that there's huge social determinants of health. It's kind of like, well, why does it have to be that black or white? I think all these things are nuance-

Dr. Tommy Wood 58:11 Yeah

Dr. Rangan Chatterjee 58:11 ... and I'm ... I, I do passionately believe that this information is relevant for everyone, and we should be giving it to everyone, but with the acknowledgement that for some people it's harder.

Dr. Tommy Wood 58:21 Yeah. And, and I completely agree. And I, in that line, I think it's very both patronizing and disempowering to say-

Dr. Rangan Chatterjee 58:29 Yeah

Dr. Tommy Wood 58:29 ... that, "Oh, you shouldn't be talking about lifestyle or diet because it's ... you know, these people m- you know, may, may or may not have an ability to change that."

Dr. Rangan Chatterjee 58:37 It's very condescending.

Dr. Tommy Wood 58:38 It's incredibly condescending. So but we just need to acknowledge that all of these things are important. Um, but again, there have been the ... There was a, a recently published study came out in, in Lancet Public Health a few years ago that looked at, using UK Biobank data, looked at, like, uh, mortality risk. Um, and they stratified individuals by some lifestyle factors, so based on quality of diet, whether they smoke, you know, physical activity, and then also stratified them by social deprivation. And you see that, yes, as your, um, like, socioeconomic status decreases, overall risk increases.

Dr. Rangan Chatterjee 59:11 Mm.

Dr. Tommy Wood 59:11 But when you look at the effects of lifestyle, movement, diet, there's still great benefit there.

Dr. Rangan Chatterjee 59:17 [laughs]

Dr. Tommy Wood 59:18 So, so, yes, the overall risk is greater, but you can ... Like, those, there are individuals there, you know, reducing it through those, through those activities. So to say that we, we shouldn't be talking about it, I think, is incredibly condescending.

Dr. Rangan Chatterjee 59:29 A- a- and also, you know, what I found, Tommy, is that if I change the advice I give them because I make that assumption, I'm depriving them of good quality advice. And what I learnt there is actually sometimes in the poorest communities, they would actually literally follow my advice to the letter more-

Dr. Tommy Wood 59:47 [laughs]

Dr. Rangan Chatterjee 59:48 ... than in more middle-class, affluent communities. Like, I remember, I thought that, you know, there wasn't much money in the family, and, you know, at the time, I don't think we were allowed to give vitamin D. This lady had really bad pains, and I was convinced it was related. And, um, you know, she went and bought from the local health food shop supplements for her and her family and got huge improvement. And, like, it's unfair to, to think that we know what they will prioritize-

Dr. Tommy Wood 1:00:17 Yeah

Dr. Rangan Chatterjee 1:00:17 ... with their money. It's not up to us. Yeah, I think this is, this is complex, but I think it's important that we talk about it actually.

Dr. Tommy Wood 1:00:23 Yeah. A- a- absolutely. Um, uh, all of the, all of these pieces are ... you know, different parts are, are important for different people in, in, in different amounts. And, um, there's ... You know, part of it is just getting information out there. And, and so, uh, again, empowering people to, to know what may or may not be important, uh, for them, for ... And it could be whether they're worried about their risk of dementia or heart disease or, you know, they just wanna be able to play with their grandkids. Uh, you know, you know, often people's goals are, uh, much more practical than a doctor might think. You know, you're, you're worried about some diagnosis or something, but people, you know, wanna be able to just interact with their family or something like that. And different things are gonna be a different relative importance for different people, but they should be allowed to, to make those decisions.

Dr. Rangan Chatterjee 1:01:03 Yeah.

Dr. Tommy Wood 1:01:03 And, you know? Yes, we sh- I, I think that, um, we need greater support For behavior change for individuals who want it, um, we don't necessarily-

Dr. Rangan Chatterjee 1:01:14 Sure

Dr. Tommy Wood 1:01:14 ... do a good job of that.

Dr. Rangan Chatterjee 1:01:15 And doing something new that's stimulating and challenging, there are a lot of low-cost ways to do that.

Dr. Tommy Wood 1:01:21 Oh, completely free.

Dr. Rangan Chatterjee 1:01:22 If not free ways to do that.

Dr. Tommy Wood 1:01:23 Absolutely. Yeah, absolutely.

Dr. Rangan Chatterjee 1:01:24 You know? Balancing, hopping around your ... You know, I don't know. We could make up all kinds of things that would actually provide a stimulus.

Dr. Tommy Wood 1:01:29 Yeah, absolutely.

Dr. Rangan Chatterjee 1:01:30 And, and so I think that's a great piece of practical advice. Okay, so that was in the first bucket. The second bucket was about important nutrients not getting to the brain, whether that be 'cause we're not taking them in, or because we're taking them in, or we might be taking them in, but they're not able to get to where they need to get because, let's say our, our blood vessels are in poor health for whatever reason. So you've been on a bit of a journey, Tommy, since I've known you and from what I've seen in public. Um, as we have this conversation in 2022-

Dr. Tommy Wood 1:02:04 [laughs]

Dr. Rangan Chatterjee 1:02:05 ... uh, what is your current viewpoint on nutrition for human health? Uh, I guess specifically we're talking around brain health-

Dr. Tommy Wood 1:02:16 Yeah

Dr. Rangan Chatterjee 1:02:16 ... preventing cognitive decline as we get older, which I think everyone wants. What kind of advice would you give to people regarding foods?

Dr. Tommy Wood 1:02:24 I think the, the starting point is that you should eat something that is accessible to you, that you enjoy, and is sustainable. Like, that has to be a, a starting point because I could give you a whole bunch of recommendations, but if it's none of those things, then you're not gonna do it or not gonna stick to it. And one thing that constantly fascinates me about the human body is how adaptable it is. Um, and the wide variety of diets that people, um, evolved while eating or, you know, ancestrally, you know, the, the different diets that, you know ... My ancestors ate a very different diet to your ancestors just because of where they are on the planet, and they both thrived, and I find that fascinating. And so it, the ... It's the same thing now. Like, what somebody enjoys and is sustainable to them is very different from the person next to them, and they may sustain their health in, in an identical manner with, you know, objective, objective measures that you could take. So I don't have any particular one way that I would recommend that people eat, but it should support your health, and we can certainly talk about things that you might measure, uh, and want to, to track, um, over time. Specifically for the brain, uh, because we have interventional studies that, that show it's the case, um, B vitamins are incredibly important, so we're talking, um, B12, which generally you can only get from meat and animal foods. Um, if you are vegetarian or plant-based, I think the best people who, uh, promote or work with individuals with those diets would recommend you take a B12 supplement. Um, then, uh, folate, uh, uh, B2, which is riboflavin, and, uh, B, B6. Those are probably the most important, uh, nutrients for, for, for, for brain health, and again, you know, any diet that has a, a reasonable number of whole foods, plants, vegetables, eggs, meat, fish, will have enough of those probably. Um, then the other important thing specifically, uh, for the brain is, uh, uh, the omega-3s, long-chain omega-3s, and in this, in these studies that I mentioned earlier, uh, by David Smith, they showed that the greatest benefit from the B vitamin supplement came from those who had what they called adequate omega-3 status. And again, so these are long-chain, um, omega-3 fatty acids like EPA and DHA, which in the diet are generally only available from seafood. Uh, but there is a g- there is a slight genetic component based on people who can take shorter ones that you might get in chia seeds or walnuts and then convert them to, to longer chain ones. Um, but, uh, so again, there's, there's, there's, there's a slight genetic component there, but some seafood is probably important as well.

Dr. Rangan Chatterjee 1:05:08 Yeah. Okay. This, this is super interesting. So you first mentioned B12, and as you say, if people are eating animal products in their diet, they're likely to be at least taking in enough B12. What I've found, wanting to measure this quite a lot, is that even people who were taking in reasonable amounts of B12 had suboptimal B12 levels on their bloods.

Dr. Tommy Wood 1:05:35 Yeah.

Dr. Rangan Chatterjee 1:05:36 There's a whole variety of reasons why that might be. Uh, I have my view. I, I feel ... I certainly feel stress is a huge part of it because to be able to actually absorb that B12, what needs to happen can be impaired, I think, by too much stress. Because I was thinking, why is it that they're eating enough B12 from what I can tell, yet that's not being shown up? And, and there's all kinds of reasons for it. That's just one of my views. I mean, what, what's your perspective on that? Is that something you've seen, and do you have any opinions as to the reasons why that might be?

Dr. Tommy Wood 1:06:08 Yeah. Um, uh, absolutely. And I, I remember even, um, you know, 10 years ago, uh, it's now 10 years since I worked as a doctor pretty much, uh, as a junior, junior doctor at St Thomas' in London. I was working on the elderly care ward, and when people got a, a first diagnosis of dementia, even then one of the first things we did was, uh, something called a dementia screen, which we looked at iron status, uh, vitamin D, and some, uh, B vitamins, B12 and folate at least. And then if f- um, B12 was low, there was a second test they call methylmalonic acid, which is produced, uh, when you're B12 deficient. And so even then we were doing it in an NHS hospital 10 years ago.

Dr. Rangan Chatterjee 1:06:47 Yeah.

Dr. Tommy Wood 1:06:48 Right? Just these basic nutrient sta- status checks. And I think, uh, stress is, you know, stress, um, certainly may affect, um, acid production, which is really important for B12 and also iron absorption. Um, but then some medications can do it. So metformin can, can affect B12 absorption. Uh, proton pump inhibitors, which people might take for, um, you know, reflux, that can affect, uh, B12 absorption, and these are very common drugs-

Dr. Rangan Chatterjee 1:07:13 Yeah

Dr. Tommy Wood 1:07:13 ... uh, to prescribe. So, uh, you know, there's probably some, some lifestyle factors, but then, uh, you know, it, it may also be a result of some- something else that somebody's taking.

Dr. Rangan Chatterjee 1:07:21 Yeah, I remember Professor Bredesen when I spoke to him about this a few, a few years ago. He, he will work with his patients to do all the tests, the homocysteine, the, the MMA that you mentioned, and the serum B12. And at the time, I remember thinking, "I, I can't get this stuff for my NHS patients" back then. And he said he likes to see, for cognitive function, a serum B12, right? So that's your regular cheap, uh, B12 test. Um, and, you know, I'm gonna say it depends on your lab, but, you know, the normal value that will be reported would typically be something like 200, 250 to 700, 800, maybe 900-

Dr. Tommy Wood 1:08:04 Yeah

Dr. Rangan Chatterjee 1:08:04 ... depending on the lab.

Dr. Tommy Wood 1:08:04 Yeah.

Dr. Rangan Chatterjee 1:08:05 Right? So huge, huge range of normal.

Dr. Tommy Wood 1:08:07 Yeah.

Dr. Rangan Chatterjee 1:08:08 And he said in his experience, if it's under 600, he would treat it.

Dr. Tommy Wood 1:08:12 Mm-hmm.

Dr. Rangan Chatterjee 1:08:13 And I remember I came back, 'cause I ... I was chatting to him in America, and I, I tried that with a few patients actually. And again, this is just anecdotal. It's not a scientific study. But people would come back and say, yeah, they feel sharper, their cognitive function has got better when I'd treat their serum B12 from, let's say, a normal level of 250. What do you think to that?

Dr. Tommy Wood 1:08:34 I think that's, um ... I mean, I'm, I'm not necessarily surprised. Uh, again, it depe- probably depends ... What's interesting about, um, the difference between the US and the UK is that in the US you can't get an active B12 test, what we would call holotranscobalamin, is very common to do in the UK. You can't do it in the US. So you ... In, on the US test, you probably need to be at the h- at the upper end of normal because, um, there are lots of other things that can cross-react with the test, and they look like B12, but they don't have the function-

Dr. Rangan Chatterjee 1:09:09 Mm

Dr. Tommy Wood 1:09:09 ... of, of B12, and that's the case with some, like, plant-based B12 analogues. Uh, so that ... So for him, I, I imagine that's probably one reason why that may be the case. But equally, more broadly, I spent a lot of time, uh, looking at, uh, looking at and thinking about blood tests. And if we think back to what we said right at the beginning, which is that the average popula- the, the average adult has at least one chronic condition, takes at least one, um, medication, has at least one, if not two, of the components of metabolic syndrome, of which there are five. If that's the average person, and the normal range is just ... The way you define the normal range is you test a whole bunch of people, and you take the middle 95%.

Dr. Rangan Chatterjee 1:09:54 Mm.

Dr. Tommy Wood 1:09:54 And whatever the bottom, the lowest person of that middle 95% and whatever the top person is, that's the normal range. And if the average person is sick to some degree, then what's normal is not necessarily normal. Um, and I think that's part ... And you, you see this again and again, um, the ... They've changed the ranges over time. That's been, uh, it's been the case for certain sex hormones, you know, like ... And people have talked about this a lot. You know, they, they're decreasing the normal range for testosterone in men because they think that testosterone is de- decreasing, um, on ... at, at the population level. Whether that's actually true or not is up for debate, but it's something that's happened. That's, you know, they've changed the ranges if they see that, you know, the overall the population level changes. I saw something similar when they were trying to develop normal ranges for grip strength. Um, and what they saw over, you know, generations, you know, from, you know, like, uh, Generation X, uh, Generation Y, Millennials, like, uh, coming through to what w- in America we call Gen Z.

Dr. Rangan Chatterjee 1:10:55 [laughs]

Dr. Tommy Wood 1:10:56 Um, grip strength was declining, particularly in males. So there was a publication that said that and said, "We need to change the normal range for grip strength," rather than saying, "We're getting weaker. Why aren't we working on that?" And so, you know, it's, it's like, um, the, the frog that sits in water from-

Dr. Rangan Chatterjee 1:11:14 [laughs]

Dr. Tommy Wood 1:11:15 ... when it's cold, and then if, if you bo- if you boil it, it will slowly heat up. It will never jump out, right, because it never realizes-

Dr. Rangan Chatterjee 1:11:20 Yeah

Dr. Tommy Wood 1:11:20 ... because it's so incremental and slow. And so that's, that's one of the problems, is that we're look ... You know, some normal ranges are constructed around a population that's sick, so then normal isn't necessarily, isn't necessarily normal, and that's p- that may be playing part of the role there too.

Dr. Rangan Chatterjee 1:11:33 Yeah. It, it, it's super interesting, and hopefully we'll get time to go into some blood tests that people can do. You mentioned seafood. Why do you think seafood is so important for our brain health?

Dr. Tommy Wood 1:11:44 Mm-hmm.

Dr. Rangan Chatterjee 1:11:45 And then for people who are vegan or, you know, choosing not to have animal products, can they still have good brain health and get those nutrients that you would get from seafood in other ways?

Dr. Tommy Wood 1:12:02 So there are a few strands, um, the m- the m- the ... of information that lead me to think that, that seafood... Or I say seafood because it's the, the most common dietary, um, component that gives us long-chain omega-3s. What I'm really interested in is long-chain omega-3s, particularly DHA in the brain. And again, if I go back to what does it take to build a healthy brain in the first place, DHA is preferentially sucked up into the brain while you're making it, as much that the mother will sacrifice her own DHA status so that the baby gets enough. Because it's one of the most critical fats that makes up the brain, for a number of reasons. Um, it ... And it goes, it goes directly into the, the cell membrane. So people may or may not know that most of your brain, which isn't water, is fat. Almost all of it, right? So because fat makes up all the, uh, insulation around the nerves. It makes up all the, the membranes around the cells. And DHA is incredibly important both for the function of the synapses, how they talk to each other, because of its ... Because of the, because of its structure, it has this, you know, very important, um, role in terms of, like, how the synapses work, how neurons talk to each other. But then it's also accumulated into the mitochondria, which people might know as the powerhouse of the cell. It sits inside the cell, generates most of the energy. And some of it is really cool physics that basically how electrons travel through DHA is really interesting. Um, but equally, you know, sort of like a more basic way, you can see that the more DHA that's in a mitochondria, the greater energetic capacity it has, the more energy it can produce. Um, and that's the reason why... And, and there are some evolutionary theories that say that, you know, maybe the human brain as it currently exists, developed in a sec- i- in, like, a group of hominids that had either di- direct access to lots of seafood or to the brains of other animals, uh, because brains are an incredibly rich source of DHA because your, your body preferentially shuttles it, uh, to the brain during development. So, it has this really important functional role. Um, and when you, um, don't have it, that's associated with neurodevelopmental disorders or developmental delay, um, risk of other neurod- uh, like neurodevelopmental issues. Um, and then you can also see things like, um... There have been some interesting studies done in the UK and in the Seychelles where, uh, you look at the, the amount of seafood that a mother or her ba- uh, her children eat, and then you look at long-term neurodevelopment. And you, you asked about heavy metals earlier, particularly mercury is important for seafood. But it seems that even if you have a higher mercury burden because you eat a lot of seafood, you get a, you get greater benefit-

Dr. Rangan Chatterjee 1:14:47 Yeah

Dr. Tommy Wood 1:14:47 ... uh, because of the omega-3s in the diet. Um, so that kind of, you know, that sort of first principles approach says, w- what does a brain really want when it's developing? And it really wants DHA. It's, you know, it's, it's essentially that's where all your DHA goes is, is your brain. And, and again, one of the things that, um, is interesting about humans is that we're the only mammal that has fat babies. No other animal has fat babies. And one of the reasons why, um, uh, human babies are fat is because they have adipose tissue as a store of DHA for the brain as it grows.

Dr. Rangan Chatterjee 1:15:26 When you say fat, you don't mean unhealthily fat.

Dr. Tommy Wood 1:15:29 No, I mean, I mean like-

Dr. Rangan Chatterjee 1:15:30 Plump, sort of-

Dr. Tommy Wood 1:15:31 ... healthy, chubby, plump little babies, right? So, if you look at any other mammal, um, when they're born, they're very lean. Even other primates. They don't have large adipose stores. And o- you know, it's, it's an en- So it's an energetic store, right? We know that adipose tissue, fat tissue is a, is a store for energy, but what... But it also stores fats that are then particularly used for the brain, and D- DHA is one of them.

Dr. Rangan Chatterjee 1:15:54 So, a developing brain needs it.

Dr. Tommy Wood 1:15:56 Yes.

Dr. Rangan Chatterjee 1:15:56 Can we therefore say that a developed brain also needs it?

Dr. Tommy Wood 1:16:03 So, this is an exceptionally nuanced topic.

Dr. Rangan Chatterjee 1:16:08 Yeah.

Dr. Tommy Wood 1:16:08 Even more so than any of the other topics that, that we've talked about. A colleague of mine, Dr. Rory Heath, and I wrote a paper recently about DHA and Alzheimer's disease, and some people have said that the DHA in, in patients with Alzheimer's disease, uh, in their brain is low. Others haven't quite found the, the, the same thing. Uh, part of it is probably that, again, your adipose tissue is, is essentially a very nice buffer of DHA that you can use across your lifetime. So it's, it's, it's quite... If somebody is... Unless somebody has never eaten seafood or has never eaten really any long chain omega-3s, it's very unlikely that you're gonna be deficient, um, in... for, for the brain, for cardiovascular function, um, and, and other things. That, that, that may not necessarily be the case. Um, and that's why the omega-3 index or, you know, how, you know, your omega-3s in your blood is a increasingly used, um, risk predictor of cardiovascular disease and things like that.

Dr. Rangan Chatterjee 1:16:58 Mm.

Dr. Tommy Wood 1:16:58 Um, so it's, so it's, it's very nuanced. Um, but if you're going to be maintaining cell membranes and cell function, you're definitely gonna need some. And then the much better line of evidence comes from systemic measures of omega-3. It's impossible for me to measure how much DHA is in your brain, right? But I can measure how much is in your blood.

Dr. Rangan Chatterjee 1:17:18 Right.

Dr. Tommy Wood 1:17:19 And when these studies were done at Oxford, they showed that you needed both adequate B vitamins and enough omega-3s in order for you to get this slowing in, in brain atrophy and cognitive decline. So, if you measure omega-3 levels in people and they're low, they have a, a faster rate of cognitive decline, which tells me that that's important.

Dr. Rangan Chatterjee 1:17:41 Yeah.

Dr. Tommy Wood 1:17:41 Because if you fix it, then you can, you can change that.

Dr. Rangan Chatterjee 1:17:44 Yeah, it's super nuanced.

Dr. Tommy Wood 1:17:47 [laughs]

Dr. Rangan Chatterjee 1:17:48 Um, but it's super important because, you know, Tommy, one of the things that I've noticed is I have seen patients thrive on radically different diets.

Dr. Tommy Wood 1:18:01 Yeah.

Dr. Rangan Chatterjee 1:18:01 So, I'm like, there is no one true human diet that's for everyone, in my view.

Dr. Tommy Wood 1:18:06 Yeah.

Dr. Rangan Chatterjee 1:18:06 It's just based upon 21 years now of clinical experience, it's like I, I, I, I've seen nothing to back that up. There are some principles, whole foods, uh, as much as you can, minimally processed, you know, decent amounts of healthy fats. There, there are some basic principles, but you can twist it in many different ways, culturally, ethically, you know, taste preference wise, using those principles to seemingly be in good health.

Dr. Tommy Wood 1:18:36 I... So I, I completely agree with, with everything that, that you've said, and I've also seen people thrive on an incredibly wide range of diets. Like I said earlier, I think that's one of the most fascinating things about humans, and we have to take individual health into consideration. And so lots of things are done at the population level that are very important. But if two different individuals can thrive on very different diets, and it supports their health in objective ways, and they feel good, we have to be able to support them.

Dr. Rangan Chatterjee 1:19:04 [laughs]

Dr. Tommy Wood 1:19:04 And, and, and i- in doing that, um... And to go back to omega-3s, like I don't... If you don't wanna eat seafood, there are algal, um, sources of long chain omega-3s, right? So, you can do plant-based versions. Absolutely.

Dr. Rangan Chatterjee 1:19:17 And you would recommend that to people?

Dr. Tommy Wood 1:19:19 Um, I would recommend... So, I don't want to show up and just say people should take all these supplements. Ideally, you'd test, right? It's not difficult. I mean, an idea... You know, in, in my perfect world, you would have access to this test through your doctor. It shouldn't be something you have to pay for, uh, because- ... is much cheaper than you getting a whole bunch of cardiovascular and cognitive diseases because you just didn't know that what you needed was a bit more omega-3. Which-

Dr. Rangan Chatterjee 1:19:46 So you would just ... You would, you would do one of those what? Blood spot tests?

Dr. Tommy Wood 1:19:49 Yes.

Dr. Rangan Chatterjee 1:19:49 That omega-3 test.

Dr. Tommy Wood 1:19:49 You do a blood spot for an omega-3 index. Um, and if you're in a good range, then don't worry about it. Um, if-

Dr. Rangan Chatterjee 1:19:55 So that's the ... I think that's really empowering. It's like, look, if you're choosing to eat predominantly plants, you're choosing not to eat animal products, and you're maybe thinking about what Tommy just said and other guests have said in the past, thinking, "Okay, well, why don't I just go and measure my levels?"

Dr. Tommy Wood 1:20:11 Yeah.

Dr. Rangan Chatterjee 1:20:11 That seems like a pretty practical approach to take.

Dr. Tommy Wood 1:20:14 Yeah. And there are, there are some studies that have been done that have looked at the omega-3 levels, the DHA levels of, um, uh, omnivores versus vegans. And sometimes vegans have lower levels, but there have been studies that showed no difference, right? So you can eat a plant-based diet and maybe you don't have any issues whatsoever. One, one thing that's interesting is that there may ... You know, I don't at this point believe in nutrigenomics where you can measure your ... You can, uh, you know, get a genetic test that will tell you the foods that you should eat. I don't think that we're at a point where we can do that. But one of the things that we know the most about is how our body metabolizes specific types of fats. Um, and there have been, there have been some studies that showed that if your ancestors became agriculturalists longer ago, right? So they were usually closer to the equator, usually became farmers, um, further away in the ... in your ... in our ancestral history, like more thousands of years ago, then the body has adapted to being able to take shorter omega-3s like, um, ALA which you can find in nuts and seeds and some grains, and then turning into these longer chain ones.

Dr. Rangan Chatterjee 1:21:23 Mm.

Dr. Tommy Wood 1:21:24 By comparison, um, say half ... You know, half of my family is from Iceland, right? You can't grow grains in Iceland. Um, there's not a starchy carbohydrate to be seen anywhere, right? They ate seafood and they still do, and you know, that was where they got their omega-3. So their bodies never had to adapt to it.

Dr. Rangan Chatterjee 1:21:42 Yeah.

Dr. Tommy Wood 1:21:43 So there may be some people, and one of the reasons why they thrive on a completely, uh, p- plant-based diet is because they're really good at converting some of these precursors to the longer-

Dr. Rangan Chatterjee 1:21:53 Yeah

Dr. Tommy Wood 1:21:53 ... chain, uh, omega-3s, and that's partly based on their ancestry and some other genetic components. So that's why I don't think that everybody who eats a plant-based diet should take an omega-3 supplement. I think they should test, and then if they need to change something, they should, but if they don't, then great.

Dr. Rangan Chatterjee 1:22:07 Yeah. Something potentially so simple has become so complicated 'cause for years we would've just had our nutrition dictated by geography, climate, by culture, what our parents and grandparents fed us. You know what was really interesting, Tommy? I went to Greece this summer and we were on this island called Ithaka, beautiful island. We'd, we'd been in Greece for about 10 days at this point, and you know, we'd been enjoying chill-out time, my wife, myself, the family. We'd been enjoying Greek foods. Um, but most of the vegetables we were getting served were aubergines and tomatoes.

Dr. Tommy Wood 1:22:50 Yeah.

Dr. Rangan Chatterjee 1:22:51 Like literally every day. And we were at this restaurant in Ithaka, and I remember, um, I think the kids fancied something different.

Dr. Tommy Wood 1:22:59 Uh-huh.

Dr. Rangan Chatterjee 1:22:59 And I said to the ... I think she owned the restaurant. She was serving us. I said, "Hey, um, you know, do you have any like other vegetables at all, like I don't know, broccoli or something else?" [laughs] And I learnt so much, Tommy, 'cause she just looked at me baffled and-

Dr. Tommy Wood 1:23:14 [laughs]

Dr. Rangan Chatterjee 1:23:15 ... she just said, "No, they're not in season."

Dr. Tommy Wood 1:23:18 Yeah.

Dr. Rangan Chatterjee 1:23:20 And I thought, isn't that interesting? It, it ... She couldn't even fathom what, what ... You, you wanna eat something that's not in season. Like it didn't compute. And it was really lovely actually.

Dr. Tommy Wood 1:23:30 [laughs]

Dr. Rangan Chatterjee 1:23:30 It really made me think about how by having access to different foods three times a day and seven days a week we can eat something different. We've ... I don't know. It w- ... It was ... I don't know. Any comments on that at all?

Dr. Tommy Wood 1:23:41 I think more broadly it's very possible that in the future we'll figure out the perfect human diet. We can engineer it down to like the micronutrient and the exact level that each individual needs.

Dr. Rangan Chatterjee 1:23:54 For each ... You mean the personalized diet-

Dr. Tommy Wood 1:23:56 Yeah

Dr. Rangan Chatterjee 1:23:56 ... for each person?

Dr. Tommy Wood 1:23:56 Like I'm su- At some point in the future that may be possible.

Dr. Rangan Chatterjee 1:23:59 Yeah.

Dr. Tommy Wood 1:23:59 But right now it isn't. And so where I think we should get a lot of, a lot of our information around our diet are those things like what's seasonal, what was available to us, you know, in recent history. Um, and then yes, I think you should also take advantage of modern medicine and test the things that you should test. And there are objective measures that we can take, uh, for our health from blood tests or, you know, if people are ... Or you know, colonoscopies and all these, right? There are these things that we can take advantage of. If your diet is supporting your health and/or there are ... It's ... You know, you f- you feel great and, and everything is going well, I see no reason to change it. Um-

Dr. Rangan Chatterjee 1:24:46 Yeah

Dr. Tommy Wood 1:24:46 ... and like that ... I think that's what's really critical.

Dr. Rangan Chatterjee 1:24:49 Yeah. Why would anyone change their diet when they're thriving?

Dr. Tommy Wood 1:24:52 Yeah.

Dr. Rangan Chatterjee 1:24:53 Like-

Dr. Tommy Wood 1:24:53 Whatever it is.

Dr. Rangan Chatterjee 1:24:54 Whatever it is.

Dr. Tommy Wood 1:24:54 Whatever it is.

Dr. Rangan Chatterjee 1:24:55 Yeah. W- And, and one of the hidden, one of the unintended consequences, like I wanna talk about gut health with you 'cause you, you published a, a, a ... I read it today. It's a brilliant, brilliant paper. Um, I think it was in 2021 that you published it.

Dr. Tommy Wood 1:25:09 Yeah, I think that last year. Yeah, yeah.

Dr. Rangan Chatterjee 1:25:10 One of the other things I've been reflecting on over the summer is gut health. We didn't know about this organ really on, on a, on a big scale maybe 10 years, maybe 15 years ago. It's not ... It's pretty new. What are we missing? A- and in particular, Tommy, you mentioned some of your friends who are eating maybe what might be termed a carnivore diet these days-

Dr. Tommy Wood 1:25:35 Yeah

Dr. Rangan Chatterjee 1:25:35 ... and are seemingly thriving. And I had Tim Spector on in July. And I mentioned to Tim, 'cause Tim was talking about gut health and talking about 30 plant foods a week, and I mentioned ... And I've got patients like this, I've got friends like this. One particular friend of mine who I spoke to Tim about, I said, "Tim, but I've got a friend who has tried everything. She used to be paleo, she was vegan, she was raw food. She's very educated on health. She's a practitioner. And about five years ago, she pretty much moved to close to carnivore. And I don't know many people ... She's in her 50s. She is thriving. She looks great. She can run ultramarathons. Um, I've done stuff with her. I've seen her work. She can work for 14 hours straight. Cognitive function completely just as good at 9:00 PM as it was at 7:00 AM. It's phenomenal to see. But I'm thinking if we take a step back for a minute, there are so many reports of people thriving on these animal heavy diets, autoimmune symptoms going, joint pain going. Like, we can either put our head in the sand as a profession and go, "No, you've got to do this. You've got to eat more fiber," or go, "Wait a minute. Well, what's going on here? Why are s- people not following the dietary advice and are thriving?" And she's also done all her blood tests. Her triglyceride to HDL ratio is fantastic. Her HbA1c is amazing. What's your perspective, Tommy?

Dr. Tommy Wood 1:27:10 So I completely ... You know, o- o- on the gut front, and again, I, I know people who are much smarter, and know much more about this than, than I do, so I've, I've learned a lot from them. One of them is, uh, Dr. Lucy Manning, who I wrote this, this paper with. Um, and I think the gut has really been this thing where the more we know, the more we realize we don't know. Um, and again, the, the, the paper we wrote tried to come at this from, like, a, a first principles idea, which is that ... So if we think about the wide variety of, of environments and diets that humans thrived in and thrived on, how common is it, how common would it have been for you to have 30 different plant foods in your diet in a week, right? You're in Greece. Two things are in season, tomatoes and aubergines. You talked about that, right? What are the other 28 that you're supposed to find in the environment? Like, it's just not something that our guts ever, you know, are used, quote-unquote, "used to seeing." That doesn't mean it's bad, right? I'm not saying that it's bad.

Dr. Rangan Chatterjee 1:28:18 Yeah.

Dr. Tommy Wood 1:28:19 I'm just saying, like, what are the things that, you know, our guts have helped us through in the past? And if you think about it that way, then you have to think about scenarios when, like, there were no plants, right? So, so, you know, we've come at it from this idea that, uh, for the gut, plants are essential, fiber is es- fiber is essential, and that's pretty much because in large population studies, um, we've told people that that's the case. So people who are more health conscious do that, but they also don't smoke, and they sleep more, and they exercise more, right? The healthy user bias. Um, and if we think about our guts and, you know, the rest of the body is the same, but in a healthy individual, it's, it's adaptable to many different types of fuel, right? Um, is it blood glucose, or is it fat, or is it ketones, right? These dif- these different, um, sources of energy that you can use, that you need to run your heart or your muscles or your brain. Your gut is the same. And the traditional story is that you need fiber, that your gut bugs turn to something we call short chain fatty acids like butyrate. That provides the fuel for your, um, enterocytes, the cells in your gut. But what you see quite clearly is that your gut can use a wide range of fuels. So yes, it can use those. If, uh, if you eat predominantly plant foods, you'll make short term fatty acids like butyrate. That will, that will be the source of fuel. But if you eat more protein, then you'll make what we call iso short chain fatty acids, and those essentially have the same function. So you can support your gut health just fine with the metabolites from meat rather than plants. The gut, the gut cells will still use it. Uh, you can also use acylcarnitines, which are metabolites of fats. Um, or if you're on a ketogenic diet, the, the ... It doesn't come from inside the gut like those other things do from the gut bugs. It can come from the blood. So you can take ... The, the cells in the gut can take ketones from the blood. If you're fasting or, um, you know, fasted because there's no food available, right? If there's no food available, your gut still has to be able to survive. It can't just, like, give up and stop working.

Dr. Rangan Chatterjee 1:30:26 Mm.

Dr. Tommy Wood 1:30:26 Right? Because as soon as you get food, it needs to function. So then if you, for whatever reason, don't have access to food, your body makes a bunch of ketone bodies, and the gut can use those for energy as well. So the gut is incredibly metabolically flexible based on the systemic health of the body and physiology of the body. So what I think we've seen in a lot of studies around the gut is that something that affects systemic physiology affects the gut, and then that affects the types of microbes that get selected for within the gut. So-

Dr. Rangan Chatterjee 1:31:01 Let's, let's just back up. Systemic physiology, what ... how would you say that in layman's terms?

Dr. Tommy Wood 1:31:04 Yeah. So, so basically your general health, right? In other parts of the body.

Dr. Rangan Chatterjee 1:31:07 So, so you do something that's affecting your general overall health.

Dr. Tommy Wood 1:31:10 Yes.

Dr. Rangan Chatterjee 1:31:11 That's then affecting the health of your guts.

Dr. Tommy Wood 1:31:13 Yes.

Dr. Rangan Chatterjee 1:31:14 And then you're measuring bugs in there, and we're make- we're drawing conclusions from that.

Dr. Tommy Wood 1:31:20 Exactly. And it's, uh ... It goes in both ways. So we know that the bugs in your gut can affect your body, but it really seems like what's happening in your body elsewhere, and that can happen with changes in sleep or diet or physical activity, right? So when you exercise, that affects your general health. It affects what happens in your heart and your blood vessels and your muscles. They, you know, secrete a bunch of, um, chemicals and hormones and things like that. That can af- that affects your health, it also affects your gut. And then what happens is your gut ch- is affected by that, by just by your health changing. That then changes the kind of bugs that survive in that gut. So you'll see things change within the gut, right? You'll see different bugs, but it's because of what's happening elsewhere in the body.

Dr. Rangan Chatterjee 1:32:09 Hmm.

Dr. Tommy Wood 1:32:10 So I think we've ascribed too much to the bugs that we measure, and it's also the bugs we can measure.

Dr. Rangan Chatterjee 1:32:17 Yeah.

Dr. Tommy Wood 1:32:18 There's a whole bunch of stuff that we're just not able to measure, and this has been another problem with, um, studying the gut microbiome, is that historically we've used, um, a, a cheaper measure called, um, looking at something called 16S RNA. Um, and when I've talked about this, um, previously, it, the level of information it gives you is it's like if you think about the lineage of dogs, right? There are animals, and then canines, and then the, the sort of the, the house dog.

Dr. Rangan Chatterjee 1:32:48 Hmm.

Dr. Tommy Wood 1:32:48 The dog that we have, dogs that we have at home. So a 16S RNA can tell you this is a dog rather than a cat, but it can't tell you whether it's a French d- bulldog or a Doberman, right? Which are vastly different dogs.

Dr. Rangan Chatterjee 1:33:01 Hmm.

Dr. Tommy Wood 1:33:01 And it's the same thing with gut bugs. So it might tell you, yes, I think I have an idea what this bug is, but it tells you nothing about its specific functions. Um, and a lot more about what's happening in the gut is based on the function of the bug rather than what the bug is.

Dr. Rangan Chatterjee 1:33:15 Yeah.

Dr. Tommy Wood 1:33:15 And so vastly different bugs can have the same function, but you might just focus on one that has a specific function and think we need this, when actually something else entirely could take that function. So it's ... D- the information that we have is incomplete. Um, I think we've ascribed too much, um, you know, too much to its-

Dr. Rangan Chatterjee 1:33:34 Yeah

Dr. Tommy Wood 1:33:34 ... to its activity. Doesn't mean it's not important. I think it's very important.

Dr. Rangan Chatterjee 1:33:37 No, for sure.

Dr. Tommy Wood 1:33:38 But I, I think we've given it too much credit and, and taken away what's maybe happening elsewhere in the body at the same time.

Dr. Rangan Chatterjee 1:33:44 And also, maybe it's not even giving it too much credit, but it could also be, you know, we're overly focusing on lifestyle change influencing the gut microbiome, influencing our overall health. Maybe it's just the [laughs] lifestyle change is influencing our overall health, as you say, which is then influencing the gut microbiome.

Dr. Tommy Wood 1:34:06 Exactly. Exactly.

Dr. Rangan Chatterjee 1:34:06 And this is one of the key things I think I've evolved my view on, uh, over the past few years, is this maxim that we need fiber for optimal health. I, I, I don't know the answer to that. I've just ... I'm very open-minded, and I, I just ... I can't, um, make that work in my head cognitively, and also see many, many people thriving, literally thriving in every way that I can see on low fiber diets.

Dr. Tommy Wood 1:34:49 Yeah.

Dr. Rangan Chatterjee 1:34:49 I think it doesn't add up. Like, we've gotta do better.

Dr. Tommy Wood 1:34:52 [laughs]

Dr. Rangan Chatterjee 1:34:53 Like, there's, there's ... Do you know what I mean?

Dr. Tommy Wood 1:34:54 Yeah. And, and, and again, um, I think when we, when we've looked at ... So I'm, I'm not gonna say that fiber isn't important, because I think in, in the, in the setting of the, the modern mixed diet where most foods are ultra-processed, and we think about the things that we talked about earlier that may be able to, you know, help support gut function, you're probably not getting any of those, and in that setting, fiber may be beneficial.

Dr. Rangan Chatterjee 1:35:22 Hmm.

Dr. Tommy Wood 1:35:23 It's also, uh, fiber in the diet when we ask people about their diet. It's like a marker of a bunch of other things.

Dr. Rangan Chatterjee 1:35:29 Yeah.

Dr. Tommy Wood 1:35:29 Like, usually if you're eating more fiber, you're eating higher quality foods. Um, and fiber may affect things like satiety, right? So if you're eating more fiber, then maybe you eat total fewer calories in an environment-

Dr. Rangan Chatterjee 1:35:40 Yeah

Dr. Tommy Wood 1:35:40 ... that encourages us to eat more calories than we need. So there are these signals that maybe it's beneficial, but that doesn't mean that it's essential.

Dr. Rangan Chatterjee 1:35:47 Yeah. And, and just to, just to clarify my own view, I'm also not saying fiber is not important.

Dr. Tommy Wood 1:35:52 Yeah.

Dr. Rangan Chatterjee 1:35:52 There is plenty of research which is suggesting that more fiber is associated with better health outcomes. I've written about this before, right? So I'm, I'm just ... I think we always need to remain open-minded.

Dr. Tommy Wood 1:36:03 Yeah.

Dr. Rangan Chatterjee 1:36:03 And go, just 'cause we believe this to be true, just because everyone said it was true, maybe it's a partial truth.

Dr. Tommy Wood 1:36:10 Yeah.

Dr. Rangan Chatterjee 1:36:11 Maybe, maybe it's true for a lot of people. And also the other thing I think with diet, Tommy, is that when we look at these ancestral populations, these hunter-gatherer tribes, and we look at what they're eating and, you know, the Hadza tribe in Tanzania are reported to eat a ton of fiber, maybe 100, 150 grams a day. I've seen in some reports compared to, you know, an urban population, a Western population that may be struggling to get 15, 20, 25 grams a day, right? So I get that on the face of it, it seems like a huge difference, and hey, we want their health outcome, so let's do that. Let's increase the fiber. But it also depends, doesn't it? That diet on top of what?

Dr. Tommy Wood 1:36:57 Yeah.

Dr. Rangan Chatterjee 1:36:58 So if you've grown up there with low stress, eating naturally in sync with the seasons, you know, without the, the urban Western societal pressures that, you know, affect all aspects of our physiology, well, maybe that diet works really well. But maybe, maybe in the, you know, the world in which we, we live, you live in America now, I live in the UK, but so many people have got poor metabolic health already. They're already, um, got suboptimal health, so maybe they need a corrective diet.

Dr. Tommy Wood 1:37:33 [laughs]

Dr. Rangan Chatterjee 1:37:34 Do you know what I mean?

Dr. Tommy Wood 1:37:34 Yeah.

Dr. Rangan Chatterjee 1:37:34 It's kind of like ... And I, I sort of hypothesized in my first book why a low carb diet seems to work so well for so many people in the Western environment. Might be because we're overly stressed, we're underslept, we're, uh, undermoved, we're ... We've had too many calories or the wrong types of calories. We, we are insulin resistant, and therefore maybe in that setting there's a There's a kind of unique role for it.

Dr. Tommy Wood 1:38:01 Yeah

Dr. Rangan Chatterjee 1:38:01 I, I don't know. I mean, it ... I'm not saying I've got the answers, or, um, I don't think you are saying you've got the answers either. But it's worthy of discussion.

Dr. Tommy Wood 1:38:09 Yeah. Um, in, in my mind, uh, there's this ... You know, every- every- everything that we use to describe human health, everything we use in biology is some kind of model, right? Um, and because we can't ... We c- we're unable to completely explain everything, right?

Dr. Rangan Chatterjee 1:38:27 [laughs]

Dr. Tommy Wood 1:38:27 It's not physics, and even in physics they can't do that. Um, but there's this fam- uh, George Box is a statistician, has this famous quote, which is called ... Which says, "All models are wrong, but some models are useful."

Dr. Rangan Chatterjee 1:38:38 [laughs]

Dr. Tommy Wood 1:38:39 And I think that's, that's really ... And, uh, I think that's really important to think about, 'cause everything we're th- we're talking about here is some kind of model to, to describe human health. And if your model doesn't allow for the individual that is doing amazingly well eating nothing but beef, then your model is wrong, right? It ... Then it's more wrong than any kind of model you can build that inc- that bui- that, that-

Dr. Rangan Chatterjee 1:39:08 Yeah

Dr. Tommy Wood 1:39:08 ... uh, encompasses that. So I always think, like, the outliers are important because they force you to change the parameters-

Dr. Rangan Chatterjee 1:39:15 Yeah

Dr. Tommy Wood 1:39:15 ... of your model. And if you don't, I think that's incredibly unscientific. So yes, you can say, "That's interesting. I wanna learn more about that," but at some point you then have to try and incorporate it into whatever model it is that you're building that says, you know, well, why is it that we're seeing these ... You know, if humans can thrive in a scenario where they're not eating any fiber, then that has to be incorporated into the model somehow.

Dr. Rangan Chatterjee 1:39:37 Yeah. Yeah, I love that. I love that. Muscles, right? We've, we've drawn an analogy, you've drawn an analogy early on about muscle health and brain health.

Dr. Tommy Wood 1:39:46 Yeah.

Dr. Rangan Chatterjee 1:39:48 And I'm really interested as to practically what advice would you give to people who wanna optimize their brain health in terms of, yes, physical activity, but, but I guess specifically I'm interested in, in muscle. Um, I know, you know, you lecture on this. You, you're gonna give a talk I think this weekend-

Dr. Tommy Wood 1:40:12 Yeah

Dr. Rangan Chatterjee 1:40:12 ... on, on muscle mass and longevity-

Dr. Tommy Wood 1:40:13 Uh-huh

Dr. Rangan Chatterjee 1:40:13 ... in the UK, which you'll hear. We had Dr. Gabrielle Lyon on recently. She was talking, um, about protein intake, uh, the importance of resistance training. I would love your perspective on these things.

Dr. Tommy Wood 1:40:29 So I obviously haven't heard your interview with, uh, with, uh, Dr. Gabrielle, but I imagine that I will have agreed with pretty much everything she said. So you can hear what I say, and then you can ... Because in general, I, I, I think she's, she's, she's fabulous, and she f- she focuses on, on really important things, which is muscle tissue and protein intake. Um, and the re- I, I mean, there are multiple reasons why muscles are important. They're our biggest glucose sink. So we talk about blood sugar, you talk about, you know, that being important for diabetes risk, but also cardiovascular disease risk, uh, dementia risk. 75% of your blood sugar is taken up into your muscles, and the more muscle you have and the more you move it, the more glucose blood sugar that they take up. So if you're trying to regulate your blood sugar, which is relevant to the vast majority of, of adults, 'cause they probably ... You know, again, the average individual at least has pre-diabetes, average adult in, in the US and the UK, and, and similar studies have been shown, shown that in Europe.

Dr. Rangan Chatterjee 1:41:26 That's pretty alarming.

Dr. Tommy Wood 1:41:27 Yeah. And so, so I think the, the projected number in the US is 60%, um, have at least pre-diabetes, or obviously if you progress then that includes pre-diabetes and frank type 2 diabetes. 60% of US adults.

Dr. Rangan Chatterjee 1:41:41 Currently, or-

Dr. Tommy Wood 1:41:42 Currently

Dr. Rangan Chatterjee 1:41:42 ... and do you know what that figure is in the UK?

Dr. Tommy Wood 1:41:44 Um, I believe it's 40 or 50%.

Dr. Rangan Chatterjee 1:41:49 Yeah.

Dr. Tommy Wood 1:41:50 So muscles are your most important glucose sink if you wa- Right, if you wanna regulate your blood sugar, you need to create somewhere for that blood sugar to go, right? Um, and muscles are the thing. Uh, 75% of blood sugar goes up into, into your muscles.

Dr. Rangan Chatterjee 1:42:04 So the more muscle you have-

Dr. Tommy Wood 1:42:06 Yes

Dr. Rangan Chatterjee 1:42:06 ... the easier it is to regulate your blood sugar.

Dr. Tommy Wood 1:42:09 Absolutely. And the more you move it, so ... And so both are important, right? So the total mass, and then how much movement you ha- the, the, the amount that you move it. Um, and there are, there are several studies that have shown that. But you can, in, you know ... Again, in type 2 diabetics you can put on continuous blood sugar monitors or look at their, you know, blood sugar, and the more they move, the better their blood sugar is controlled. Um, and if you have more muscle and you move it more, you can control that even better. So that's one reason why muscle is important. It's also, um ... It's a, it's an organ. Like, it secretes factors and hormones and things that we're still learning about, right? Um, every month there's a, another paper in a fancy journal that says, "We just learned this thing that happens when you exercise, and it makes this molecule, and then we inject that molecule into mice and they live longer."

Dr. Rangan Chatterjee 1:42:59 That speaks to what you just said about the gut, right?

Dr. Tommy Wood 1:43:00 Yeah.

Dr. Rangan Chatterjee 1:43:00 How long have we been studying muscles compared to how long have we been studying the gut? Years.

Dr. Tommy Wood 1:43:06 Yeah, decades.

Dr. Rangan Chatterjee 1:43:06 Decades on muscles, and we're still learning new stuff that we're like-

Dr. Tommy Wood 1:43:08 Yeah

Dr. Rangan Chatterjee 1:43:08 ... "Oh, we didn't realize."

Dr. Tommy Wood 1:43:09 Yeah.

Dr. Rangan Chatterjee 1:43:10 So it's kind of naive on the gut, isn't it?

Dr. Tommy Wood 1:43:12 [laughs]

Dr. Rangan Chatterjee 1:43:12 To think after 10 years of study we kind of know all this stuff.

Dr. Tommy Wood 1:43:15 Yeah, e- exactly. And so one of the reasons why I like to use exercise as an example is because everybody rec- ... Right, diet we can argue about. Some other things we can argue about. Nobody argues about physical activity, right?

Dr. Rangan Chatterjee 1:43:27 Yeah.

Dr. Tommy Wood 1:43:27 Everybody recommends it. Every health body, every governmental org- organization, every non-governmental organization says, "You should, you should move more," right? Physical activity is good for your health. But we don't know how it works yet. I mean, we know lots of things, but we don't know all the things that happens when, happens when you exercise. And so what ... You know, it's a ... Um, when you, when you exercise, you release a whole bunch of factors that sup- you know, directly support the brain, things like brain-derived neurotrophic factor. You secrete things that decrease systemic inflammation. Um, a whole wide range of things. So it's this ... It's a secretory organ occ- you know, just like, um, just like the, the, the pancreas or the thyroid Um, b- but, uh, when you move it. Um, and then sort of more practically, as you get older, we, we know that you lose muscle mass as, as you age, and it particularly starts to decline from about 60, muscle, muscle mass. So it starts slowly in your 30s, and then it really accelerates when you hit about 60 on average. But strength declines pretty much continuously from your 30s. So you lose strength more th- y- more f- more quickly than you lose muscle tissue. And strength is really the thing, like functional, um, functional capacity of muscle is, is, is really important. It's like saying you don't want a bigger brain, you want a brain that works better, right?

Dr. Rangan Chatterjee 1:44:44 Mm-hmm.

Dr. Tommy Wood 1:44:44 Like that's ... That the function is the important thing, and, uh, strength is a really important predictor of mortality and, uh, cognitive decline. A- and there are simple things like if you have enough muscle mass and enough strength, then you're not gonna fall over, you ... And break a hip. And, right, if you get into your s- if you get into your 70s or 80s, you fall and break a hip, you have a very high chance of dying-

Dr. Rangan Chatterjee 1:45:07 Mm-hmm

Dr. Tommy Wood 1:45:07 ... within the next, well, even days, but then also weeks and months afterwards. So, like your muscle tissue supports pretty much, you know, all the ... all, all these important ... Like, it supports every other organ in the body. Um, and what's int- interesting to me about exercise, particularly when you think about lon- lo- longevity and aging, um, there was a, uh ... About 10 years ago, there was a paper that came out called the Hallmarks of Aging, which are all these things that you can measure biochemically in cells that happen as the, as the body or the cell ages. Physical activity and exercise is the only thing that reverses all of those components, right? It's the only thing that can actively anti-age you in everything that happens as you age. Um, so it, it, it basically, uh, affects everything. And then I know it's important to give practical advice, right? How, how ... Well, like what's ... How much is enough? And, um, you know, whenever I talk about muscles, I have to, you know, m- I have a phil- philosophical conflict, which is like I really like lifting weights, right?

Dr. Rangan Chatterjee 1:46:12 [laughs]

Dr. Tommy Wood 1:46:13 So everybody ... You know, the first thing that happens when I talk about muscle mass is people are like, "Well, I don't wanna look like, don't wanna look like you."

Dr. Rangan Chatterjee 1:46:19 [laughs]

Dr. Tommy Wood 1:46:20 And like that's fine. That's great. You don't have to. Um, and you basically just have to be in the top 50% of the population, right? So if you go out and you find 10 people like you, if you have ... If you're in the top half in terms of the amount of muscle mass, then you're good. That's enough.

Dr. Rangan Chatterjee 1:46:37 So that, that's the challenge to the listeners at the moment, right?

Dr. Tommy Wood 1:46:39 That's the challenge.

Dr. Rangan Chatterjee 1:46:39 Find 10 people who are like you-

Dr. Tommy Wood 1:46:41 Yeah

Dr. Rangan Chatterjee 1:46:41 ... and have a press-up competition.

Dr. Tommy Wood 1:46:42 Yeah, exactly.

Dr. Rangan Chatterjee 1:46:43 [laughs]

Dr. Tommy Wood 1:46:43 And if you're s- if you're, if you're in the top half in terms of the number of press-ups you can do, then you're fine. Um, you don't have to do that. But so what does it take to achieve that kind of, um, some- something like that? And it's, it's really not very much. Um, if, if you've never done any kind of resistance training, and, um, resistance training, I mean, uh, it could just be, uh, body weight stuff. So some of the things from your books, uh, like your kitchen workout. Uh, it can ... You can use bands. Yes, you can use weights and go to the gym, but you don't need to. Um, uh, this morning I w- I watched a talk by Professor Sir Muir Gray, um, who, who was talking about, um, the healthiest thing to do with, uh, bags of sugar is to use them as weights.

Dr. Rangan Chatterjee 1:47:24 [laughs]

Dr. Tommy Wood 1:47:24 And I was like, great. Yeah, you could ... So you could use bags of sugar. You could use, like, cans of beans, um, that provides resistance. And if you do, um, two to three sets per muscle group, right? So maybe you have to do bicep curls and squats and a press to, like, cover all your, your, your, your muscle groups. Two to three sets per week is probably enough.

Dr. Rangan Chatterjee 1:47:46 Two to three sets per week?

Dr. Tommy Wood 1:47:47 Per week. So the minimum effective dose to m- to increase strength is somewhere between two and four sets per muscle group per week.

Dr. Rangan Chatterjee 1:47:56 And when you say sets, is that 10? W- Bicep curls, is that 5?

Dr. Tommy Wood 1:48:00 Yeah.

Dr. Rangan Chatterjee 1:48:00 Is it 15? What ... How do we define a set?

Dr. Tommy Wood 1:48:02 So that's a great question, and the ... Again, what's really great is the answer is it, it doesn't matter-

Dr. Rangan Chatterjee 1:48:10 [laughs]

Dr. Tommy Wood 1:48:11 ... as long as you go to something approaching what we call voluntary muscular failure, which is basically, this is really hard. I can't do it anymore, right? So if you pick ... If, if whatever you're doing, you can do five, and you're like, "I can't do six," then that's enough.

Dr. Rangan Chatterjee 1:48:28 Mm-hmm.

Dr. Tommy Wood 1:48:28 But if whatever you're doing, you can do 30, but you can't do 31, then that's enough.

Dr. Rangan Chatterjee 1:48:34 Right.

Dr. Tommy Wood 1:48:34 So it just has to get to a point where it gets hard enough that you say, "I probably can't do any more." Um, and you don't need to, like, really push it and, like, get to the point where you're like, you know, yeah, your form looks terrible 'cause you're sort of, like, trying to muscle this thing up. You don't need to do that.

Dr. Rangan Chatterjee 1:48:48 It's the same principle as doing something new, isn't it? You're just saying maybe 20 to 30 minutes-

Dr. Tommy Wood 1:48:53 Yeah

Dr. Rangan Chatterjee 1:48:53 ... on something that you find challenging, but then it's probably enough after-

Dr. Tommy Wood 1:48:57 Yeah

Dr. Rangan Chatterjee 1:48:57 ... 20 minutes or so.

Dr. Tommy Wood 1:48:58 Yeah.

Dr. Rangan Chatterjee 1:48:59 It's a similar kind of principle with the muscle.

Dr. Tommy Wood 1:49:01 Yeah, exact- And so 20 minutes, two or three times a week, and even if it's just one set each time where in that cho- in whatever you're doing. So say you're doing, uh, some squats, and, and if you can't do squats, then you could just do, like, sit ... You know, getting up and down from a chair, right? If that's the limit. And if you get up and down from a chair 15 times, and you're like, "Oof, I probably couldn't do a 16th," then that's great, that you've done what you need to do.

Dr. Rangan Chatterjee 1:49:24 Yeah, I, I think the important message there is for people ... 'Cause people tend to get hung up on numbers a lot of the time.

Dr. Tommy Wood 1:49:28 Yeah.

Dr. Rangan Chatterjee 1:49:29 Is it 10? Is it 15? Is it five? It's like, no, it's voluntary muscular failure.

Dr. Tommy Wood 1:49:33 Yeah.

Dr. Rangan Chatterjee 1:49:33 So ... And that's gonna change as you get stronger.

Dr. Tommy Wood 1:49:36 Yeah.

Dr. Rangan Chatterjee 1:49:37 Right? So maybe it's you can do f- only two press-ups now, but as you get stronger it'll be, you know, five is what-

Dr. Tommy Wood 1:49:43 Yeah

Dr. Rangan Chatterjee 1:49:44 ... you need to do. And as you get stronger, it's gonna be 10.

Dr. Tommy Wood 1:49:45 Yeah.

Dr. Rangan Chatterjee 1:49:46 Yeah. So that's the minimum effective dose.

Dr. Tommy Wood 1:49:50 Yeah.

Dr. Rangan Chatterjee 1:49:50 Okay? So the premise is we're trying to maintain our brain health as we get older. Uh, above the age of 30, we start to lose muscle mass. You're making the case that lean muscle mass is very important for our cognitive health and many other aspects of our health.

Dr. Tommy Wood 1:50:05 Yeah, yeah.

Dr. Rangan Chatterjee 1:50:06 So you're saying the minimum effective dose is two to three sets on most muscle groups. ... a week. So that's gonna do something, that you're gonna get benefit from that.

Dr. Tommy Wood 1:50:16 Yeah.

Dr. Rangan Chatterjee 1:50:18 You've given us the minimum effective dose, but presumably more, up to a point I guess, can be better?

Dr. Tommy Wood 1:50:26 Yes. And so what I think is the ba- like the best balance of, like the amount of response you get versus what's practical for most people, is probably something more like eight to 12 sets per muscle group per week, split over two to three sessions. And so it's very common in the exercise literature to see three times per week, three sets per muscle group, and then, you know, they usually do like something like eight to 12 reps-

Dr. Rangan Chatterjee 1:50:59 Yeah

Dr. Tommy Wood 1:50:59 ... and, and, and, uh, change the weight to, to get it so that by, you know, 10 or 11 you're at that point of failure. Like, whatever that is for you.

Dr. Rangan Chatterjee 1:51:06 Yeah.

Dr. Tommy Wood 1:51:08 So that's... And that's very common. And so there was, um, they've, they've done studies where they've compared individuals in their 70s versus individuals in their 20s, and with that kind of training protocol, so three times a week, three sets per muscle group maybe, so maybe six to eight different exercises each time, even individuals in their 70s, you know, are gaining significant muscle mass, significant strength, right? So again, it's, it's not this thing you can't do it, right? The body still responds, it still adapts. Once you've achieved whatever level you want to achieve, you need much less to maintain it, right? You can maintain it with those levels we were talking about before, two or three times per week.

Dr. Rangan Chatterjee 1:51:44 Mm.

Dr. Tommy Wood 1:51:44 Uh, whatever you've built up. Um, so that's important, too, right? Maybe you get to a certain point and you're like, "Well, I only just want to maintain my strength." You need much less to maintain that you need-

Dr. Rangan Chatterjee 1:51:53 Mm

Dr. Tommy Wood 1:51:53 ... than you need to actively build, so that's important, too. Um, there's a, there was a very nice study, uh, called the SMART, the SMART trial, where they did... gave people either resistance training or cognitive training or both, and they looked at sort of function and, and, um, and things, uh, like structure of the brain. They were looking particularly at the brain. And these, again, individuals in their 70s, and the resistance training protocol, which significantly improved function and structure in some areas of the brain, 'cause we were talking about the brain, was just that. It was three times per week, uh, three sets of six different machines in the gym. So you could go to your local, you know, local gym, you just do like some kind of row, some kind of press, a leg press, right? Five or six different machines, three times a week, three sets of eight to 12 for each, and then that showed significant benefits in the brain. Each session was close to half an hour, so it's 90 minutes a week.

Dr. Rangan Chatterjee 1:52:50 Very doable.

Dr. Tommy Wood 1:52:51 Yeah.

Dr. Rangan Chatterjee 1:52:52 And, and, and to really tie in what we were talking about before, Tommy, about access and, you know, making health advice relevant to everyone, uh, maybe people who don't have much disposable income.

Dr. Tommy Wood 1:53:07 Yeah.

Dr. Rangan Chatterjee 1:53:07 Gyms can be expensive.

Dr. Tommy Wood 1:53:09 Oh, yeah.

Dr. Rangan Chatterjee 1:53:09 Right? This doesn't have to be a gym.

Dr. Tommy Wood 1:53:12 No.

Dr. Rangan Chatterjee 1:53:12 You mentioned [laughs] bags of sugar-

Dr. Tommy Wood 1:53:13 Yeah

Dr. Rangan Chatterjee 1:53:13 ... that could be used as weights, tins of beans. You know, many of us have got dumbbells kicking around. You know, in the first lockdown in the UK back in 2020, you could not buy dumbbells or kettlebells anywhere, I think, after a few weeks. Literally everyone had sold out.

Dr. Tommy Wood 1:53:32 Yeah.

Dr. Rangan Chatterjee 1:53:32 So based upon that, this is not science, but based upon that, there are many people-

Dr. Tommy Wood 1:53:38 [laughs]

Dr. Rangan Chatterjee 1:53:38 ... who have got dumbbells or kettlebells kicking around, sitting at home, maybe in a box, maybe in a cupboard, maybe in the garage under some dust. It's not costing any money-

Dr. Tommy Wood 1:53:49 Mm

Dr. Rangan Chatterjee 1:53:49 ... if you already bought it. Huge, huge benefits for your current health, your metabolic health, your brain health. I mean, I know we know this stuff, but when, when you say it out loud sometimes, you go, "Guys, you gotta, you just gotta do it."

Dr. Tommy Wood 1:54:05 [laughs]

Dr. Rangan Chatterjee 1:54:05 You can't just hear the podcast-

Dr. Tommy Wood 1:54:07 Yeah

Dr. Rangan Chatterjee 1:54:07 ... and go, "Oh yeah, I, I know how important muscle mass is." You've got to actually go and do it, but what you're saying is it's not actually that much.

Dr. Tommy Wood 1:54:14 I think that, uh, one of the most important messages that I like to give around exercise is that literally anything is beneficial. Like, it's, it's linear. Like, anything more than what you're doing now will have significant benefits for your health. And what we often think, um, and, and we, we may have talked about this in, in the last podcast, was that, you know, if you're gonna go running, right, it has to be an hour, and it has to be hard for it to be doing... And you're just like, "Well, what's the point in going running if I don't have an hour or if I don't-

Dr. Rangan Chatterjee 1:54:48 Yeah

Dr. Tommy Wood 1:54:48 ... get really out of breath?" And that's not true, right? It could be 20 minutes, and it could be a brisk walk, and we know that has significant health benefits. And resistance training is the same. People will think that, you know, what's the point in doing it because, you know, it's only a 4 kilo kettlebell. Like, surely that can't make much difference.

Dr. Rangan Chatterjee 1:55:04 Mm.

Dr. Tommy Wood 1:55:04 It does. It makes a huge-

Dr. Rangan Chatterjee 1:55:06 Yeah

Dr. Tommy Wood 1:55:06 ... difference. Uh, so it doesn't take much. Um, and you can do it with b- so, like, um, I'm traveling for 10 days right now. I won't have access to a gym. I brought two things, a set of resistance bands and blood flow restriction cuffs, which we can talk about more if you want, but basically it makes any exercise that you do much harder with your body weight, and you sort of augment the response to it.

Dr. Rangan Chatterjee 1:55:25 Yeah.

Dr. Tommy Wood 1:55:25 Um, and it weighs, I don't know, maybe a kilo. Could put it in the bottom of my backpack, and I will get great workouts and... Oh, and it maybe costs 20 quid in total, the things that I have in my bag. Um, and that would be enough, right? If I was somebody who was just focused on resistance training for health, I could have those two things and do everything that I needed to do to get almost all the benefit.

Dr. Rangan Chatterjee 1:55:48 Yeah. You know, when I travel, do you know what I take with me?

Dr. Tommy Wood 1:55:53 What?

Dr. Rangan Chatterjee 1:55:53 Skipping rope.

Dr. Tommy Wood 1:55:54 Yeah. Great.

Dr. Rangan Chatterjee 1:55:56 Now, I'm super tall, right?

Dr. Tommy Wood 1:55:57 [laughs]

Dr. Rangan Chatterjee 1:55:57 So I had to get an extra long skipping rope maybe about seven years ago, so I guard it with my life. It's quite hard to get, you know?

Dr. Tommy Wood 1:56:03 Yeah.

Dr. Rangan Chatterjee 1:56:03 People don't realize when you're as tall as a giraffe, it ain't easy to get stuff. But I, I took that on holiday with me this summer. Pretty much done more skipping this summer than I've done in my life. It's phenomenal.

Dr. Tommy Wood 1:56:15 Oh, yeah.

Dr. Rangan Chatterjee 1:56:16 Uh, you know, this whole thing about it not being accessible- That's accessible. What you just said is accessible

Dr. Tommy Wood 1:56:21 Yeah

Dr. Rangan Chatterjee 1:56:22 Um, these, these restrictors, these blood cuff, what were they called again?

Dr. Tommy Wood 1:56:27 Blood flow restriction cuffs.

Dr. Rangan Chatterjee 1:56:27 Blood flow restriction.

Dr. Tommy Wood 1:56:29 Yeah.

Dr. Rangan Chatterjee 1:56:29 I do wanna talk about them, but I think we're gonna have to save that for-

Dr. Tommy Wood 1:56:32 [laughs]

Dr. Rangan Chatterjee 1:56:32 ... uh, conversation number three.

Dr. Tommy Wood 1:56:34 Uh-huh.

Dr. Rangan Chatterjee 1:56:35 Which I hope we can have, 'cause I, I so enjoyed talking to you. Uh, we've tantalized people with, uh, blood tests throughout this conversation. So, some of these blood tests that are, you know, pretty well available for people, um, what blood test do you recommend? What do you think are the most important ones if they're only gonna do a few? And I wonder if you're open to sharing what you think the optimum parameters are, what people should be aiming for.

Dr. Tommy Wood 1:57:09 I've done, uh, like, like I said earlier, a bunch of, uh, work in blood tests, and I've also done a bunch of gut testing, and fancy urine testing and, you know, all these, all these kinds of things.

Dr. Rangan Chatterjee 1:57:19 On yourself?

Dr. Tommy Wood 1:57:20 On myself.

Dr. Rangan Chatterjee 1:57:20 Yeah, me too [laughs] .

Dr. Tommy Wood 1:57:21 On others, on, you know, clients and athletes that I've worked with. And, you know, again and again and again, I just, like, come back to some of the basics that I think can, can be really important. The average adult in the UK probably has at least one or two of the components of metabolic syndrome. And so-

Dr. Rangan Chatterjee 1:57:38 Could you just say we- what metabolic syndrome is?

Dr. Tommy Wood 1:57:41 Yeah, yeah. Yeah, so, so, so if we're talking about, we talk about metabolic health, we talk about insulin resistance, these things that, you know, related to diabetes and cardiovascular disease risk, and Alzheimer, you know, dementia risk. And one of the easiest ways to explain metabolic health, uh, to me, is the absence of metabolic syndrome, which is this, um, syndrome that's, um, increasing in, in prevalence, and it, it basically, the, the more factors you have increase your risk of cardiovascular disease, certain cancers. And it's basically this expression of systemic insulin resistance, so your bo- your body's inability to handle energy properly. That's probably the, the easiest way to do it and or to, to talk about it, and the way we measure that is with a blood sugar test. That's one of the ways we measure insulin resistance. Um, either just a fasting blood sugar in the morning or an HbA1c, which is more of like a, you know, a, a picture of your blood sugar over the last couple of months. And the components of metabolic syndrome are, uh, an increased waist circumference, um, they are low HDL cholesterol, and it's different for men or women, high triglycerides, high blood sugar, and then high blood pressure. So if you were to avoid having any of those things, you're already in such great shape, and those are... That's a really low bar to hit, and those are things that you can get from your GP, um, and you can easily track over time, and they're very cheap. So that's absolutely where I'd start.

Dr. Rangan Chatterjee 1:59:02 Okay, so let's go through some of them.

Dr. Tommy Wood 1:59:03 Yeah.

Dr. Rangan Chatterjee 1:59:04 Uh, fasting glucose?

Dr. Tommy Wood 1:59:07 So fasting glucose, um, the, the criteria for high fasting glucose in metabolic syndrome is the, the presence of pre-diabetes. So, um, there are two ways that you can diagnose that. One is either a fasting blood sugar, um, over 100 milligrams per deciliter, which is 5.6-

Dr. Rangan Chatterjee 1:59:26 Yeah

Dr. Tommy Wood 1:59:26 ... ish millimoles per liter.

Dr. Rangan Chatterjee 1:59:27 Mm-hmm.

Dr. Tommy Wood 1:59:28 Um, or an HbA1c above 5.7%. I can't remember what that is in millimoles per mole.

Dr. Rangan Chatterjee 1:59:32 But you know what's really interesting is that in the US, the pre-diabetic threshold is an A1c of 5.7. In the UK, it's 6.

Dr. Tommy Wood 1:59:40 Oh, interesting.

Dr. Rangan Chatterjee 1:59:41 So we have actually a different arbitrary number-

Dr. Tommy Wood 1:59:44 Yeah

Dr. Rangan Chatterjee 1:59:44 ... when we call it-

Dr. Tommy Wood 1:59:45 Yeah

Dr. Rangan Chatterjee 1:59:46 ... pre-diabetes.

Dr. Tommy Wood 1:59:46 And it is arbitrary. We've, like, had to pick a cutoff point, but of course these things are, you know, on, on a continuum, like everything that we've, we've talked about today.

Dr. Rangan Chatterjee 1:59:52 But, but, so if, if we go on A1c and fasting glucose for a minute because there's normal-

Dr. Tommy Wood 1:59:58 Yeah

Dr. Rangan Chatterjee 1:59:58 ... there's okay, and then there's optimal.

Dr. Tommy Wood 2:00:02 Mm-hmm.

Dr. Rangan Chatterjee 2:00:02 Right? So of course, not being in the abnormal range [laughs] is, is a good start, but many people, I, I would guess many people listening to this show are actually going, "Yeah, okay, but what, what should I be really aiming for?"

Dr. Tommy Wood 2:00:14 Yeah.

Dr. Rangan Chatterjee 2:00:15 So with an HbA1c, again, in kind of old money, um, you know, 6.5 is a diagnosis of type 2 diabetes, 6 in the UK or 5.7 in the US is a diagnosis of pre-diabetes. Where would you ideally like to see people's A1cs? Or can we say that yet?

Dr. Tommy Wood 2:00:35 Um, s- so there are a number of very large population studies that have looked at blood sugar levels, both fasting blood sugar and HbA1c, and then looked at things like mortality-

Dr. Rangan Chatterjee 2:00:46 Yeah

Dr. Tommy Wood 2:00:46 ... which is like a hard endpoint. It's easy to know, like, is this person dead or not? And, and you can then say, "Well, where is the lowest risk of death on, you know, on the glucose scale?" And it seems to be somewhere around fi- you know, maybe 4.5 to just over 5 millimoles of fasting blood sugar, and maybe something similar for HbA1c, like 5 to maybe 5.5 is where the lowest, uh, risk of mortality is at the population level. Um, that's probably because having much lower blood sugar is usually associated with other problems, like alcoholics-

Dr. Rangan Chatterjee 2:01:27 Yeah

Dr. Tommy Wood 2:01:28 ... have lower blood sugar. And it's not the low blood sugar that's, that's the problem, it's the fact that they're, they're alcoholics.

Dr. Rangan Chatterjee 2:01:34 So you're looking after someone, and they've got an A1c, an HbA1c, which everyone listening to this show at the moment probably has access to-

Dr. Tommy Wood 2:01:43 Yeah

Dr. Rangan Chatterjee 2:01:43 ... for either free or very low cost.

Dr. Tommy Wood 2:01:46 Yeah.

Dr. Rangan Chatterjee 2:01:46 Right? So it's something practical that people can actually measure, look at, and then compare it to what we're saying. If someone's got it between then 5 and 5.5, let's say it's 5.5, so only 0.2 away from 5.7-

Dr. Tommy Wood 2:02:00 Yeah

Dr. Rangan Chatterjee 2:02:00 ... right? Are you happy with that? Or do you think lower might be better? Or does it depend on the context of everything else? [laughs]

Dr. Tommy Wood 2:02:09 It absolutely depends on the context of everything else. If your, uh, HbA1c is 5.5, and you d- you know, you have, um... I think waist circumference is tricky. Um, I like waist-to-height ratio.

Dr. Rangan Chatterjee 2:02:21 Yeah, me too.

Dr. Tommy Wood 2:02:22 Um, so, so say you have a wa- so say you have a, an HbA1c of 5.5, but your waist-to-height ratio is close to- Or below 0.5, which I think is a good, a good cutoff. And again, that's been ... Above that is associated with a, a higher risk of mortality. Um, and you have good blood pressure and, and everything else is good, no, I'm not gonna f- focus on decreasing it further. Um, what's tricky about HbA1c is that an H- an HbA1c is supposed to be a picture of your average blood sugar, but you and I could have the same HbA1c and have very different-

Dr. Rangan Chatterjee 2:02:55 Mm-hmm

Dr. Tommy Wood 2:02:55 ... blood sugar over time. Uh, b- for ... Because there are a number of things that affect red blood cells, which are then part of that HbA1c measurement. So say you're at the upper end, you're near the threshold, then I would look at fasting blood sugar. Um, you know, if that looks good, you know, you know, you can ... If you wanna dig even deeper, you can look at, like, how hard, how hard does your blood sugar spike after meals, right? 'Cause if it goes really high and it takes a long time to come down, and you've got a sort of a, uh, a borderline HbA1c, maybe that's, that's, that's a picture of your maybe on the way to having some blood sugar issues.

Dr. Rangan Chatterjee 2:03:25 I guess that's harder for people to measure-

Dr. Tommy Wood 2:03:28 Yes

Dr. Rangan Chatterjee 2:03:28 ... unless they're wearing a continuous glucose monitor.

Dr. Tommy Wood 2:03:31 Yeah.

Dr. Rangan Chatterjee 2:03:32 Because, you know, it's, it's certainly in the UK not that accessible to be able to do something like that. But I, but I agree. And I guess a wider point, Tommy, which I think is worth just pausing on here, is looking at just one of these tests, sure, can be helpful-

Dr. Tommy Wood 2:03:50 Yeah

Dr. Rangan Chatterjee 2:03:50 ... but it's best to look at them in combination altogether. You know, what, what is your blood pressure? What's your triglycerides? What's your A1c? You know, to build up a picture. Would you agree with that?

Dr. Tommy Wood 2:04:02 Oh, uh, absolutely. Um, and I think one thing that particularly individuals who are very health focused is they become too focused on optimizing each individual thing, um, when in reality we have no evidence that that's that important. Um, which is why I think taking the context of, like, one thing being maybe close to a cutoff that somebody said wasn't that great in the ... You know, if everything else looks really good and you feel good, I, I, I mean, I think at that point you should just, you should just stop worrying about it, right? Take it into the context of everything else. Don't, like, hyper focus on every individual number and try and maximize it.

Dr. Rangan Chatterjee 2:04:40 Blood sugar in the context of brain health, cognitive health, right? Just to sort of close that loop a little bit. Um, we're talking about fasting sugar, we're talking about HbA1c, things that people can do. They can see what ... You know, if it needs improvement, if they need to make some changes. But what is the relationship between high blood sugar, uh, raised blood sugar, uh, swinging high and low blood sugars? Basically, what is the relationship between poor metabolic health in, in many ways and brain health?

Dr. Tommy Wood 2:05:17 Some people have called Alzheimer's disease, like the late onset Alzheimer's disease, the age-related dementia we're talking about, type 3 diabetes. Some people may have heard that, and that's because the brain becomes insulin resistant. You see that the brain is able to take up less glucose, and with that you're delivering less of one of those things that we talked about, right? Glucose as an energy source is one of the things that your brain needs, like we talked about earlier. And there are a number of reasons why, why that may happen. Um, but when we see peripherally, when we, when we look, when we measure our blood sugar, there, there was a, a nice study done, I think it was ... Uh, believe it was done in the UK, the, uh, ageing in England study or something like that. And they looked at individuals that had normal blood sugar, uh, pre-diabetes or type 2 diabetes. And within those categories, as you went up each category, the cognitive decline was faster and brain atrophy was faster. So the higher your blood sugar, that's associated with faster cognitive decline within those, within those categories. Either like normal pre-diabetes or type 2 diabetes. And it seems that this is like systemic reflection of your health and is directly affecting the brain. Um, and we see similar things with blood sugar swings. So there, there was a, a nice study done in Japan, uh, and actually a lot of, a lot of studies looking at blood sugar variability have been done in Japan, where they look at, uh, something called, um, the MAGE, the mean amplitude of glycemic excursions, which basically says how big are your spikes in blood sugar? And the bigger your, the bigger your spikes in blood sugar after a meal are cor- is correlated with those things that we talked about, pre-diabetes, type 2 diabetes. So the bigger the spike, the more likely you are to have pre-diabetes or type 2 diabetes or get those, uh, conditions. But related to the brain specifically, uh, this was a trial of a, of a drug to, to treat, uh, di- uh, type 2 diabetes. Um, and at the beginning of the trial, they looked at MAGE, like how, how big are this ... an individual's blood sugar spikes. And of all the things they measured, blood sugar spikes were the best predictors of cognitive function, um, i.e. the bigger the spikes, the worse the cognitive function. But what's really nice and really important is that this effect was reversible. So the greater the ... The more that somebody's spikes improved over the two-year trial, the more their cognitive function improved. So again, it's one of those things where, you know, somebody could say, "Well, I have pre-diabetes, it's gonna affect my brain. There's nothing I can do about it." That's not true. Like, there are studies that show this is reversible. If you can improve your blood sugar control, you can improve your cognitive function.

Dr. Rangan Chatterjee 2:08:01 Yeah. I mean, that's super powerful, Tommy. And again, we're trying to close down this conversation.

Dr. Tommy Wood 2:08:07 [laughs]

Dr. Rangan Chatterjee 2:08:07 There's, there's, there's new avenues being opened up all the time, so we're gonna have to, we're gonna have to commit on air to a part three at some point. Uh, just to finish off, the podcast is called Feel Better, Live More. When we feel better in ourselves, we get more out of our lives. In the context of brain health, right at the end of this conversation, for people who want to optimize their brain health, reduce how much it declines as they get older, have you got any final words for them?

Dr. Tommy Wood 2:08:35 Yeah. It all boils down to, you know, everything we've talked about, um, in relation to the brain and the body. Um, the, the function depends on the demands you put on it, and I mean that in a good way. So do things that are difficult, and then give yourself a period to, to rest and recover. Um, that's it really. It is, it's fairly simple and it c- ... And you know, anything that you enjoy, you know, if you can do it in a social situation, maybe that's even better, right? There are benefits from, from, from social interaction. So a few times a week, spend 20 minutes doing something that's difficult, learning a new skill. Um, and that's probably the, the ... by far the biggest change that you can make to really change the trajectory of your long-term brain health.

Dr. Rangan Chatterjee 2:09:20 If you enjoyed that conversation, I think you are really going to enjoy this one about the daily things you can do to lose weight and prevent disease.

Speaker 2:09:28 I used to think, you know, weight loss is just about willpower. It's about calories in, calories out. The energy balance equation is always true, but people always misinterpret it to mean that just eating fewer calories leads to body fat loss. It does not