How to Enhance Your Immune System | Dr. Roger Seheult

Andrew Huberman 0:00 Welcome to the Huberman Lab Podcast, where we discuss science and science-based tools for everyday life. I'm Andrew Huberman, and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine. My guest today is Dr. Roger Seheult. Dr. Roger Seheult is a board-certified medical doctor in pulmonology, which is the understanding and treatment of conditions that impact the respiratory system, such as colds, flus, and other viruses, mold infections, asthma, and more. Dr. Seheult is also board certified in sleep medicine. He does his clinical work in the intensive care unit at Loma Linda University, and he's actively involved in medical and public health education through his terrific online channel, called MedCram. Today we discuss how to avoid getting colds, flus, and other viruses, and how to treat them to minimize discomfort, accelerate healing, and avoid long-term consequences. During today's episode, we discuss long COVID as well as the use of sun and red light to stimulate mitochondrial, and therefore metabolic health across the entire brain and body. That opens up a broader discussion about phototherapy, which is the use of light to control health, and temperature and other levers for improving brain and bodily function. Dr. Seheult emphasizes that sun and red light therapy have a long and well-established medical history, and their mechanisms of action are known, and therefore it's not just biohacking as many people think. We also discussed the sometimes controversial topic of the flu shot, and if and when you should get one. Dr. Seheult, as you'll soon hear, is world class at making medical concepts and the actionable items related to health exceptionally clear. As a consequence, I'm certain that you'll truly appreciate the knowledge that he shares in your efforts to be and stay healthy at any age. In fact, by the end of today's episode, you'll be armed with the real knowledge on how to best get over nasty infections of the sinuses, lungs, and throat faster should you happen to get one, and even better, how to avoid them altogether. Before we begin, I'd like to emphasize that this podcast is separate from my teaching and research roles at Stanford. It is however part of my desire and effort to bring zero cost to consumer information about science and science-related tools to the general public. In keeping with that theme, this episode does include sponsors. And now for my discussion with Dr. Roger Seheult.

Andrew Huberman 2:16 Dr. Roger Seheult, welcome.

Dr. Roger Seheult 2:18 Thank you so much, Andrew, for having me.

Andrew Huberman 2:20 I discovered you because you were putting out and continue to put out incredible information about how to stay healthy amidst infectious diseases, airborne infectious diseases, skin contact-based infectious diseases, and on and on. And nobody likes to be sick. And you've provided me tremendously valuable information about how to avoid getting sick, and in many cases, how to accelerate the progression from sick to healthy again. It's been, uh, tremendously helpful for getting me back into life, as it were. Let's talk about some of the things that one can do to avoid getting sick when in the presence of airborne viruses, in particular, colds and flus, and other viruses, as it were. If you were to think about the, the major pillars of remaining healthy, especially when one is exposed to colds and flus from kids for, in your case, also in the, uh, intensive care unit where people are coming in specifically because they're sick, often with infections like colds and flus, or worse, you need to take specific precautions to avoid getting sick. What do you think of as the fundamental layer of keeping a healthy immune system to avoid getting sick? And then we'll talk about how to get over and move through being sick more quickly.

Dr. Roger Seheult 3:39 Yes. Well, th- the question is how you avoid getting sick in terms of, uh, infectious diseases, and as it turns out, the answer to that is, is actually the same in terms of avoiding getting sick for anything. And it- it sort of goes to, uh, the pillars, as you call it, in my mind. There's a, there's actually a physician that I, I know very well just outside of, uh, Stanford actually, in a place called Weimar, Weimar University, Dr. Neil Nedley, and he's actually coined this, this mnemonic called NEW START. Um, and- and each of those letters to me in my mind is something that I go to when I want to improve health, uh, in- in people in general. So the N starts for nutrition, and we can talk about nutrition and what that does to the human body. Obviously, you know, as natural as possible, staying away from processed foods, that's something there. Um, exercise is E, and, uh, when I'm talking about exercise, I'm talking about the understanding that we have regarding exercise, not to build muscle necessarily, be stronger. I'm talking about exercise in terms of health, and that has more of a- a J-hook type of- of, uh, picture. What I mean by J-hook is if you're not doing any exercise, you're gonna have higher levels of inflammation. As soon as you start to do some exercise, even mild to moderate exercise, the amount of inflammation in your body starts to come down. But as you start to do more and more exercise, you do have to be careful in terms of your general health. This is exactly kind of what happens with athletes. Um, they have to be very careful that when they're doing that type of elite athletic exercise, that they're not sick on the day of performance. And so that's- that's an issue. So I'm referring to just, you know, mild to moderate exercise is good. Um, the next one would be W, water. Mm-hmm. So this is something that's really interesting. Obviously, it seems pretty, uh, cl- you know, obvious, but not only the use of internal water, but external water. So in that area, we can talk about sauna, cold plunge, things of that nature that can actually help with our immune system. That's a whole i- interesting area of discussion. It involves the innate immune system. It involves interferon. Uh, there's a lot of history and data that goes back over 100 years on how that's been used. START, S-T-A-R-T. So S is sunlight. Mm-hmm. I've been a real proponent of getting people outside into the sun, and we can talk a lot about that. There's a lot of interesting research, not only in terms of sunlight, in terms of influenza, but also COVID, and just about any natural disease. A lot of interesting information there. T-T, uh, stands for the old term called temperance, which you may recall is a, is a term that we use to prevent us from taking in toxins into our body. That's a whole nother discussion. Uh, so staying away from things that would make you sick. A is air. And when I talk about air, it's not just what we focus on, which is keeping bad things out of the air, so having fresh air. But there's a whole discussion to be had in terms of air that has good qualities in it. So, there's a whole area of research that looks at, for instance, phytoncides, which are chemicals that come off of trees. Uh, you may have heard of forest bathing. They've done a lot of research in Japan on this and getting out into nature. There are actual chemicals that are in the air that you can breathe that actually have an impact on your innate immune system. Finally, R, and we'll get into R and T at the end. R is rest. Now, this is, uh, goes without saying, but people who have good sleep habits are going to have much better immune systems. Whether you're talking about the, uh, the antibody response after a vaccine, uh, versus just, um, the number of times per year you're sick. There's very good data, very good research that shows that getting seven, eight hours of sleep a night is going to be very beneficial for your immune system. It has to do with cortisol and beta receptors and all sorts of things. And the last T, which is trust. And, uh, for some it is, is trust in a higher power, trusting God. These are the sorts of things that can help us, uh, relieve stress. If someone else is, is helping you, if someone else is there. T would also include community, people that are around you. These are some of the less, um, uh, tangible ways, uh, of measuring it. But when someone asks me a question, "What can I do to avoid getting sick?" and as you just asked me, in terms of influenza, there's a lot of specific things we can talk about. But that's where I start out with the pillars of health.

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Andrew Huberman 10:46 Let's start off with one of my favorite topics, would be the S in NEW START.

Dr. Roger Seheult 10:51 Yeah.

Andrew Huberman 10:51 Let's talk about sunlight. Listeners of this podcast, or anyone that's heard me on social media, know that I'm, you know, as, uh, big a proponent of getting morning sunlight in one's eyes as one could possibly be-

Dr. Roger Seheult 11:04 (laughs)

Andrew Huberman 11:04 ... without repeating himself 10 million times per year. Uh, it's a daily activity that we just know has such an outsized positive effect on the whole setting of the circadian rhythm, and thereby improved daytime mood, focus, and alertness, and nighttime sleep.

Dr. Roger Seheult 11:19 Yeah.

Andrew Huberman 11:19 But the way you describe sunlight, it goes beyond just getting morning sunlight in one's eyes. So, if we want to parse this S, sunlight, in NEW START, how are you thinking about sunlight? Is it sunlight on the skin? Is it also midday light, not just morning sunlight? Is it a certain amount of sunlight? And then maybe we can also talk about some of the underlying mechanisms.

Dr. Roger Seheult 11:40 Yeah, exactly. So, when you talk about sunlight, and I'm a, a big believer, I'm, I'm board certified in sleep medicine. And I, and I am cheering you on when you talk about these things, 'cause it's so important. That light into the retina does have an effect on the circadian rhythm, suprachiasmatic nucleus. It does have an effect on mood. Goes to the perihabenular nucleus in the brain and has an effect there. Those are well known and very important. Um, what I'm talking about when I'm talking about sunlight is an aspect of light that is not very well known in terms of its visible effects. So, we, we know about the visible effects of light. These are photons that are coming into the eyes that we can see. What I'm discussing and what I'm talking about is the, is the effect of sunlight, uh-... on the human body, the skin, penetrating into the human body. Now, this at first sounds kind of, uh, woo-woo, I guess we could s- say. But the, the point that I want to make here is understanding that when we look at the sun, we are seeing about 38% of that energy coming from the sun is in the visible spectrum. There's a whole nother 52% of the photons coming from the sun in the infrared spectrum. And on the other end, on the ultraviolet side, this is the part we have no problem understanding because we know that ultraviolet B light comes into our skin and it's high energy, so it's able to actually move the bonds on these car- uh, cholesterol derivatives in order to make vitamin D. So we know that. So now what do we say when I say, "Hey, I want to go outside to get some vitamin D"? We know that we're going outside to get this light that we can't see that's very imperative to giving us something called vitamin D, which is, uh, a hormone in our body and it's very, very important. On the other side of that though, on the infrared side, is, is something that there's new science, new data that is coming out that is showing that it's actually very, very important. And for that, I, I would point to a- an article that really changed my, my thinking on this and really opened my eyes, no pun intended. There was an article that was published in 2019, uh, in Melatonin Research by Scott Zimmerman and Russell Reiter. And then the name of that article was Melatonin, Optics of the Human Body, The Optics of the Human Body. And what Scott Zimmerman and Russell Reiter set out to show is that, in fact, um, infrared light, because of its very long wavelength, um, it can penetrate through into the skin actually very deep. And, and we're not talking about how long a, a path length goes through. You have to remember that, that this type of long wavelength can scatter. And it can s- uh, uh, can scatter throughout up to, they say, up to eight centimeters according to this, this data. A single photon? A single photon can bounce around. Mm-hmm. It's, it's a very low energy photon. Uh, but low energy photons, because they're very long in wavelength, can penetrate very deeply. A good way of thinking about this is y- you know, you pull up to a stop sign and a car pulls up next to you and they're playing this really loud music, right? What do you hear in your car? It's very low frequency sound. And the reason why that's what you hear is because low frequency sound is the only kind of sound coming out of that guy's radio that's able to penetrate not only his car, but go into your car and, and shake the steering wheel on your car. Mm-hmm. It's the same thing, like for instance, if you were to go to the Grand Canyon and there's a storm coming, storm very far away. What's the first thing that you're going to hear? Rumbling. It's low rumbling. It's because that low frequency energy is able to penetrate very deeply. Um, there's a astrophysicist in Europe, uh, in England actually, Bob Fosbury. He sent me a photograph of his hand in front of a infrared light source. And it was almost like, uh, uh, the first guy who took a, uh, x-ray of his hand, Roentgen, Ro- Roentgen, I guess is his name. And, uh, he said... He looked at his hand, he says, "I almost, like, saw my own death." 'Cause he could see the bones in his hand through the x-ray. Well, Bob Fosbury, who's, uh, at the European Space Agency and is well-tuned into this type of, of understanding, he put his hand in front of a infrared light sensor or infrared light source and took a infrared light photograph. And the light comes through the hands, it illuminates the entire hand. Uh, and this is of course a lot more than a few millimeters. And the, the mind-blowing thing about it was you could not see any bones. It was either penetrating through the bone or it was going around the bone. And very clearly you could see that infrared light is able to go much more than just skin deep. It penetrates through your clothes. Y- you can t- actually test this out on a, on a, on a summer day or even on a winter day if the sun is out. Wear a few clothes of, uh, layers of clothing, go outside, close your eyes, and move around and see if you can feel where the sun is. You can. And the reason is, is because it's that infrared radiation that's able to penetrate through the clothes, penetrate through your skin, actually activate the heat sensors in your body, and actually go much deeper than that. That's actually in a straight line. After it does that, it hits something and then it bounces around a couple of more times, maybe a few hundred more times. And so the, the point of that paper, the optics of the human body, is that we have this understanding or this idea that light simply hits our skin and that's where it ends. And that's not the case. Why that's important is because of the effect of this type of infrared light has on mitochondria. And that's really the mind-blowing aspect of this, is that mitochondria are like engines in your, in your cells, right? They're like engines in your car. The engine in your car burns fuel, makes locomotion, and in the process of making that locomotion, it creates heat. And that heat, if not dealt with, can shut down your engine. Well, in the mitochondria, you've got this process oc- occurring making ATP, which is basically the currency of energy in the, in the cell. And in the process of doing this, it makes oxidative stress, oxidate reactive oxygen species. If you don't deal with those reactive oxygen species, that could shut down the mitochondria. And, um, and, and quite truly, just about every single chronic disease that we have in this country, whether it's diabetes, hypertension, heart disease, dementia, uh, all of those, they all has, have at the root of them mitochondrial dysfunction. And this, this goes to a, a much bigger picture of the mitochondrial theory of aging. We know that after 40 years, the output of mitochondria, which is ATP, drops by about 70%. 7-0? 7-0. Can you imagine being in your house and somehow the energy production to your house drops by 70%? Can you imagine what an impact that would have on just about every function that goes on in your house? This is exactly what's happening in the cell. And so...What does this have to do with sunlight? Well, here's what they've shown, that m- the mitochondria actually make on site melatonin, in orders of magnitude higher concentration that is made in the pineal gland.

Andrew Huberman 18:51 Really?

Dr. Roger Seheult 18:52 Yes. So, they've actually done the work where they have serotonin.

Andrew Huberman 18:55 Mm-hmm.

Dr. Roger Seheult 18:56 They are actually labeling the carbons in serotonin and showing that, that melatonin in orders of magnitude higher concentration are being made on site in the mitochondria.

Andrew Huberman 19:08 Okay,

Andrew Huberman 19:09 I have to ask about this.

Dr. Roger Seheult 19:10 Yes.

Andrew Huberman 19:10 Most people, including me, are familiar with melatonin secretion from the pineal gland-

Dr. Roger Seheult 19:15 Correct.

Andrew Huberman 19:16 ... being suppressed by light via some neural circuit pathways that go from eye to suprachiasmatic nucleus to... there, there's a, a circuitous loop to the, you know, uh, the brainstem and then up, uh, um, to the pineal. So, light suppresses melatonin release from the pineal. We know that.

Dr. Roger Seheult 19:33 Yes.

Andrew Huberman 19:33 In that context, melatonin is the hormone of darkness and causes sleepiness.

Dr. Roger Seheult 19:40 Correct.

Andrew Huberman 19:42 What is the role of melatonin in the context that you are describing? Because if indeed infrared and long, other long wavelength light is causing the production of melatonin from the mitochondria in the rest of the body, I'm assuming that's not to increase our levels of sleepiness.

Dr. Roger Seheult 20:00 That is correct.

Andrew Huberman 20:01 And I do know that melatonin is a powerful antioxidant.

Dr. Roger Seheult 20:04 Yes.

Andrew Huberman 20:04 So, I'm guessing that next you're going to tell me that it is combating or... the reactive oxygen species that are produced as a function of mitochondrial, uh, metabolism.

Dr. Roger Seheult 20:15 A- absolutely.

Andrew Huberman 20:16 Okay.

Dr. Roger Seheult 20:16 Absolutely. So the, the mitochondria make melatonin on site. This is not being secreted into the blood. It's being used on site. So this is not being used as a secondary messenger to tell the body anything about circadian rhythm. This is a extremely powerful, as you know, extremely powerful antioxidants. It's actually one of the most powerful antioxidants in the human body. It actually upregulates the glutathione system, by regulation. So what this melatonin does is it's able to mop up these reactive oxygen species. Let's, let's back up a little bit there. Reactive oxygen species. What are they? So if you, if you... let's get, let's get nerdy. Let's get into the details. In the mitochondria, the way it works is that you burn fuels, you burn carbohydrates, proteins and fats. And as a result of that, you make these very reduced agents, NADH, FADH2. They go to the electron transport chain. And as... just as the Colorado River, as it goes down through various different dams and then dumps out into the Gulf of California, the same thing happens with these very highly charged and electro-negative electrons. They... as they start to fall down and get transferred from one, uh, uh, enzyme to another, they cause the out, out production or the out... a transfer of protons into the inner membrane space. The problem is though, is when you finally get done with these electrons, they've been completely spent. There's nothing else to accept them. And the only thing that can actually do that is something so electro-negative that it would actually take these electrons. And that's oxygen. And that's the reason why we breathe oxygen. It's, it's because we need an electronic acceptor for these spent electrons. It's very near and dear to my heart as a pulmonologist, a critical care specialist. I, I... we need to have oxygen. If you don't have oxygen, things shut down very quickly.

Andrew Huberman 22:07 For those that aren't familiar with these biochemical pathways, maybe one way for them to think about it is that free electrons are not a good thing in this system.

Dr. Roger Seheult 22:15 No.

Andrew Huberman 22:15 You don't want electrons floating around and... in these biochemical steps that convert energy into the stuff that cells can use more readily to move and do everything that we do-

Dr. Roger Seheult 22:26 Right.

Andrew Huberman 22:27 ... electrons are kicked off. Oxygen can work with those free electrons. I'm trying to use language here that-

Dr. Roger Seheult 22:34 Yes.

Andrew Huberman 22:35 ... you know, divorces us from the, from the, uh, you know, the-

Dr. Roger Seheult 22:37 Biochemical.

Andrew Huberman 22:38 ... the classic, uh-

Dr. Roger Seheult 22:38 Yes.

Andrew Huberman 22:39 ... biochemical pathways so that more people can grasp it-

Dr. Roger Seheult 22:41 Yeah.

Andrew Huberman 22:41 ... 'cause it's really a beautiful mechanism. I- so if you have a, a positive charge to, uh, effectively work with the, the free negative charge, then, um, the system is, is stabilized or at least isn't pushed in, in the direction of inflammation. This is... many people have heard of free radicals-

Dr. Roger Seheult 22:58 Exactly.

Andrew Huberman 22:58 ... and that's what we're referring to.

Dr. Roger Seheult 22:59 Exactly.

Andrew Huberman 23:00 You want to, you want to offset the free radicals.

Dr. Roger Seheult 23:02 Correct.

Andrew Huberman 23:03 Uh, and to the biochemists out there and the biologists-

Dr. Roger Seheult 23:05 (laughs)

Andrew Huberman 23:05 ... I'm using the term offset, uh, loosely. Um, okay. So melatonin, in the context of how sunlight can activate melatonin within cells, maybe it's, um, worth pointing out to people that when the pineal gland releases melatonin to make you sleepy, that's an endocrine or hormone type mechanism. Hormones act on local tissues and more distant tissues in the body.

Dr. Roger Seheult 23:30 Correct.

Andrew Huberman 23:30 Pheromones act between bodies.

Dr. Roger Seheult 23:32 Right.

Andrew Huberman 23:32 Right? In the context that you're describing, melatonin is acting within cell.

Dr. Roger Seheult 23:36 Correct.

Andrew Huberman 23:37 Okay.

Dr. Roger Seheult 23:37 So let's, let's think of the... let's think of this dichotomy. The mitochondria always needs to have antioxidants, otherwise it's going to become damaged. Like if these free radicals are produced, the very next molecule that they bump into, it's going to change it. And if that's the mitochondria, the mitochondria is going to be damaged. So it needs a cooling system. Just like your car has a cooling system for heat, the mitochondria needs a cooling system for oxidative stress. What's the cooling system during the day? Sunlight comes in, activates these... uh, it upregulates melatonin, which does that. Well, when there is no sunlight, what is the cooling system then? It's the system that we've always known about. And the reason why we've always known about it is because we can draw blood samples. It's much easier to detect melatonin in the blood because we've developed techniques first to detect things in the blood. But what we're talking about now is how do we detect things not only intracellular, but intra-organelle. That's much more sophisticated, yet now we do have the technology to show, and the amount of melatonin we're talking about is 20 times higher......than we're picking up in the blood. So at night, the system is melatonin is secreted from the pineal gland. It goes into the blood, diffuses into the cell, diffuses into the mitochondria, and does the job.

Andrew Huberman 24:54 Do you think that that role of melatonin from the pineal at night is part of the reason why sleep is so restorative?

Dr. Roger Seheult 25:01 Absolutely.

Andrew Huberman 25:03 It's probably no coincidence then that when we fall asleep, it's at least correlated with, and in many ways caused by, the reduction in core body temperature. Like, it's very unusual for melatonin levels to be high when body temperature is high.

Dr. Roger Seheult 25:19 Yeah.

Andrew Huberman 25:19 Be- these things normally are coordinated at night. I'm not aware that it actually drops body temperature, but it might. I, I'm just not aware of the literature. But what you're describing is amazing. I mean, first of all, most people's minds, including mine, are going to be blown by the fact that long wavelength light can actually go through clothing-

Dr. Roger Seheult 25:36 Yes.

Andrew Huberman 25:37 ...and skin. And so you can imagine that if you have a minimum of clothing on, whatever's appropriate for that-

Dr. Roger Seheult 25:41 Yes.

Andrew Huberman 25:41 ...context, and you get some sunlight on your skin, even on a cloudy day-

Dr. Roger Seheult 25:44 Yes.

Andrew Huberman 25:45 ...some of this should be coming through. We could talk about that. It's more UV light-

Dr. Roger Seheult 25:48 Yeah.

Andrew Huberman 25:48 ...short wavelength light, that's going to break through thick cloud cover.

Dr. Roger Seheult 25:51 Correct. Uh, cloud cover, because it's water vapor, and water vapor does absorb infrared. It will be substantially less, but much more than being inside.

Andrew Huberman 25:59 And on a clear day or partially cloudy day, uh, we're getting a lot of red light, long wavelength light, and infrared and near infrared light coming through.

Dr. Roger Seheult 26:08 Absolutely.

Andrew Huberman 26:08 I think a lot of people don't realize that, because in this age of, of red light devices and infrared light devices, um, of which I own one and I love and I use, um, but people forget that the, uh, the primordial and arguably, I'll, I'll say, the best source of red light and near infrared light and infrared light of the sort that we're talking about right now is going to come from the sun.

Dr. Roger Seheult 26:32 100%.

Andrew Huberman 26:32 I mean, there's no device that can replace the sun.

Dr. Roger Seheult 26:35 100%.

Andrew Huberman 26:35 Okay.

Dr. Roger Seheult 26:35 100%, yeah.

Andrew Huberman 26:36 Okay, great. So,

Andrew Huberman 26:39 how does this keep us safe from infection? As long as we're here-

Dr. Roger Seheult 26:44 Yeah.

Andrew Huberman 26:44 ...um, what else is it doing to offset the 70% reduction in mitochondrial function? 'Cause what we're talking about now is, um, the role of melatonin within cells to, um, lower temperature and reduce these, uh, reactive oxygen species.

Dr. Roger Seheult 26:58 Yes.

Andrew Huberman 26:58 Does that somehow offset the reduction in mitochondria that normally occurs?

Dr. Roger Seheult 27:02 It does. And so there's a- so the increase in melatonin from infrared, uh, radiation going into the mitochondria is one aspect. There's a whole host of other aspects that occur. There is, uh, cytochrome 4 oxidase. Again, one of those enzymes in the electron transport chain, uh, can absorb infrared light. There's nitric oxide. What, what the whole effect of this is, and the bottom line is, is that when you have red light to near infrared light getting in that deep, there is a increase in the efficiency of the mitochondria. So this is the key point because if, in fact, with the theory of mitochondrial aging, that we're having a decrease in the efficiency of the mitochondria as we get older, if there is something that we can do to reverse that or to at least prevent that from happening, that can have a tremendous impact in our health overall. So two points. One, uh, one point about infrared light and its characteristic, and then number two, let's actually get to some data because we're s- we're saying a bunch of things, but what we really need is evidence-based stuff. Okay, so the first thing, there's one other thing that I should mention about the effect of infrared light, especially in nature, and that is, is that not only can it penetrate through clothes. You may remember the Sony Cam, uh, night vision thing, uh, back in the '90s where Sony came up with a night vision camera that you could take pictures at night, and some enterprising youth, probably a man, figured out that you could use it during the day and you could see through clothes.

Andrew Huberman 28:31 And, uh, presumably, they took that off the market.

Dr. Roger Seheult 28:33 They took it off the market pretty quick, yes.

Andrew Huberman 28:35 (laughs)

Dr. Roger Seheult 28:36 Um, but there's one other thing that's really important to understand, too, and that is, is that, believe it or not, but the leaves on trees and grass, anything with chlorophyll, is highly reflective of infrared light. What that means is, is that if you go out, outside on a sunny day versus going outside on a sunny day surrounded by green, green spaces, you're going to get probably two, three, four times more infrared light in that environment than you would without that environment. If you, you can, you can check this out. You go to Google and just type in infrared photography and click images, and you will see any kind of infrared filtered light when it shows a tree or grass, it, it looks like it's lit up, like it's got snow on it. It's bright white. It's very reflective. On a hot summer day, if you go outside and touch some object that's in the sun, it's going to be extremely hot. Touch a leaf, it's, it's not hot at all. It's because it's reflecting that light. In fact, the coolest place in a garden on a hot summer day is where? It's under a tree. Because all of that, all of that infrared light is being reflected off. So, and, and just to jump ahead here, but we know from years and decades of data that people who live in green spaces have reduced diabetes, reduced hypertension, reduced mortality, just living in green spaces.

Andrew Huberman 29:59 Is it possible to tease away that effect from the other things associated with living-

Dr. Roger Seheult 30:04 Yes.

Andrew Huberman 30:04 ...in green spaces? Because fortunately, our audience is trained to think scientifically and they'll know, well, it's not necessarily causal, right?

Dr. Roger Seheult 30:10 Yes.

Andrew Huberman 30:10 People who live in green spaces tend to walk more. They tend to perhaps eat more fruits and vegetables and on and on.

Dr. Roger Seheult 30:15 Correct. So, so, uh, getting onto that, uh, there was a study that was just done in Louisville, Kentucky. Four square miles, they measured everybody in that four square miles HR- HSCRP. What's HSCRP? It's basically, it- it's a surrogate marker for inflammation in the body.

Andrew Huberman 30:33 Mm-hmm.

Dr. Roger Seheult 30:34 And then they did this, they did something incredible. They brought in 8,000 plus trees, mature trees, and they planted those trees in that four square mile area. Took them about a year. Two to three years later, they went out.Nothing, the, the income of these people living in this four square mile area did not change. The, uh, presumably, they did not do any exercise programs in this area. Everything was the same. The only thing they did was plant trees. And they went out and they rechecked everybody's highly sensitive CRP levels. They dropped by 13%.

Andrew Huberman 31:08 Wow.

Dr. Roger Seheult 31:09 And that's about on the order, almost on the order of doing, uh, exercise three times a week.

Andrew Huberman 31:15 I should mention that, um, CRP, C-reactive protein, has been associated with a number of blinding eye diseases, um, uh, associated with inflammation and basically, um, everything bad you can imagine in every organ of the body, heart attack, uh-

Dr. Roger Seheult 31:30 Stroke.

Andrew Huberman 31:30 ... ischemia.

Dr. Roger Seheult 31:30 Yeah.

Andrew Huberman 31:31 Yeah, this kind of thing. Um, incredible.

Dr. Roger Seheult 31:34 Yeah.

Dr. Roger Seheult 31:35 So let's, let's actually look at some data. So we've talked about, you know, any astute person listening to this is like, "Okay, so you talked about a lot of observational stuff. Is there any interventional stuff?" So I, I, uh, turned to Glen Jeffrey, who's, um, uh, he's in the Department of Ophthalmology. You, you know him well, actually, at, uh, University College London. And he's done s- some really interesting experiments in the last two to three years looking at red light. One of them was, uh, the first one that he did was he took, um, uh, older subjects who had difficulty with color sensitivity in their vision, and he exposed them to 670 nanometer, which is red, it's visible, light for just three minutes in the morning. It only worked in the morning in this case, which is interesting.

Andrew Huberman 32:20 Mm-hmm.

Dr. Roger Seheult 32:21 And he showed that there was a 17% increase in color sensitivity that lasted for days. Now, why would that be? Again, you should know that the retina is the, the one tissue in the human body that has the highest concentration of mitochondria. And if you understand y- what's going on in light, and I know you do, but our, our audience might not, is when you have visible light coming in to the retina, it is causing a photochemical reaction that requires a tremendous amount of energy. Vesicles budding off, things, uh, diffusing, uh, electrical conductions being... And it has to happen very, very quickly. Otherwise, what you see is going to be there as a blur. So this is constantly being updated. So it's no surprise that, you know, mitochondria is, is so, uh, concentrated there. So what's actually going on there? What we believe is going on is that this red light is actually stimulating these mitochondria to produce more ATP and it's improving the sensitivity. But the, the, the coup de grace or the, the pièce de résistance was his next study which he did, where he took 30 subjects, he gave them 75 grams of glucose, and in a blinded way, uh, so they couldn't tell w- what was, if the light was on or off, he exposed their backs to the same 670 nanometer light, and he, he monitored their glucose over time, uh, over the next two hours basically, uh, multiple points. And what did he find? He found that those that were exposed to red light and didn't know it had lower glucose concentrations. So he surmised that the mitochondria were working more efficiently, they were using up more energy, and this is the reason why the glucose didn't peak as high. But he couldn't be sure unless he also monitored for the output of metabolism. So what happens when the mitochondria is working? It's making carbon dioxide. So he also measured carbon dioxide. And sure enough, those subjects that had the intervention of the red light had statistically significantly higher carbon dioxide levels on exhalation.

Andrew Huberman 34:20 Awesome. Too bad the guy's in England.

Dr. Roger Seheult 34:23 (laughs)

Andrew Huberman 34:23 That's a joke about, for my British friends. Uh, yeah, it tends to be very overcast there.

Dr. Roger Seheult 34:27 Yes, yeah.

Andrew Huberman 34:27 But the sun does come out in England as well.

Dr. Roger Seheult 34:29 So, so here we have basically, this is a randomized controlled intervention trial, which showed that red light's doing this. And there's a whole host of other, uh, o- other trials that show the same thing. So when I started to see this in my patients and, and what caused me to even do this, you might ask, "What's a pulmonary critical care doc talking about mitochondria in the eye?" What really spurred me on to look at this was when I was in the middle of something called the COVID pandemic, and I was seeing patients in my ICU that were, that were dying. And what were they dying of? COVID, but what were they in there for? They had things like diabetes, hypertension, dementia, um, all of these things which have at the root of them mitochondrial dysfunction. So what we have is, is an epidemic, I believe, of mitochondrial dysfunction. And how are we going to repair that? I think sunlight is one of the ways to do it. So I started looking around at the evidence. Um, there was a study that was done, Oxford and the University of Leiden in Netherlands, where they looked at about 10,000 subjects. They just drew their blood and they said, "Let's just check triglycerides and insulin sensitivity." And then what they did was they looked over the previous 10 days at the weather report, and they were able to show that by the hour, the more sunlight that there was in the previous seven days, that actually predicted an improvement in insulin sensitivity and a reduction in triglycerides. That fast, over a seven-day period of time. There was another study that was done. This was in Sweden. Uh, so this was an epidemiological study, but maybe actually showed some causation. They looked at Swedish women. It was about 30,000 Swedish women living in, uh, Sweden at the time, of course. And they divided them into three groups. Those that avoided the sun, those that got moderate sun exposure, and those that got a lot of sun exposure. And what they showed after following them for 20 years, so long period of time, was that those women that were out in the sun not only had lower all-cause mortality, but they also had lower cardiovascular mortality. And what's really interesting is they had lower cancer mortality, and it was in a dose response curve, which suggests Bradford Hill criteria that there was maybe some causation here.What was really interesting about that study is that they looked at smoking. So, what was the difference here? It wasn't a small difference. It was actually such a large difference that the sunlight made, that they were able to show that those women in Sweden who were in this study, who went out into the sun avidly and smoked, had the same mortality as those women who avoided the sun and didn't smoke. The first thing that hit my mind was, is what do we, what do we do to people here in this country that want to smoke? We tell them to go outside. (laughs)

Andrew Huberman 37:33 (laughs) I'm not encouraging people to smoke.

Dr. Roger Seheult 37:35 (laughs)

Andrew Huberman 37:35 Uh, clearly the best outcomes are going to be from not smoking-

Dr. Roger Seheult 37:39 Of course.

Andrew Huberman 37:39 ... um, and from getting sunlight. But it is-

Dr. Roger Seheult 37:41 Yeah.

Andrew Huberman 37:42 ... a remarkable study.

Dr. Roger Seheult 37:43 I mean, this is the, certainly, I-

Andrew Huberman 37:44 Yeah.

Dr. Roger Seheult 37:44 ... smoking would be under the T for temperance.

Andrew Huberman 37:47 Yeah.

Dr. Roger Seheult 37:47 That would be where I would put a NEWSTART. We- we would not want to do that. But it, that same study was repeated basically again, University of Edinburgh, they did a biobank study, 10 times the amount of people, 400,000. Repeated the study, showed exactly the same, both men and women. Uh, except this time, they actually measured UVA. So, they used, uh, ultraviolet A radiation as a surrogate for infrared and for sunlight in general. They found exactly the same thing, reduction in mortality. Such so is the evidence that even dermatologists are starting to rethink. There was an article that was published in the Journal of Investigative Dermatology-

Andrew Huberman 38:29 Mm-hmm.

Dr. Roger Seheult 38:29 ... by Richard Weller, and, uh, the name of that article was published last year. It was titled, uh, Sunlight, Time for a Rethink.

Andrew Huberman 38:37 Mm-hmm.

Dr. Roger Seheult 38:38 And he said, "Look, there are societies that are seeing this and they're already saying that there's a potential benefit for getting out into the sun."

Andrew Huberman 38:46 Yeah, the, um, dermatologist that I hosted on this podcast, uh, Dr. Teo Soleymani, um, also happens to be a derma oncologist, so his specialty is skin cancers. And, um, I was surprised to learn, but, you know, we've talked about it several times now offline as well, Teo and I. I was surprised to learn that the sunlight-induced cancers of the skin, while they do exist, that's real, right? You get too much-

Dr. Roger Seheult 39:13 Of course.

Andrew Huberman 39:14 ... UV exposure, you're going to, um, age your skin more rapidly. You're, uh, going to increase the likelihood that you'll get a skin cancer. However, this was really surprising to me. According to him, there is no evidence that sunlight induces the deadly types of cancers like melanoma. Those are more genetically determined.

Dr. Roger Seheult 39:34 Yeah, yeah.

Andrew Huberman 39:35 That's not to say that sunlight can't damage skin, but it is really interesting that more and more data and clinical trials included are pointing to exactly what you're saying, which is that more sunlight exposure is beneficial.

Dr. Roger Seheult 39:50 Yeah.

Andrew Huberman 39:50 And the risks of sunlight exposure can largely be offset by limiting your exposure to excessive UV. And it's pretty easy nowadays with any app, um, a lot of zero-cost apps out there. I can put, uh, links to one or two in the show note captions that I like that have no affiliation to whatsoever, by the way, um, will tell you when the UV index is highest. It's in the middle of the day typically.

Dr. Roger Seheult 40:11 Yeah.

Andrew Huberman 40:11 And so it's possible to get plenty of sunlight on your skin without exposing yourself to excessive UV.

Dr. Roger Seheult 40:17 Yeah, and I'd even take it a step further because we- we know that a single layer of clothing can actually, is pretty good at blocking ultraviolet light, right? But remember we talked about infrared. Infrared can penetrate through. So, if someone is fair skin and they're concerned about getting skin damage, wear a broad-brimmed hat, put a- put a- a long-sleeved shirt on, but get outside because that's where the infrared... Especially if you're around, uh, you know, green, uh, green, uh, shrubs and- and- and leaves and things 'cause that's where you get a lot of infrared light. We know that green spaces are- are- are beneficial in terms of that, and we've talked about, you know, Louisville, Kentucky, that there's a benefit there just by putting the tree there.

Andrew Huberman 40:59 I love those data.

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Dr. Roger Seheult 43:32 In terms of your original question, which is, uh, getting back to influenza or-

Andrew Huberman 43:37 Mm-hmm.

Dr. Roger Seheult 43:37 ... flus or things. So there's a stu- there's a great study that I always love to talk about, uh, in terms of this, and it was, um, actually done by Harvard. It was at Harvard Kennedy School, uh, um, which is not the medical school. This is the p- public policy, politics school. And what they did was they looked at this very question of influenza and why do we always get it in the wintertime and what's, what's potentially beneficial for it? And the problem is, is that we always have this influenza season, which is in the wintertime. We can talk about why that might be. I would suggest to you that it's because that's when we have the shortest day of the year. But we also have other things that happen at that time, right? What else is happening? We're having parties at that time. There's, there's Thanksgiving, there's New Year's. It's cold. You know, does the, does the temperature have anything to do with it? Uh, we're also inside because it's cold. So what is it that's actually doing it? Well, 2009 was a banner year, because 2009 was the year that we had the H1N1 pandemic, and that was a boon for us. The reason is, is because, not because of the deaths that we had, but from scientific standpoint, this epidemic actually peaked in the summertime, and it was in areas where the humidity was sometimes high and sometimes it was low, and sometimes the temperature was high, sometimes the temperature was low, sometimes the sun was out, sometimes it was cloudy. In other words, we uncoupled the influenza virus in 2009 from it being in the wintertime and all of those things that were associated. So now we have all of these data points, and so Harvard went to work at looking at all these data points. They looked at solar, uh, radiation data at that time, and they were actually able to look specifically where that person came from and what was the solar radiation in that particular area, and what they came up with was, absolutely. They said, quote, "Sunlight strongly protects against getting influenza." It was a, uh, an amazing study. Um, I'm reminded of a study that was published in COVID. Uh, this was published in 2021, and it was looking at this very question. Is it temperature, is it humidity, or is it sunlight? So what they did was they looked at the autumn surge of COVID in the wintertime in Europe, in autumn, actually, and they asked this question. When there was the surge date in this country, whatever country it was in Europe, when did it happen and what were the things that caused it to happen? So they put all the data out there for temperature, and it was a flat line. There was, uh, uh, temperature did not predict which country, how the country got, uh, COVID-19 when the surge st- started to happen. They did the same thing for humidity. Flat line. When they got to latitude, it was a perfect correlation. In other words, as the sun in the wintertime started to peel back off of the Northern Hemisphere, it started to sink below the equator. And when there was a critical period of time that the day shortened to the point where at first Finland got a shor- the shortest day or a short enough day, and then, and then Germany, and then further on, what it showed was latitude actually perfectly predicted when the surge dates would happen, starting off with Finland and ending up with Greece at the bottom.

Andrew Huberman 47:04 Wow. Do you see influenza at the equator?

Dr. Roger Seheult 47:08 You do see certainly influenza at the equator, but what's really interesting about that is that if you look at, for instance, uh, the, the influenza, uh, mortality in the United States, obviously in the Northern Hemisphere, what you will see is you will see it peak generally one to three weeks after the shortest day of the year.

Andrew Huberman 47:31 Hmm.

Dr. Roger Seheult 47:31 Which is around now, in J- in December and January. Now, if you look at Australia, what do you think you'd see?

Andrew Huberman 47:39 The inverse.

Dr. Roger Seheult 47:40 Exactly. It's, it's actually, in Australia, the influenza season peaks late June, early July.

Andrew Huberman 47:47 Mm-hmm.

Dr. Roger Seheult 47:47 So if you now, now go look at something like the Singapore. Singapore is, I think, within 100 miles of the equator. You will see that in Singapore, there are, there is influenza peaks and troughs, but it's not seasonal.

Andrew Huberman 48:01 Hm.

Dr. Roger Seheult 48:01 It's just almost random.

Andrew Huberman 48:04 Is it not the case that, um, in hospitals and other, um, recovery wards, as it were, uh, that there used to be classically, there was a, uh, a habit of putting people out into the sun, like sun decks on the roof of hospitals and things of that sort?

Dr. Roger Seheult 48:24 I'm smiling because you, you're absolutely correct. You're absolutely correct. And, and as I started to go through this and look at this, I started saying to myself, "We need to get people out in the sun." And then I realized not only am I not the only one saying this, but certainly this was being done 100 years ago, 150 years ago.

Andrew Huberman 48:41 Just as a speculation-

Dr. Roger Seheult 48:42 Yeah.

Andrew Huberman 48:42 ... wh- why do you think we've migrated away from this-... frankly, basic biochemical cellular understanding of how the sun can benefit us. I mean, I feel like so much attention has been paid to how the sun can damage our skin and, quote-unquote, give us "skin cancer," that perhaps we overshot the mark.

Dr. Roger Seheult 49:00 I think it has to do with scientific reductionism. And what I mean to say by that is we've had a lot of data that shows that ultraviolet light can cause cancer. And so, we've assumed that anything that has ultraviolet light can cause cancer. There's this complete dismissal of the fact that this ultraviolet light is packaged for the entire existence of human nature, along with infrared light. And, and if you, it's, it's a beautiful thing when you start to look at this, because you start to realize that the infrared, we, we never get blue light or ultraviolet light ever without the presence of infrared light.

Andrew Huberman 49:39 Unless it comes from an artificial source.

Dr. Roger Seheult 49:41 Exactly.

Andrew Huberman 49:43 So, this is really the first time-

Dr. Roger Seheult 49:44 Exactly.

Andrew Huberman 49:44 ... in human history that we've had this preponderance of short wavelength, AKA blue, uh, and green light, in the absence of red light. In fact-

Dr. Roger Seheult 49:52 Yeah.

Andrew Huberman 49:52 Maybe, maybe we should just spend a couple of moments talking about what kind of sunlight exposures you recommend for people, depending on time of year.

Dr. Roger Seheult 49:59 Yeah.

Andrew Huberman 49:59 And then after that, I'd like to talk to you briefly about this shift away from incandescent bulbs to-

Dr. Roger Seheult 50:05 Oh, yes.

Andrew Huberman 50:05 ... uh, indoor lighting with LEDs. But just to make sure that, um, I don't move us along before, uh, providing some of the key, uh, takeaways.

Dr. Roger Seheult 50:15 Yes.

Andrew Huberman 50:16 How much sunlight should we get each day in the shorter days of winter, and in the fall? And, and when should this be done? In the Jeffrey Study, it was clear that there was circadian regulation, as you mentioned, getting that sunlight, or excuse me, getting that red light, infrared light into one's eyes early in the day was important.

Dr. Roger Seheult 50:31 Yeah.

Andrew Huberman 50:32 If I'm living a standard life of, of work and job and people are managing kids and all sorts of things, sometimes it's hard to get into the sunlight because you're just following a schedule. How much time each day do you recommend, independent of anything, get, you know, related to getting sunlight in one's eyes for circadian rhythm setting?

Dr. Roger Seheult 50:49 Right.

Andrew Huberman 50:49 So, how much time, what time of day-

Dr. Roger Seheult 50:52 Yeah.

Andrew Huberman 50:52 ... and what frequency across the week?

Dr. Roger Seheult 50:55 Excellent question. And, and you've hit on exactly the issue. Uh, based on Glenn Jeffrey's studies, based on another study that was actually done in Brazil, it was actually an interventional study in COVID that showed that just 15 minutes a day for seven days was enough to actually get people with COVID out of the hospital faster. This was a randomized placebo control, double-blinded. Amazing study. 940 nanometers. So, when I talked to Glenn Jeffrey about this, he says he sees it in humans, he sees it in bees, he sees it in insects. It's all the same. The mitochondria behave exactly the same.

Andrew Huberman 51:34 When you say 940 nanometers, you're talking about long wavelength light coming from an artificial source?

Dr. Roger Seheult 51:38 Correct.

Andrew Huberman 51:39 Okay.

Dr. Roger Seheult 51:39 Yeah, that was 940, and it was actually very low. It was about 2.9 milliwatts per square centimeter.

Andrew Huberman 51:45 So lower e- energy. Most people-

Dr. Roger Seheult 51:47 Yes.

Andrew Huberman 51:48 ... um, are not going to own a f- a red, in far inf- uh, a red, a far red, or an infrared light. So-

Dr. Roger Seheult 51:56 Yes.

Andrew Huberman 51:56 ... um, I just want to emphasize again for people, you can get that wavelength and all the other relevant wavelengths from the sun.

Dr. Roger Seheult 52:02 Exactly.

Andrew Huberman 52:03 That's your, that's your red light therapy, folks.

Dr. Roger Seheult 52:04 Exactly.

Andrew Huberman 52:05 Yeah.

Dr. Roger Seheult 52:05 And this is what I'm trying to say is like, this is not like some powerful laser that they were using. This is 2.9 milliwatts. I mean, sunlight, all sunlight is about 100 milliwatts per s- per centimeter squared.

Andrew Huberman 52:17 By the time it reaches... Uh, uh-

Dr. Roger Seheult 52:19 Through the atmosphere.

Andrew Huberman 52:20 Through the atmosphere.

Dr. Roger Seheult 52:20 Yeah, so 130, uh, when it hits the atmosphere. By the time it hits you, it's about 100. If you're looking at just infrared light, we're talking about 20, uh, milliwatts per square centimeter. And so this was 2.9 at a very specific wavelength. So, something that's completely doable.

Andrew Huberman 52:36 Okay.

Dr. Roger Seheult 52:36 Okay? And so what they did, it was 15 minutes a day for seven days. And what, uh, what Glenn Jeffrey was telling me is that, "Roger," he says, "Roger, it doesn't matter if I do, if- if it's in insects, if it's in bees, if it's in humans." Once you hit a certain point, 15, 20 minutes, diminishing marginal utility. The- the- the- the improvement after that point is so minimal that you only need about 15 to 20 minutes. That's why he was able to do his experiment in the eye for three minutes, was all that was necessary.

Andrew Huberman 53:07 So, is this 15 minutes outside in the first three hours of your, of your conventional day, as I call it?

Dr. Roger Seheult 53:13 I-

Andrew Huberman 53:14 'Cause people will say, "Well, the sun comes up later this h-"

Dr. Roger Seheult 53:16 Yeah.

Andrew Huberman 53:16 Conventional day, meaning after the sun l- after the sun has crossed the horizon, is, he has risen.

Dr. Roger Seheult 53:20 I don't think it matters. I don't really think it matters. I think it, what would, what would matter is if there's a lot of ultraviolet light, which would be when the sun is high. And for people who are skin-sensitive, that could be an issue. But if you're covering up, it doesn't matter. And, and here's the issue. The issue is, is that when you need it the most, in the wintertime, is when it's the hardest to get.

Andrew Huberman 53:40 Mm-hmm.

Dr. Roger Seheult 53:41 So, you really have to make a concerted effort. And for a lot of people, and this is, this is what happens probably right after November, and probably going through to mid-January, is this what happens. People get up in the morning, they go to their car, they get into their car, they drive to work. The sun's not up yet. They get to their work, the sun comes up, but they're inside. Then what happens is, they get done with work, the sun is already down. They come home from work. And so there literally is weeks on end that occur where they're not even getting 15 minutes of sunlight. And I think this is the reason why we have the influenza surge at this time. Uh, if you look to see, the EPA did a study and they looked at Americans. 93% of our time is spent inside. 86 inside a building, six to 7% inside of a vehicle.

Andrew Huberman 54:29 And this is a relatively new thing.

Dr. Roger Seheult 54:31 Yeah.

Andrew Huberman 54:31 I mean, when, certainly when I was growing up-

Dr. Roger Seheult 54:32 Yeah.

Andrew Huberman 54:33 ... if I came home and had a snack after school, I was getting kicked out of the house-

Dr. Roger Seheult 54:37 (laughs)

Andrew Huberman 54:37 ... to go outside.

Dr. Roger Seheult 54:38 Yeah.

Andrew Huberman 54:38 My, you know, it was k- it was, uh, routine for parents to tell kids they had to go outside.

Dr. Roger Seheult 54:44 Yeah.

Andrew Huberman 54:44 And I think there's also, um, it's also the case, as you mentioned, that, um, we're working a-... later, or at least on devices later into the evening.

Dr. Roger Seheult 54:55 Yeah.

Andrew Huberman 54:56 Which means there's more exposure to short wavelength light from devices and artificial sources.

Dr. Roger Seheult 55:00 Absolutely. Absolutely. So my recommendation, which is what the original question was, is take your lunch break outside. It's something as simple as getting outside, even if it's at lunchtime. Yes, the ultraviolet is probably the highest at that point, but if that's the only time that you're going to get sunlight, take

Dr. Roger Seheult 55:18 it. Now for some, you know, we can say this, I can say this, I live in Southern California. I'm blessed by 300 and some odd days of sunlight every year. What do you do when you're in Boston? What do you do if you're in New York? What do you do if you're in England, in Sweden, in, uh, uh, these places where there isn't a lot of light? Well, there's a study that was done looking at infrared lamps, right?

Andrew Huberman 55:39 Mm-hmm.

Dr. Roger Seheult 55:39 So you've got to be careful there because if the infrared lamps are too high in amplitude, this result from infrared light in the body is something known as a biphasic response, and that's really important to understand. Don't come into this if you're going to get a red light therapy and think that more is better, because more may not be better. Um, you actually could do detriment if you have the red light at too high of a level. So I would match it to what we're getting from the sun. As you said, the sunlight is your best infrared or red lamp. So there was a study that was done looking at well-being, and they did a red lamp, red light lamp, infrared light, so it was coupled with 850, I think was the nanometers, so that is definitely in the infrared spectrum.

Andrew Huberman 56:26 Yeah, you can't see that.

Dr. Roger Seheult 56:27 Cannot see it.

Andrew Huberman 56:27 No.

Dr. Roger Seheult 56:27 And they had it set up at a desk that s- some guy was, uh, sitting in front of for four hours a day for eight weeks, and they did this study and they, they did it in the summertime and they did it in the wintertime. And this is really telling. There was no effect on the subject when they looked at those that had it in the summertime. I would say probably because they were getting plenty of infrared light-

Andrew Huberman 56:48 Mm-hmm.

Dr. Roger Seheult 56:48 ... elsewhere. It was onl- they only showed a statistically significant effect in the wintertime. And so if you look at influenza, I would even go beyond that. Look at a chart of the United States throughout the entire year, and look at all of the natural causes of death, not just influenza and pneumonia. Look at cardiac disease, look at, look at, uh, kidney disease, Alzheimer's disease. All of those deaths go up all at the same time, and they all go up about one to three weeks after the shortest day of the year. And they all come down and they all are at their nadir about one to three weeks after the longest day of the year. When you see that and you s- you just start to just digest what you're seeing there, and then you start to understand that infrared light from the sun, which we have filtered out with LEDs and all this, and we can get to that, all of that's gone, that we're spending 93% of our s- our time indoors. Put that all together and the fact that infrared light helps the mitochondria and the fact that the mitochondria is at the, sort of the core of all of these chronic diseases that we're battling, it- it- it really wakes you up and you start to realize that maybe the lowest hanging fruit that we can do right now today, for literally no money, is simply to just work on getting more sun exposure in the wintertime.

Andrew Huberman 58:11 Two questions.

Dr. Roger Seheult 58:12 Yeah.

Andrew Huberman 58:13 One, um, it's hard to a- a- attach a single number to this, but, uh, what fraction of the obesity epidemic that we observe in the United States do you think, um, is caused by altered interactions with sunlight or, you know, artificial light and its consequences? Or put differently, let- let me put it, let me phrase the question differently.

Dr. Roger Seheult 58:36 Yeah.

Andrew Huberman 58:37 If this were, if we were designing an experiment and I wanted to wager the hypothesis that exposure to 15 minutes a day of sunlight could help reduce, um, you know, adipose tissue, et cetera, independent of caloric intake, I know this is a, kind of a h- heretical idea-

Dr. Roger Seheult 58:57 Yeah.

Andrew Huberman 58:57 ... independent of additional exercise and all that, and I designed the experiment with you and we said, "Okay, people are going to go outside for 15 minutes a day. They're going to wear short sleeves if they can, or just simple long-sleeve clothing. They're going to get this long wavelength light from the sun 15 minutes a day."

Dr. Roger Seheult 59:12 Yeah.

Andrew Huberman 59:12 Based on what you told us about the- the light shown on the back and the-

Dr. Roger Seheult 59:16 Yes.

Andrew Huberman 59:16 ... lower glucose response-

Dr. Roger Seheult 59:17 Yes.

Andrew Huberman 59:18 ... independent of all other variables, what percentage improvement in, um, uh, sort of the overall metrics of obesity and metabolic d- disease do you think we- w- y- you would predict? If we were just going to, you know, we bet a sushi dinner, for instance.

Dr. Roger Seheult 59:33 Yes. Yeah, yeah.

Andrew Huberman 59:34 You know?

Dr. Roger Seheult 59:35 I guess another way of asking the question is, is at what level would I be really su- if it was 50%, I would be surprised.

Andrew Huberman 59:40 Right. Same.

Dr. Roger Seheult 59:41 Yeah. If it was 20 to 30%, I think that would probably be where it is, but that's significant.

Andrew Huberman 59:46 That's still significant.

Dr. Roger Seheult 59:47 Yeah.

Andrew Huberman 59:47 Okay, so

Andrew Huberman 59:48 that's- that's very helpful.

Dr. Roger Seheult 59:49 Yeah.

Andrew Huberman 59:49 Um, I think a lot of people hearing about the role of s- sunlight and long wavelength light in particular, its potential influence on improving overall immune system function, metabolic health, et cetera, might think that this sounds a little bit kind of biohacky because the moment we get into red lights, that sort of, like cold plunges, it's kind of, uh, immediately associated with kind of-

Dr. Roger Seheult 1:00:11 Yeah.

Andrew Huberman 1:00:11 ... uh, biohacking. People say it's bro science, this kind of thing. I just wanted to remind people that in the early 1900s, a Nobel Prize was given for the use of phototherapy, which is what we're describing, for the treatment of lupus. So the idea that, um, that specific wavelengths of light can be used in order to treat cellular health or offset, uh, cellular disease is not a new idea at all. And you mentioned this earlier, but I just wanted to underscore that for people.

Dr. Roger Seheult 1:00:38 Yeah.

Andrew Huberman 1:00:38 Um, the other way of looking at all this is that it's- it's primitive. So p- some people will say, "Oh, this is biohacking," right? Other people will say, "Well, this is just primitive. Like, get sunlight, of course."

Dr. Roger Seheult 1:00:47 Yeah.

Andrew Huberman 1:00:47 But you- you made a very key point, which is that the way we interact with light, and i- in particular with sunlight nowadays, is so disrupted compared to how it was just 10, 15, especially 20 years ago-I would just encourage people to pay attention for one week to how much time you're actually getting outside. Now, a few people will already be getting a lot of time outside, but just pay attention. How much time each day do you actually get outside-

Dr. Roger Seheult 1:01:14 Yeah.

Andrew Huberman 1:01:15 ... without sunglasses on?

Dr. Roger Seheult 1:01:17 Mm-hmm.

Andrew Huberman 1:01:17 And just measure your total exposure to outdoor time-

Dr. Roger Seheult 1:01:21 Yeah.

Andrew Huberman 1:01:22 ... let alone sunlight. I, I think that's just an important experiment for people to do. And because when one does that, you start to realize, "My goodness, I'm hardly getting outside at all."

Dr. Roger Seheult 1:01:29 Yeah. There was a study that was done, uh, looking at just this, except they actually used watches-

Andrew Huberman 1:01:34 Mm-hmm.

Dr. Roger Seheult 1:01:35 ... that, uh, was able to detect how much light. And it wasn't infrared light, but just total light. And the, the name of the, the study was basically, you know, dark days and bright nights.

Andrew Huberman 1:01:45 Mm-hmm.

Dr. Roger Seheult 1:01:45 And, and that is associated with higher mortality. We know, of course, about bright nights not being good, so not having a dark room to sleep in. These are things that can impair melatonin. That's associated with all sorts of gr- of bad things. But the dark days was something that, um, we really had not, uh, seen. And it was very interesting. They actually could show by the hour that if you were having light coming in, exactly what that did to your mortality. And mortality went up dramatically as you were still in, in daylight about, uh, midnight. But, uh, right around 7:00 in the morning, 8:00 in the morning, if you were out there and you're getting light now, instead of, uh, light being a liability, it was now a benefit.

Andrew Huberman 1:02:26 Incredible.

Dr. Roger Seheult 1:02:27 And it dropped dramatically.

Andrew Huberman 1:02:28 I also want to point out that when it's raining out-

Dr. Roger Seheult 1:02:32 Yeah.

Andrew Huberman 1:02:32 ... or when it's very cold out, even when it's dark and cloudy, quote unquote "dark and cloudy," there's far more photons coming through the cloud cover during the day than at night. People... I can't tell you, if I had a dollar for every time somebody said to me online and in person, "There's no sunlight where I live."

Dr. Roger Seheult 1:02:49 Exactly.

Andrew Huberman 1:02:49 Listen, go outside on the shortest day of the year.

Dr. Roger Seheult 1:02:53 Yeah.

Andrew Huberman 1:02:53 Go outside, folks, and look at how bright it is at 10:00 AM or even 2:00 PM.

Dr. Roger Seheult 1:03:01 Yep.

Andrew Huberman 1:03:02 Compare that to the middle of the night. There is sunlight.

Dr. Roger Seheult 1:03:05 (laughs)

Andrew Huberman 1:03:05 Unless you live in a cave, there's sun- sunlight all year round. It's just, it's just striking. So this morning, you know, it's, uh, for Southern California, it's pretty overcast today. It's, it's a misty rain, a little bit more. And I didn't want to go outside and get my sunlight this morning, but I know I was going to be in studio all day. And so I went downstairs, and I put on a beanie cap and a hoodie, and I just got outside with no sunglasses and, um, got some sunlight in my eyes. (laughs)

Dr. Roger Seheult 1:03:28 Yeah.

Andrew Huberman 1:03:28 You know, it's, it's really bright outside even when it's raining.

Dr. Roger Seheult 1:03:32 Yeah.

Andrew Huberman 1:03:32 It's really bright outside even when it's storming. And I think people somehow, they think that if it's not a clear sunny day, there's no sunlight to be had.

Dr. Roger Seheult 1:03:40 Correct.

Andrew Huberman 1:03:41 And, uh, there are many th- uh, gems that you're providing us today. But one key takeaw- takeaway is I want people to understand there is sunlight all year round.

Dr. Roger Seheult 1:03:48 Yeah.

Andrew Huberman 1:03:49 I, um... Yes, unless you live truly a subterranean life, that you are underground, there is sunlight during the daytime.

Dr. Roger Seheult 1:03:57 And if th- Yeah, and if there is, we have to work on that. Um, g- to your point about it being primitive, you know, um, I, I was looking at the history of this, and that was actually very interesting to me. You know, we used to have, uh, tuberculosis sanitariums at very high altitude, and part of that treatment was getting out into the, the sun. At very high altitude, you have less atmosphere, more ultraviolet light coming in, more light in general coming in. And when I started to look at this, I, I found it was very interesting what people started to say and what, what these people were actually saying at the time about sunlight. Um, you know, in terms of these, these people, these physicians and these healthcare providers back in the 1800s, they didn't have all of the scientific accoutrements that we have today. They didn't have X-rays and things of that nature. But one thing that they were very, very good at, probably better than we are good at, is their power of observation. They, they were able to get a stethoscope, put it on the chest, listen to the, the space between the second heart sound and the opening snap, and be able to say, "This person's got severe mitral stenosis. This is the one you need to operate on."

Andrew Huberman 1:04:57 Wow.

Dr. Roger Seheult 1:04:57 And they would do that. And, and sure enough, when they opened it up, sure enough, this is the one that had... You know. So the, the power of observation was probably better back in the 1800s. So w- what do you have? You have people like Florence Nightingale, who is the, the founder of modern nursing. And she was there, uh, you know, in, um, uh... There during the, uh, the Crimean War, taking care of British, uh, soldiers. And she wrote down... I- I'm paraphrasing basically what she said. She said, "Look, when it comes to treating the whole patient, the one thing that more than anything else is beneficial for these, these soldiers to recover is fresh air." "But," she said, "a very close second is direct sunlight, getting them out into sunshine, getting them arou- out into, into direct sunlight." Um, when I was looking at the S- the Smithsonian Institute a couple years ago, a few years ago, put out their top 100 most influential Americans of all time. Well, one of them was this lady. She's, she's the most translated female author in, in the world. Her name is Ellen G. White, and she had a third-grade education, but she was also very interested in health, health reform. And she wrote at that time in the 1800s that we ought to be getting out into the sunlight, that that's makes a big difference. Interestingly, something else that she said that I found really amazing, and this is... They're writing this before we understand circadian rhythm, before we understand melatonin. She wrote down, she's like, "Hey, this idea of keeping the lights on after, after 9:00, it's a wretched health-destroying habit. Every light should be extinguished," she said, "after 9:00." So I, I know about her sayings a little bit because she was the, the founder of, uh, Loma Linda University, which is where I went to school. So but, uh, just... We had this knowledge. Uh, as you said, we, we had hospitals that were designed specifically to get people out of the hospital and into the sunlight. Uh, you could see the architecture was designed for this. Why don't we do this today? I think we ought to, but I, I kind of have the sense... You asked the question, why don't we do this today?I have patients that I take care of, now that I understand this... Uh, I have patients that I have in the intensive care unit that I want to get outside in the sunlight. I actually try to get them out. It's difficult to do. These people are critical. Um, the people that we admit to the hospitals today are far sicker than the people that we admitted to sanitariums and, and hospitals in the 1800s. You have to make sure that they don't desaturate. You've got to take the oxygen tank out there with them. You've got to make sure that they don't have a code. I mean, you're outside, right? So you're outside of the, the, the bowels of the hospital where your support system is. It's a little bit of a risk to get those patients out there. N- nevertheless, I've convinced, um, some of my, uh, hospital staff to do that. And I've, I've had a number of success stories where we've had patients that were ready to be intubated, and we, we got them outside in the sunlight and they steadily improved dramatically after days of getting worse. And, uh, and they got better. There was a, a lady that actually contacted me. Her name is Amy Honmyhr, Eh, H-O-N-M-Y-H-R, if you want to look her up. She's on social media. Her son... This is a really amazing story... Her son contract- basically, at the age of 15, got, uh, leukemia. Got put on chemotherapy. And this was in Minnesota. Fortunately, it was in the summertime, and he got admitted to the hospital with what they call neutropenic fever, very high fevers, very low white counts as a result of the chemotherapy. And his immune system was, was completely shot. And unfortunately, he developed a very severe fungal infection in his lung called mucor. Uh, it just basically eats up the lung, goes right to the blood vessels.

Andrew Huberman 1:08:40 Mm-hmm.

Dr. Roger Seheult 1:08:40 He got so bad that they... There was, there was only one solution that they had at the time, and that was to take out the, the left lung. So they took out the left lung, and he continued to get worse. The right lung became infected. He started to, to get worse, had higher fevers. They had a meeting with the family. 15 years old, completely with it, realizing that he's dying, and they have to tell him that he's dying. So they made him what they call no code or DNR. And, uh, the staff came to him, and, and you can imagine, and I've been in this position before, where you're trying to do everything you possibly can and you just... You can't do anything else. So they came to him, the 15-year-old, and they said, "You know, this is it. Do you have any basically last wishes?" And he... You know, Amy, uh, his mom told me that he, he'd like to play outside, so he told them, you know, without any knowledge about what we've just been talking about. He just... This is his dying wish. "Take me outside. Just, I just want to go outside." And, and you know that nursing staff will move heaven and earth to do something that the patient requests to do, uh, even though it's not going to, you know, benefit them. They still want... It's his dying wish, they're gonna do it. So they, they hooked up oxygen tanks. They, uh, they, they got this, this 15-year-old boy in a, in a hospital bed outside on BiPAP with oxygen tanks for five hours a day. Um, his mom was telling me they were also g- uh, using something called a Firefly device, where they were just basically shining a light onto him to see if it would work. You know how this story ends. He did not die in two days like they told him. He got better. His fever went away. His oxygen requirements came down. A- and I'm not telling you this as a, as a, as "proof" that this is what happens, but you have to realize that he was in the hospital for six weeks under lea- underneath, you know, LED lighting. And as soon as he got outside, fever went away. And make a long story short, after five days, he came back inside, they repeated the CT scan. And she sent me the CT scans. I've seen them. We actually did a, a little thing on our, our MedCram channel on it. And, um, it w- the disease was almost gone. Uh, there's no explanation. To this day, they don't have an explanation.

Andrew Huberman 1:10:54 He's still alive today?

Dr. Roger Seheult 1:10:55 He's still alive. He's getting chemotherapy.

Andrew Huberman 1:10:57 Fantastic. Mm-hmm.

Dr. Roger Seheult 1:10:58 He, he went from basically... And, and of course, he, he's missing a lung, but he still has that lung. He's on... He's getting the, the antifungal medication. There's no sign of the fungus anywhere. So this is an anecdotal story. It doesn't prove anything, and I don't, I don't, I don't present it as proof. The things that I present as proof is randomized controlled trials, epidemiological trials with, with, uh, dose response curves. These are things that we can actually show the science with. The reason why I bring it up is because it shows what is it that we would need to do to get this type of treatment. It's, it's not easy to do, but if there is a will, there's a way to do it.

Andrew Huberman 1:11:34 I'd like to take a quick break and acknowledge one of our sponsors, Function. Last year, I became a Function member after searching for the most comprehensive approach to lab testing. Function provides over 100 advanced lab tests that give you a key snapshot of your entire bodily health. This snapshot offers you with insights on your heart health, hormone health, immune functioning, nutrient levels, and much more. They've also recently added tests for toxins such as BPA exposure from harmful plastics and tests for PFASs or forever chemicals. Function not only provides testing of over 100 biomarkers key to your physical and mental health, but it also analyzes these results and provides insights from top doctors who are expert in the relevant areas. For example, in one of my first tests with Function, I learned that I had elevated levels of mercury in my blood. Function not only helped me detect that, but offered insights into how best to reduce my mercury levels, which included limiting my tuna consumption... I'd been eating a lot of tuna... while also making an effort to eat more leafy greens and supplementing with NAC and acetylcysteine, both of which can support glutathione production and detoxification. And I should say, by taking a second Function test, that approach worked. Comprehensive blood testing is vitally important. There's so many things related to your mental and physical health that can only be detected in a blood test. The problem is, blood testing has always been very expensive and complicated. In contrast, I've been super impressed by Function's simplicity and at the level of cost. It is very affordable. As a consequence, I decided to join their scientific advisory board, and I'm thrilled that they're sponsoring the podcast. If you'd like to try Function, you can go to functionhealth.com/huberman. Function currently has a wait list of over 250,000 people, but they're offering early access to Huberman podcast listeners. Again, that's functionhealth.com/huberman to get early access to Function.It's

Andrew Huberman 1:13:22 a spectacular story, um, by any account. Um, I wanted to just touch on the fact that there's no replacement for sunlight. Getting patients outside is hard.

Dr. Roger Seheult 1:13:36 Yeah.

Andrew Huberman 1:13:37 Um, and at the same time, most people listening to this aren't... fortunately are not patients.

Dr. Roger Seheult 1:13:42 Right.

Andrew Huberman 1:13:42 Uh, um, thank goodness. Many people, however, have relatives or themselves are elderly. Um, as people get older, they tend to slow down, get outside less. There are many, uh, fortunate, uh, exceptions to this. But one of the setups that I created for myself, um, that I think is certainly feasible for a lot of people is the following. Uh, well, first of all, I always make it a point to get outside and get sunlight in my eyes.

Dr. Roger Seheult 1:14:11 (laughs) Yeah.

Andrew Huberman 1:14:11 Rain or shine.

Dr. Roger Seheult 1:14:12 Right.

Andrew Huberman 1:14:12 Um, and regardless of where I'm traveling and, uh, et cetera, I do that every single day. If I miss a day, it's only because of something like a, like a flight where I happen to be on a plane at the time of, you know, sunrise or something like that.

Dr. Roger Seheult 1:14:25 Yeah.

Andrew Huberman 1:14:25 In any case.

Dr. Roger Seheult 1:14:26 Yeah.

Andrew Huberman 1:14:26 But I have a setup that I, um, constructed for myself that is basically a 10,000 lux light. These are available, I don't have any relationship to 10,000 lux light sources. Um, those 10,000 lux light sources tend to be short wavelength shifted. They tend to be very blue. They're white light, but I don't think they have power across the visible spectrum. I think they're, they're very... A red light and infrared diminished. They tend to be, um, very blue and green light enriched.

Dr. Roger Seheult 1:14:55 Yeah.

Andrew Huberman 1:14:55 And it shows up as very bright white light. So, that's what, um, I put in front of me when I first wake up if the sun isn't out yet. But now I've started, um, putting a red light, near-infrared light next to it, and I'll spend the first couple minutes of my day, um, usually as I journal or do something like that, or sometimes just with my eyes closed, just pleasantly, you know, uh, facing in the direction of the 10,000 lux white light and the red light, near-infrared light. And I must say, um, again, this is anecdotal, but the, the combination of the two, not only does it wak- certainly wake you up, the white light will do that alone.

Dr. Roger Seheult 1:15:31 Yeah.

Andrew Huberman 1:15:31 Uh, we know the biological basis for that.

Dr. Roger Seheult 1:15:33 Yeah.

Andrew Huberman 1:15:34 But I, I have noticed a, a tremendous improvement in energy, mood, focus, et cetera, that comes from the addition of this red light, near-infrared light. This is not an advertisement for red light, near-infrared light.

Dr. Roger Seheult 1:15:45 (laughs)

Andrew Huberman 1:15:46 I, I promise. Uh, although, you know, I... This podcast does have a relationship to medical-grade red light devices, I, I... But I mention this because what I'm trying to simulate there is sunlight, but I still get outside and get sunlight. So, I just mention this setup because it seems to me that hospitals should be able to create this setup. It's for a minimum of cost. Certainly less cost than it takes to maintain a patient for one day.

Dr. Roger Seheult 1:16:10 Exactly.

Andrew Huberman 1:16:11 Like, I mean, the cost of maintaining a patient in, uh, for inpatient, uh, care is so high. Medical staff, the-

Dr. Roger Seheult 1:16:18 Yeah.

Andrew Huberman 1:16:18 ... the disposables, the dis- the, the disp- the, um, actual disposing of the disposables, the janitorial staff, the cafeteria... Like, I mean, hospital costs are, are outrageously high. Now, of course, people will hear this and think, "Well, that's exactly what hospitals want," right? Like, they can charge... The longer you stay, it's like a hotel. The longer that you stay, the longer they can charge you or your insurance. And I'm not a conspiracy theory type.

Dr. Roger Seheult 1:16:39 Yeah.

Andrew Huberman 1:16:40 But it, it is interesting that for many people, they associate going to a hospital with staying a long time and, and getting sicker. Sometimes they get better and go home, thank goodness.

Dr. Roger Seheult 1:16:49 Yes.

Andrew Huberman 1:16:49 You're a, certainly a well-meaning doctor. The nursing staff are well-meaning people.

Dr. Roger Seheult 1:16:53 Yes.

Andrew Huberman 1:16:55 Put simply, why don't hospitals include light therapy given the abundance of data on circadian rhythms and light therapy? And I'll just attach one more thing. My audience always gets upset at the duration of these, these questions/editorials-

Dr. Roger Seheult 1:17:09 (laughs)

Andrew Huberman 1:17:09 ... but this is my wheelhouse, this whole light thing. So-

Dr. Roger Seheult 1:17:12 Yeah.

Andrew Huberman 1:17:12 ... I can't help myself. There's also something known as ICU psychosis-

Dr. Roger Seheult 1:17:16 Absolutely.

Andrew Huberman 1:17:16 ... which is when people who are perfectly mentally healthy go into a hospital-

Dr. Roger Seheult 1:17:20 Yeah.

Andrew Huberman 1:17:20 ... because of the relationship to light and the disruption in circadian rhythm from the overhead lights, the checking of the patient in the middle of the night, the disruption in sleep, et cetera, people literally develop psychosis-

Dr. Roger Seheult 1:17:30 Yeah.

Andrew Huberman 1:17:30 ... that resolves itself the moment they get home and get onto a normal schedule. And it's well-known that the patients that are in a hospital bed next to a window don't experience this to the same degree, if at all.

Dr. Roger Seheult 1:17:44 No.

Andrew Huberman 1:17:44 So, it's, it's sort of like-

Dr. Roger Seheult 1:17:45 Yeah.

Andrew Huberman 1:17:45 I feel like we're, we're in an... We're sitting under an avalanche, not a waterfall, but an avalanche of data telling us what we need to do. And like, f- f- forgive me, but like, "What the hell is going on?"

Dr. Roger Seheult 1:17:54 Exactly. So, I, I can tell you that not only do you have less likely to get, uh, this type of ICU psychosis, but the data actually shows that people who are in a two-bedroom that are next to the window actually discharge from the hospital faster. And you say, "Ah, well, maybe that's the reason." Well, it's interesting because the financial incentives with hospitals is not monolithic. Some hospitals, uh, and their relationship to the insurance companies are at a situation where when a patient comes into the hospital and the, and the physician diagnoses them, the insurance will pay the hospital a certain amount of money for that diagnosis, and that's that. And also, there's, uh, something called subcapitative, uh, arrangements, where the hospital has a contract with an insurance company to take care of 30,000 people per member per month. And if that patient gets admitted to the hospital, that hospital has to take care of that patient, whatever the costs are. So, it, it basically takes the risk now and puts it from the insurance company onto the healthcare provider. So, in those situations, you'll see a hospital having a, uh, an army of case managers. They come down every day, "What are we doing for this patient? What do we need to do to get this patient out of the hospital?" So, they're motivated to get people out. And so when I say that, I'm even more bewildered than when you said at the beginning, "Well, if we have good data that shows that light therapy and light, getting people out into the sun actually can improve the discharge..." We, we had that, as I said, that study from Brazil-... where there was a randomized controlled trial, and they used 15 minutes of th- They actually made this jacket that they put on the patients, and they flipped it on with some patients, and they didn't flip it on with others.

Andrew Huberman 1:19:40 The, the, the jacket was a light jacket?

Dr. Roger Seheult 1:19:42 It was an LED jacket that was giving light out at 940 nanometers, infrared light. So you can't even tell if it's on. And as I said, the, the, the milliwatts per square centimeter was, like, 2.9. So you wouldn't even feel it. But yet, these patients, when they were done, seven days, 15