Dr. Andrew Huberman: How Cortisol Rhythm Prevents Burnout

1. 0:00 – 1:29

   Cortisol

   1. AHAndrew Huberman0:00

      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. Today we are discussing cortisol, in particular how to control your cortisol in order to avoid burnout or, should you already be feeling burnt out, how to overcome burnout. Now, it's hard for me to overemphasize just how important cortisol is. In fact, in the late stages of preparing for this episode, it dawned on me that if ever there were an episode of the Huberman Lab podcast that people could benefit from in terms of their health and well-being, this would be that episode. And I say that because as you'll soon learn, cortisol, the biology of it, how it impacts your mood, your sleep, your immune system, your overall feelings of well-being not just in the moment but over the long term, and your ability to control cortisol at different portions of the day and night makes it one of the most, if not the most powerful levers for your health and well-being. So I'm very excited to get into the material for today's discussion about cortisol, how to control it, and how to avoid and overcome burnout. 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, today's episode does include sponsors.

2. 1:29 – 3:16

   Stress, Tool: Daily Cortisol Rhythm

   1. AHAndrew Huberman1:29

      Okay, letes discuss cortisol. Now, I believe that most people have heard of cortisol, and most everyone that hears the word "cortisol" hears it somewhere nearby the word "stress." And it makes sense why you would hear about cortisol in that context, because indeed cortisol is a hormone that's made and released in response to stress. Now, the problem with thinking about cortisol simply as a stress hormone is that it's doing a lot of other things unrelated to stress that are super important and positive for you. However, it all depends on how high your cortisol levels are and when. So during today's discussion there's going to be a very prominent theme which is your cortisol rhythm, or more particularly, your 24-hour so-called circadian rhythm in cortisol. And here's the important first thing to remember: You want your cortisol high early in the day shortly after waking, and you want your cortisol low in the hours right before sleep and in the first hours of sleep. If you remember nothing else from this episode, please remember that, because if you get those two things correct, everything else in terms of health and wellness and performance, all of that will be reinforced by getting your cortisol rhythm correct. So today I will explain how to get your cortisol rhythm correct. I will also explain what stress does to cortisol in the short term, which turns out to be good for you, and in the long term if you're dealing with long bouts of stress associated with what eventually becomes burnout. So it's also important for me to point out that if you're already feeling wired and tired and burnt out, if you don't have energy in the morning or if you somehow have low energy all day but then at night you can't sleep, this is very typical of burnout, or if you have morning anxiety, literally all of that can be resolved, perhaps not entirely but mostly and in some cases entirely, by fixing your cortisol rhythm.

3. 3:16 – 6:39

   Cortisol & Directing Energy, Glucose, Adrenals

   1. AHAndrew Huberman3:16

      Okay, so to understand and control your cortisol, the first thing you really need to know is that cortisol, again, is not a stress hormone per se, rather cortisol is involved in deploying and directing energy to tissues that need it most. Okay? I'll say that again. Cortisol is not a stress hormone per se. Cortisol should be thought of as a hormone that causes the deployment of energy into the body and helps direct that energy to particular tissues, especially your brain, in order to deal with, yes, stressors but all sorts of other things that demand your energy. So, the way to think about cortisol is that it causes the release of glucose, blood sugar, into the bloodstream, and it does that by controlling energy released from the liver and from the muscles, but cortisol is not made in the brain. Cortisol is made in your adrenal glands, and of course the adrenals are associated with adrenaline, also called epinephrine. Those are the same thing, by the way, epinephrine and adrenaline. And your adrenals will release epinephrine, aka adrenaline, in response to a stressor very quickly. Your adrenals can also release cortisol in response to a stressor, but it needs to make that cortisol first and then release it. So cortisol acts on a slightly slower time scale to deal with stress, and as I mentioned before, cortisol isn't just about stress. Cortisol is also about generating energy to deal with pretty much anything that requires (laughs) energy. So, when you need energy to deal with stress, to deal with getting out of bed in the morning, to deal with a hard school task, work task, relationship task, drive your kids to school, whatever, cortisol needs to be released. Okay? This is a very different mental framework around cortisol than we're used to hearing. We normally hear "elevated cortisol," "I'm releasing cortisol," "My cortisol is too high." You need cortisol released in order to get glucose, blood sugar, into the bloodstream. Now, cortisol is unique compared to, say, adrenaline or norepinephrine because cortisol is what's called lipophilic, meaning because cell membranes are lipid, fat, and cortisol is lipophilic, it can move through cell membranes, and what that means in the functional context, what it means for you, is that cortisol is released from the adrenals, circulates in the blood, just like adrenaline would, but unlike adrenaline, it can cross the blood-brain barrier, and it really likes to do that because there are a lot of receptors for cortisol in the brain, in particular in a region of the brain called the hippocampus which is involved in memory. Now, we'll come back to the hippocampus later because the hippocampus is vital for understanding what happens during situations of chronic stress and why cortisol can be dysregulated under conditions of chronic stress, but for the time being, let's go back to thinking about cortisol simply as a mode of releasing glucose into the bloodstream.Cortisol releases glucose into the bloodstream. Much of that glucose is going to be directed toward brain energy so that neurons, nerve cells can use it to think and to deal with whatever happens to be confronting you during your day, good or bad, stressful or non-stressful. So one of my biggest wishes for today is that you and hopefully the rest of the world will eventually come to adopt the understanding that cortisol is not a stress hormone. Yes, cortisol is involved in stress, but cortisol's main job is to deploy energy. It's an energy-producing hormone, in particular a brain energy-producing hormone.

4. 6:39 – 10:14

   Sponsors: Carbon & BetterHelp

   1. AHAndrew Huberman6:39

      I'd like to take a quick break and acknowledge one of our sponsors, Carbon. Carbon is a diet coaching app built by nutrition expert Dr. Layne Norton. Now, I've used Carbon for more than three years now, and I have to say, having been interested in fitness and my nutrition for more than three decades, it's among the most powerful tools for nutrition coaching and effective weight management that I've ever encountered, especially if your goal is like mine, which is to maintain or build muscle while also losing fat. Now, I'm turning 50 years old this September, and even though I consider myself in pretty good shape and I've been training for a long time and trying to eat right, one of my goals is to hit 50 in the absolute best shape of my life. To do that, I'm dialing in my nutrition using Carbon, with the goals of increasing my muscle mass, increasing my strength, while also decreasing my body fat. I've been raving about the Carbon app to friends and to family and to members of my Huberman Lab team over the last few years, and everyone who's joined me in using it has found it to be tremendously useful. In fact, some of those people are going to join me in my approaching 50 fitness goals and body composition goals. My birthday is September 26th, and so I'd like to invite you to join if you would like to improve your body composition and fitness, to also use the Carbon app. Now, there are a lot of apps out there that are focused on fitness and nutrition. But what makes Carbon different is that it doesn't just hand you a one-size-fits-all plan. It actually learns your metabolism over time, and it adapts your program based on your results. It also allows you total flexibility in how you eat. If you're plant-based or you're keto, high carb, low carb, anything in between, or even if you switch back and forth between different diets, Carbon works around your preferences. The other thing I love about Carbon is that it easily adapts to whether you're the type of person who likes to put in the specific brand and the exact number of ounces or grams of food that you ate or if you tend to be a little bit looser about that, like you ate half a handful of almonds or something like that. It can learn and adapt to that and still give you accurate recommendations. So if you're looking to take a smarter, more personalized approach to your nutrition, I can't recommend the Carbon app enough. To try Carbon, you can go to joincarbon.com/huberman. While Carbon does not typically offer trials or promotions, they've agreed to give a free seven-day trial to all Huberman Podcast listeners. Again, that's joincarbon.com/huberman to get a seven-day free trial. Today's episode is also brought to us by BetterHelp. BetterHelp offers professional therapy with a licensed therapist carried out entirely online. I personally have been doing therapy for well over 35 years. I find it to be an extremely important component to overall health. In fact, I consider doing regular therapy just as important as getting regular exercise, including cardiovascular exercise and resistance training, which of course I also do every week. There are essentially three things that make up great therapy. First of all, it provides the opportunity to have a really good rapport with somebody that you can really trust and talk to about essentially any issue that you want. Second of all, it can provide support in the form of emotional support or directed guidance, or of course both. And third, expert therapy should provide you useful insights, insights that can help you improve in your work life, your relationships, and in your relationship with yourself. With BetterHelp, they make it very easy for you to find an expert therapist who you resonate with and that can provide those three benefits that come from expert therapy. Also, because BetterHelp therapy is done entirely online, it's very time efficient and easy to fit into a busy schedule. There's no commuting to a therapist's office or sitting in a waiting room looking for parking, any of that. You just hop online and you do your session. If you'd like to try BetterHelp, you can go to betterhelp.com/huberman to get 10% off your first month. Again, that's betterhelp.com/huberman. Okay, so

5. 10:14 – 17:55

   Daily Cortisol Phases & Rhythm, Waking Up & Cortisol

   1. AHAndrew Huberman10:14

      just a couple of minutes ago, we were talking about how cortisol needs to be high in the morning shortly after waking and low in the nighttime, and certainly while you're asleep. Except for, as it turns out, in the final hours of sleep. You actually want your cortisol rising. So we need to take a step back and ask, "Why is cortisol released? When is it released? How is it released?" Because understanding that gives us control over cortisol at any time of day or night. So rather than just list off a bunch of things that you can do to increase your cortisol or decrease your cortisol, which I'd love to do, frankly, but the problem with that is if I do that, it doesn't take into account that your levels of cortisol are constantly changing across the 24-hour cycle. So if you don't understand that endogenous 24-hour rhythm in cortisol, not just knowing that it's high in the morning and lower at night, if you don't understand how that's regulated, you won't know which protocols, which tools to apply when. But if you can understand how that rhythm is generated and how cortisol is released in response to short-term events like stress, but also the desire or need to exercise, the desire or need to focus, if you can understand those things, how cortisol is released in the short term and across the 24-hour cycle, how it literally regulates itself, then you will have immense control over cortisol across the 24-hour cycle from day to day and from moment to moment. Okay, cortisol is a corticosteroid hormone. Yes, it's a steroid hormone, just like testosterone's a steroid hormone, just like estrogen's a steroid hormone. Steroid hormones are derived from the molecule cholesterol, and there are a bunch of biochemical steps that take you from cholesterol to cortisol or from cholesterol to testosterone or from cholesterol to estrogen. Scientists have long known that cortisol is not at the same level throughout the 24-hour day. In fact, there's a...... quite classic study now that examined the 24-hour pattern of the episodic secretion of cortisol in normal subjects. And what they found is that there are essentially four phases of cortisol levels. I'll just read off what these different phases are. Phase one is a six-hour period of what they call the minimal secretory activity, meaning when cortisol is not released very much. That starts four hours before and continues until two hours after lights out for sleep. Okay? Four, starts four hours before and continues until two hours after you turn your lights out to go to sleep. The second phase of cortisol, in which the levels are quite different than in the first phase, is a three-hour period which they called the preliminary nocturnal secretory episode, but we can simply call the third to fifth hour of sleep. So in your third to fifth hour of sleep, you have a second phase, and this phase they call the preliminary nocturnal secretory episode, and this is when cortisol is slightly starting to rise, just a little bit. In the first phase, cortisol is very, very low, or ideally, you want cortisol very low. So this is under normal, healthy conditions in that first phase, the four hours before until the two hours after lights out. Cortisol is going to be very low, and it's going to stay low, and then in the second phase, it's going to slightly rise into the third and fifth hour of sleep. Then in phase three, which here is listed as a four-hour period, but the exact duration's going to vary, you have what's called the main secretory phase of cortisol. This is when cortisol is increasing very, very fast, and this occurs, believe it or not, during the sixth, seventh, and eighth hour of sleep. Now, you might say, "I only sleep six hours, so do I get that fast rise in cortisol?" Guess what? You don't. If you sleep seven hours, you only get a portion of that fast rise in cortisol. If you sleep eight hours, you get the full duration, and if you sleep nine hours, yes, your cortisol will continue to rise. So the idea here is that in the very final hours of sleep, your cortisol is starting to rise quickly. This is the time of sleep that correlates with when REM sleep, rapid eye movement sleep, is most abundant. Okay? So in the early part of your sleep night, slow wave deep sleep is most abundant. This is when growth hormone is released. This is when your metabolism tends to be very low. Think about it. Metabolism low means low requirement for blood glucose, and it's associated with low cortisol levels. Starting to make sense. In the last portion of sleep, the final, say, two to three, or if you sleep nine hours, four hours of sleep, you have rising levels in cortisol. We know that's associated with REM sleep, rapid eye movement sleep, and we know that REM sleep is a time of robust brain activity that even is greater than what occurs during wakeful states. What do you need for robust brain activity? You need energy. Where's that energy coming from? Blood glucose. How is that blood glucose deployed? Because cortisol causes its deployment. Okay? Starting to make sense now? And then there's a fourth phase of secretory, what they call secretory activity of cortisol, which is after you wake up. Starts right after you wake up. And I'm going to add another little sub-phase to this, not to complicate it, but because it's a very powerful time each day, which is the first hour after waking. From the moment you open your eyes and you decide to get out of bed, doesn't matter if it's because of an alarm clock or it's because you just naturally woke up, that first hour is a very special hour, because it's a time in which you can further amplify the increase in cortisol. After that first hour, or certainly after about 90 minutes, you don't have that opportunity again until the next morning. There are things you can do to reduce your cortisol or to slow its decline into the afternoon and evening, but that first hour after waking is critical. Okay. So to step back now, what do we have? Let's talk about this in real world terms. In the hours right before falling asleep and in the first hours of sleep, your cortisol is very low, ideally. This is the ideal case scenario for health, uh, for your mental health, for your physical health, for performance. Then cortisol starts to rise on its own. You're not doing anything to make it rise. It starts to rise, in particular as you transition from the middle of the night toward the end of your sleep night, and then just before waking, your cortisol is sharply rising, steep, steep slope of increase. And then as you wake up, boom. You have this hour long or so opportunity to further increase your cortisol, and you definitely want to increase your cortisol further during that first hour. And then about three, four hours later, so for most people that would be late morning or around noontime, your cortisol levels are slowly going to start to decline. However, if they decline too slowly, that's bad. If they decline too sharply, that's also bad. So the picture I'm trying to draw for you here is you want a really sharp spike in cortisol as you arise in the morning, and then you want that to taper off somewhat gradually, so not too steeply, not too gradually, into the afternoon such that by three, four hours or so before sleep, your cortisol levels are low, low, low, low, low and continuing to fall lower before they start up again the next morning in anticipation of you waking up. And if you haven't already caught onto this yet, you literally wake up because of a rise in cortisol. It's called the cortisol awakening response, or CAR, C-A-R, cortisol awakening response. The importance of cortisol for waking up and for feeling alert early in the day cannot be overstated. This is the anchor point at which you have control over your cortisol levels, and if you do things right in that first hour or 90 minutes of the day, you're going to set yourself up for an overall healthy pattern of cortisol release at night as well. Okay, so stay

6. 17:55 – 24:57

   Cortisol Release & Regulation, Hypothalamic-Pituitary-Adrenal (HPA) Axis

   1. AHAndrew Huberman17:55

      with me here as we get into a bit of mechanism as to how this cortisol rhythm is generated, because if you can understand that, it gives you immense control. Okay, so let's talk about how cortisol is generated and how it self-regulates itself. So cortisol, again, is made and released from the adrenals, to be specific, from a particular middle layer of your adrenals where a particular category of cells that make cortisol reside. Those cells need the instruction to make and release cortisol, and that instruction comes in the form of a hormone.So, the whole story starts up in the brain in an area of the so-called hypothalamus. Hypothalamus is a, a little structure, it's actually quite small, about, the size of about two small marbles sitting above the roof of your mouth, and it, they sit next to this thing that we call a ventricle, which is where the cerebral spinal fluid circulates. Now, this turns out to be important because the cerebral spinal fluid gives the brain, or the neurons there, information about the chemistry of the body. It gives the neurons there information about what's in the bloodstream too because the, the area there allows blood vessels to get closer to the neurons and expose the neurons to more of what's going on in terms of the body chemistry than neurons located more deeply in the brain. So, it's nice that the neurons that we're gonna talk about now reside in an area of the hypothalamus called the paraventricular nucleus. Para means near, ventricular means ventricle, so paraventricular, near the ventricle, where they can access information about the body's chemistry. So there are neurons that reside in the so-called PVN, paraventricular nucleus, and they extend processes into the pituitary gland. The pituitary gland is a little stalk that has a couple of different lobes, okay? They literally look like little lobes. It looks like if you, uh, took a couple, uh, cloves of garlic and you held onto their stalks next to one another, those two, uh, cloves of garlic, a big stalk and a slightly smaller stalk, that's kind of what the pituitary looks like. And the pituitary actually extends out of the brain. And the neurons in the paraventricular nucleus release a hormone called corticotropin-releasing hormone, or CRH. Corticotropin-releasing hormone acts on neurons in the anterior pituitary, in that front piece of garlic, and causes the cells there to release a hormone called ACTH, adrenocorticotropin hormone, okay? I know there's an all, a lot of nomenclature here, but you should know the facts. ACTH is then released into the bloodstream and it travels down to the adrenals and it stimulates the release of cortisol, in fact, by binding to something called the melanocortin receptor, which doesn't seem important for the moment, but later when I tell you why people who have chronically elevated cortisol get a, what's called hyperpigmentation, they get some pigmentation on their face that's kind of blotchy, right? This is a symptom of something called Cushing syndrome, which is elevated cortisol. It will make sense. Melanocortin, okay? It's involved in pigmentation. The melanocortin receptor sits in that middle layer of the adrenals and ACTH binds to it, causing the synthesis and release of cortisol. Okay, then cortisol in response to stress, yes, but also in response to any time we need to get our energy going, our brain energy, our focus, or, as you learned a few moments ago, any time we need to wake up in the morning, all right? Any time we need to get out of bed. That requires energy, right? In fact, the transition from sleep to wakefulness is one of the biggest requirements for an energy surge, which is why you have the cortisol awakening response. So, cortisol is going to be released into the bloodstream. It's going to cause the deployment of blood glucose, the breakdown of amino acids and other fuels in muscle, in liver, in particular glycogen in the liver. That's going to be released into the bloodstream, and here's the thing. As cortisol is released into the bloodstream, the neurons in the brain that cause the release of CRH, corticotropin-releasing hormone, have access to how much cortisol is in the bloodstream. How? Well, they are paraventricular. Blood vessels and capillaries are also lining the ventricles. So those cells in the paraventricular nucleus have a sort of thermometer, if you will. They're kind of like a thermostat paying attention to just how high levels of cortisol are in the bloodstream. So when levels of cortisol in the bloodstream are very low, those cells in the paraventricular nucleus release more CRH to stimulate the release of ACTH to go to the adrenals to cause the stimulation and release of more cortisol, driving levels of cortisol up. And by the way, cortisol has a relatively long half-life, so it tends to accumulate in the bloodstream. So as levels of cortisol tend to go up, let's think about that last phase of sleep, maybe, you know, two or three hours before you wake up. Cortisol's going up, up, up, up, up, up. What ends up happening eventually is that the cells in the paraventricular nucleus of the hypothalamus that release CRH hit a point where they realize, at a biochemical level that is, they realize based on receptor saturation and some other mechanisms internal to the cells, ah, cortisol levels are really, really high right now. Let's shut down the release of corticotropin-releasing hormone, which causes a shutdown of the release of ACTH, which causes a shutdown of the synthesis and release of cortisol from the adrenals. So this is what we call a negative feedback loop. And by the way, this is the same way that testosterone works. In many ways, it's the same way that estrogen works, although estrogen's subject to a bit more regulation as well. When levels of the hormone cortisol reach a certain point, a certain threshold, it shuts down its own production by turning off the signals that would cause more of it to be produced. Okay? So this is a negative feedback loop. Now, that means that cortisol, after reaching a certain high level in the morning, will eventually start to drop off, and those levels will continue to drop off and should we encounter a need for a lot of brain energy, so it could be a really focused conversation, it could be an exam, it could be you're playing a bout of soccer or you're going to the gym and you need a bunch of energy, you have to rally your, your mind and your motivation to do that, yeah, you'll get an increase in cortisol. But that little increase in cortisol is like a bump of cortisol that rides on that already dropping endogenous rhythm in cortisol. So by now it's probably dawning on you that as those levels of cortisol get lower and lower into the late afternoon and evening, et cetera, those cells in the brain that release CRH are now registering at a biochemical level, at a cellular level, that the levels of cortisol are very low, and so eventually...Those levels get low enough that those cells in the paraventricular nucleus go, "Oh, well, cortisol levels are really, really low. They're not zero, but they're really low. Let's start releasing corticotropin-releasing hormone," which stimulates ACTH, which stimulates the adrenals, and that's why cortisol starts to rise again late in sleep and into the next morning. Does it make sense? Hopefully that makes sense. Cortisol is regulating its own production so that it doesn't get too high or too low, and it does that through a negative feedback loop involving the cells in the hypothalamus. So what

7. 24:57 – 28:42

   Rapid & Delayed Stress Response, HPA Axis

   1. AHAndrew Huberman24:57

      I just described was something called the HPA axis, hypothalamic, H, pituitary, P, adrenal axis. Okay? So the HPA axis is important for synthesis of cortisol to generate this 24-hour so-called circadian rhythm. It's also important for the synthesis of cortisol in response to stress, both short-term and long-term. And I'm going to get back to stress a little bit more later, but let's just for a moment think about that HPA axis and two things about stress that you can kind of put up on the shelf that will be helpful later as we get into our discussion about short-term and chronic stress. Stress activates the HPA axis, but as you know, stress is a very fast response, meaning when you encounter a stressor, your heart rate goes up. Your blood pressure goes up. Your eyes widen. Literally, your pupils widen, and your eyes widen, and all sorts of things happen in terms of your levels of alertness and attention. That very rapid response occurs also because of the HPA axis, but because of the release of adrenaline, epinephrine and norepinephrine from your adrenals and also from areas in your brain. That's a very fast thing. It happens within milliseconds, if not milliseconds, certainly within seconds. Just think about if you're walking down the street in a city and a, you know, a car kind of veers onto the sidewalk and you have to jump out of the way, you made the reaction without even basically having to think about it. You get out of the way, and your heart rate's up. Everything's happening all at once. You, you're completely different state than you were just a few seconds prior, even. That's all happening fast because of adrenaline and norepinephrine. Cortisol, yes, will be deployed in response to that sort of stressor, but cortisol needs to be synthesized and then released, and then it causes the release of glucose, and that's going to take some time. In fact, it takes about 10 minutes. So it turns out that can explain a lot of why stress tends to come on very quickly and last rather long relative to the stressor, to the thing, like the car that veered up onto the sidewalk. You probably had that experience where something happens that's very stressful. Then the stressor is resolved, right? The car didn't hit you. It didn't kill you, thank goodness. Didn't run over your leg. Didn't break your leg, thank goodness. But you turn to your friend, and you're like, "Oh, my goodness. Oh, yeah, that was a close call." And guess what? About five, 10 minutes later, you're still kind of stressed about it. Something stressful happened. Something real, as, as we say, happened, and it's hard to just kind of get back to baseline again, and that's because that wave of cortisol comes on a little bit later, and it lasts longer. It has a much longer half-life than does adrenaline or norepinephrine. So the stress response has this fast aspect to it that's generated through the HPA axis and through, again, release of hormones such as norepinephrine in the brain. Those two things happen in parallel. By the way, that happens because adrenaline is released from the adrenals very quickly to cause changes in the body, but adrenaline can't cross the blood-brain barrier, and when you need a very fast reaction in order to deal with a stressor, you can't really wait for that hormone to cross from the bloodstream into the brain, so you release norepinephrine from a site in the brain very quickly as well in parallel with that release of adrenaline. So those two things happen in parallel. Boom, you deal with the stressor. Hopefully that stressor is resolved, didn't injure you or worse, but then that wave of synthesis and release of cortisol occurs. Blood glucose is elevated, and so it takes a while for stress to come down again. All of that is mediated through the HPA, hypothalamic-pituitary-adrenal axis, as is the generation of that 24-hour rhythm in cortisol where cortisol slowly rises and then goes back down into the evening and nighttime and so on. Okay?

8. 28:42 – 36:58

   Bright Light & Cortisol Release, Tool: Increase Morning Cortisol & Sunlight

   1. AHAndrew Huberman28:42

      Now, that's the first way that cortisol is synthesized and released, but there's a second way that turns out to be very important, and it involves a structure called the suprachiasmatic nucleus, or SCN. The suprachiasmatic nucleus is your brain's central circadian pacemaker. It's the set of neurons also above the roof of your mouth, also in the hypothalamus, that basically orchestrates all the activities of all the organs and cells in your body like an orchestra conductor, makes sure that your gut cells are active at a certain time, that you're hungry at certain times, you're not hungry at others, regulates pretty much everything, including cortisol. And the SCN can control the HPA axis, when it's active, when it's less active, by virtue of connections that run through, if you really wanna know the names, for you aficionados, through the dorsomedial hypothalamus and then to the paraventricular nucleus. Okay, that's all fine and good. It just means that the HPA axis is subject to immediate control over stressors or other things that require our attention. Again, doesn't have to be stress, could be positive things. As well, the HPA axis is under the control of the SCN, circadian timing, which is what generates that high in the morning, low in the afternoon and evening rhythm, all of that subject to negative feedback. Controls itself, making sure levels don't get too high or too low for too long. But there's a second pathway, a parallel pathway, as we call it, that is separate from the HPA control over the synthesis and release of cortisol, and this one originates also in the SCN, the suprachiasmatic nucleus, and is relayed through a couple of different synapses, a couple of different junctions, and eventually runs through a nerve pathway that, for you aficionados, is called the splanchnic nerve, all right? Kind of cool name, splanchnic nerve.... that can cause the release of cortisol, or I should say the synthesis and release of cortisol in response to n- times when you want cortisol to be especially high for a while, okay? So this is different than the requirement for stress. You might think, "You know, we want cortisol to be high in response to stressors." No, your brain and body are really smart. They're really, really smart. When you encounter a stressor, you deploy just as much cortisol as your body thinks you might need in order to resolve that stressor and probably not a whole lot more, and because cortisol lasts a while, as we just discussed, it gives you an opportunity to have more brain energy, bodily energy to resolve that stressor. But your brain and body sort of know at a biological level that you don't want cortisol too high for too long. That's why you have the negative feedback loop. However, there's a beautiful mechanism, which is the second parallel pathway from the SCN, that allows you to control the amount of cortisol that you release and boost it even further for a long period of time. Now, when would you want that to occur? You think, like, "Why would I want that to- to occur?" Maybe in response to a chronic stressor, a very long stressor. Well, actually, you wouldn't want that to happen because if cortisol is elevated for too long at the wrong times of day or night, you run into all sorts of issues related to immune system suppression, to dysregulation of metabolic function, and this is where we start to hear about some of the more common negative aspects of chronically elevated cortisol, like accumulation of body fat around the midsection, the so-called moon face, you know, the, uh, literally the rounding of the face and the accu- accumulation of fat in the face. Uh, there's, uh, usually an accompanying loss of fat in the neck and accumulation of fat around the belly. Nobody wants this, right? Some things like hyperpigmentation and things like that. All right? But there is a time of day when everyone would benefit from having higher levels of cortisol not just for a few moments or minutes, but for several hours, and that's the first hour or two or two and a half or three after waking. So while there's this 24-hour rhythm in cortisol where cortisol is elevated in the morning, there's this unique opportunity of about an hour to two hours, maybe three immediately after waking when your SCN can activate this parallel pathway down to your adrenals to cause the release of more cortisol and elevate your morning energy, alertness, mood, and so on. Now, you might be saying, "Wait, this is kinda confusing. The SCN controls the 24-hour rhythm, but it's also controlling the faster release of cortisol during this, you know, kind of one unique window immediately after waking?" It's kinda confusing, right? The c- the SCN's involved in both things. Ah. Well, the SCN has access to one particular feature of your external world, of your environment that no other structure in the hypothalamus has access to, and that's the presence or absence of light. The retina, the light-sensing tissue at the back of your eye, contains a bunch of different neurons that sense light, convert it into electrical signals, and hand those electrical signals off to a certain class of cells called the retinal ganglion cells. Retinal ganglion cells project into the brain to allow you to see things, colors, shapes, motion, et cetera. However, there's a specialized subset of those retinal ganglion cells called the intrinsically photosensitive melanopsin retinal ganglion cells that respond in particular to very bright light or more accurately to transitions between dimmer environments and brighter environments that last a long period of time, like, for instance, when you go from your eyes closed in sleep to your eyes opening when awake. Those neurons project directly to the suprachiasmatic nucleus. In other words, your SCN has unique access to information about when the levels of overall luminance in your environment change dramatically, such as upon waking. So here's where I'm going to suggest a protocol, and you've heard this protocol before, I know. The protocol is to get bright light, ideally from sunlight, into your eyes within the first hour of waking, ideally within the first 30 minutes. Ideally, it's from sunlight, so you would go outside, take your sunglasses off. Eyeglasses and contacts are fine even if they have UV protection in them. Look in the direction of the sun. Blink as needed to protect your eyes. Yes, you can do this on cloudy days. In fact, it's more important to do on cloudy days because cloudy days tend to be dimmer overall, and this is a unique opportunity to boost your cortisol levels in that first hour of the day. If you don't have access to sunlight for whatever reason, travel, you live in a cave, time of year, weather, whatever, you could use a 10,000-lux artificial light. These are available online for usually about $100 or so. These are very useful tools. Some of them are portable. If you're going to do that, I still highly recommend that you get outside and get some sunlight in your eyes as soon as you can once the sun is out, but for you very early risers that wake up before the sun is out, this is so, so key. And I know I've been talking about this for years on this podcast and elsewhere, and I know I've just been, you know, hitting this like, like a, you know, banging on the same drum over and over again, but that additional surge in cortisol that can occur only in that first one to, say, two or three hours of the day, that's a very special time because it's not just about the elevated mood, focus, and alertness that you're going to achieve during that time by virtue of getting bright light in your eyes. It's also the case, and please hear this, I wanna highlight bold, underline this for you. It's also the case that the higher that first peak in cortisol is early in the day, the better you're setting yourself up for low levels of cortisol later in the evening and at night, which will allow you to fall asleep easily, to stay asleep easily. And now you know why. The reason why is that negative feedback regulation of cortisol. Think about it. If cortisol gets too high, the system shuts down the release of more cortisol, and what you've done by viewing bright light as soon as possible after waking is to amplify your levels of cortisol, which then are going to trigger that negative feedback loop and going to cause cortisol to gradually decline from the late morning, perhaps starting around, mm, 10:00 a.m., 11:00, noon, depending on when you woke up, of course.Dropping, dropping, dropping into the afternoon so you have plenty of energy into your early afternoon, late afternoon. But by evening and nighttime, your cortisol levels are low. I'd like to take

9. 36:58 – 39:48

   Sponsors: AG1 & David

   1. AHAndrew Huberman36:58

      a quick break and acknowledge our sponsor, AG1. AG1 is a vitamin mineral probiotic drink that also includes prebiotics and adaptogens. As somebody who's been involved in research science for almost three decades and in health and fitness for equally as long, I'm constantly looking for the best tools to improve my mental health, physical health, and performance. I discovered AG1 back in 2012, long before I ever had a podcast, and I've been taking it every day since. I find it improves all aspects of my health, my energy, my focus, and I simply feel much better when I take it. AG1 uses the highest quality ingredients in the right combinations, and they're constantly improving their formulas without increasing the cost. In fact, AG1 just launched their latest formula upgrade. This next-gen formula is based on exciting new research on the effects of probiotics on the gut microbiome, and it now includes several clinically studied probiotic strains shown to support both digestive health and immune system health, as well as to improve bowel regularity and to reduce bloating. Whenever I'm asked if I could take just one supplement, what that supplement would be, I always say, "AG1." If you'd like to try AG1, you can go to drinkag1.com/huberman. For a limited time, AG1 is giving away a free one-month supply of omega-3 fish oil along with a bottle of vitamin D3+K2. As I've highlighted before on this podcast, omega-3 fish oil and vitamin D3+K2 have been shown to help with everything from mood and brain health to heart health to healthy hormone status and much more. Again, that's drinkag1.com/huberman to get a free one-month supply of omega-3 fish oil plus a bottle of vitamin D3+K2 with your subscription. Today's episode is also brought to us by David. David makes a protein bar unlike any other. It has 28 grams of protein, only 150 calories, and zero grams of sugar. That's right, 28 grams of protein, and 75% of its calories come from protein. This is 50% higher than the next closest protein bar. David protein bars also taste amazing. Even the texture is amazing. My favorite bar is the chocolate chip cookie dough, but then again, I also like the new chocolate peanut butter flavor and the chocolate brownie flavor. Basically, I like all the flavors a lot. They're all incredibly delicious. In fact, the toughest challenge is knowing which ones to eat on which days and how many times per day. I limit myself to two per day, but I absolutely love them. With David, I'm able to get 28 grams of protein in the calories of a snack, which makes it easy to hit my protein goals of one gram of protein per pound of body weight per day, and it allows me to do so without ingesting too many calories. I'll eat a David protein bar most afternoons as a snack, and I always keep one with me when I'm out of the house or traveling. They're incredibly delicious, and given that they have 28 grams of protein, they're really satisfying for having just 150 calories. If you'd like to try David, you can go to davidprotein.com/huberman. Again, that's davidprotein.com/huberman. Now we're

10. 39:48 – 41:44

    Viewing Bright Light & Mood, Depression, Seasonal Affective Disorder (SAD)

    1. AHAndrew Huberman39:48

       going to talk about some other things that you can do to boost your morning cortisol in a meaningful way. However, before I do that, I have to say that this viewing morning sunlight thing, or bright light from a 10,000-lux artificial source, the increase in cortisol that it provides, and therefore the increase in energy and mood and focus, et cetera, is very significant. It's been shown to quickly increase cortisol levels by up to 50%, five-zero percent. And, in fact, it's clinically significant. People who live in areas of the world where during winter there's very little availability of sunlight and just rely on artificial indoor lights often suffer from what's called seasonal affective disorder. The protocol I just described is exactly the same protocol that they have used successfully to offset seasonal depression. Now, I realize that most of you listening to this don't live in areas of the world too close to the poles, so no doubt you get more sunlight available to you during the winter than you do if you were to, say, live in Scandinavia or down at the South Pole. However, these days, most people are not taking advantage of those early hours of the day to get outside and get bright light from sunlight or from a 10,000-lux artificial source. In fact, most people just look at their phone or flip on a few indoor artificial lights, and that is not going to be sufficient to boost your cortisol levels the way you need to in order to achieve the kind of elevation in mood, focus, and alertness, and that can offset things like not just seasonal depression, but mild depression, malaise, lack of daytime energy, and on and on. So this thing about viewing bright light early in the morning, it's a real thing from the standpoint of the mechanism is understood, the ideal timing is understood, the magnitude of the impact on cortisol is very significant, these are big effects, and it's clinically significant with respect to mood, meaning you're going to feel more energized. You're going to feel better. Okay,

11. 41:44 – 49:30

    Increase Morning Cortisol, Tools: Hydration, Delaying Caffeine Intake

    1. AHAndrew Huberman41:44

       so now that you understand that getting your cortisol high upon waking is the right thing to do, this is what you want, let's talk about some of the other things you can do besides viewing bright light in order to increase your morning cortisol. But keep in the back of your mind that viewing bright light is the foundation. Okay, so you wake up in the morning, and as quickly as you can, you get bright light into your eyes. What else should you do to boost your cortisol? Well, there are a number of things that you can do and that you should do every single day. Most of them are pretty easy, and many of them can be combined. One of those is hydration. Now, of all the protocols in the realm of mental health, physical health, and performance, I think the most underrated one, believe it or not, is hydration. When you look at the literature on hydration and the effects of even mild dehydration, what you find is that cognitive function, physical function, basically cellular function and organ function generally, all suffer when you're even mildly dehydrated. So it's very important that you hydrate first thing in the morning. For me, that's 16 to 32 ounces of water with some electrolytes in it. For you, it might just be water, whatever. The interesting thing is that one of the major effects of proper hydration is to increase levels of alertness, and the way it does it is by acting on the adrenals, both...Epinephrine, adrenaline, and cortisol release. And we're not talking about big spikes in cortisol related to drinking water. We're talking about modest increases in the levels of pulsatile, as it's called, release of cortisol due to hydration. So hydrating first thing in the morning, also a terrific idea. You can do this while you get your bright light outside or while you get your bright light from a 10,000 lux artificial source. Hydrate first thing in the morning. It's going to increase your levels of energy then and throughout the morning and into the afternoon. Again, highly underrated protocol, in part because it takes a lot, a lot of dehydration before we realize that we're dehydrated. When you wake up in the morning and you use the restroom, you're probably mildly dehydrated. Get yourself hydrated first thing in the morning. Your cortisol levels will thank you. Your levels of energy will thank you. Now, if you're like me, you also hydrate with caffeine, okay? (laughs) Now, the discussion around caffeine and cortisol can be a little bit confused by the sort of discrepancies in the literature as to, yes, caffeine increases cortisol, or some studies that show, no, caffeine doesn't increase cortisol, but it might extend the life of cortisol. Here's the big picture on caffeine and cortisol, at least the meaningful one. If you're a chronic caffeine user, meaning you drink caffeine every day or you've consumed caffeine every day for the previous five days, which is the typical framework in one of these studies, and then you drink caffeine, 100 milligrams, 200 milligrams, 300 milligrams, even an energy drink that includes caffeine and some other things, the increase in cortisol that you're going to experience is probably not that significant unless it's a massively elevated dose of caffeine for you. However, if you're somebody who's not caffeine-adapted, you're not drinking caffeine every day, you haven't had it for the last five days, then yes, you will experience a significant increase in cortisol levels. So you have to ask yourself, are you a chronic caffeine user? Are you an occasional caffeine user? Or do you not use caffeine? If you're somebody who avoids caffeine because it makes you anxious or you just don't like it, then by all means, don't drink caffeine just to spike your cortisol. It will be very effective in spiking your cortisol, but I can't really encourage you to drink caffeine if you don't want to. If, however, you're somebody who regularly drinks caffeine, you now know that it's not going to boost your cortisol levels that much, maybe a little bit, depending on how much you drink. If it's a typical amount for you, meaning you're caffeine-adapted to that amount of caffeine, probably not much cortisol increase will come from drinking that amount. However, it will prolong the duration of cortisol's effectiveness in your bloodstream. And this has to do with a number of different pathways, but the point being, if you have your caffeine, say, 30 minutes after waking or five minutes after waking or 90 minutes after waking, well, it's probably not going to boost your cortisol levels that much if you're already viewing bright sunlight, you're hydrating. We'll talk about exercise and some other things in a moment, but if you're drinking that caffeine shortly after waking up or shortly, close to when you get that big cortisol spike, it's going to make the downslope of that cortisol spike a bit more gradual, or if you're drinking caffeine throughout the morning, a lot more gradual. So let me present two scenarios in which you can use caffeine to improve your levels of mood, focus, and alertness by way of the cortisol pathway, and here, I'm only speaking to people who habitually use caffeine, so you're drinking caffeine every morning. The first group is one that I commonly encounter. These are people that say, "Listen, I don't care what I hear out there. I want my coffee," or, "I want my yerba mate," which is my preferred source of caffeine, "first thing in the morning," right? Ideally, even before water. Well, there, I'd say please drink water first, but even if you're not going to, sure, go ahead and drink your caffeine. Drink that caffeine. It's not gonna boost your cortisol that much, but make sure you're doing a bunch of other things, bright light viewing, we'll talk about exercise in a moment, et cetera. Do a bunch of other things to make sure that morning cortisol spike is really, really high, because that's what you want. Now, there's a second group of people that say, "Hey, I want my caffeine first thing in the morning," or, "I'm drinking my caffeine first thing in the morning, but then I'm crashing really hard in the late morning, crashing really hard in the afternoon, and it's not because I'm not sleeping well at night. It's like something's happening." This is where the recommendation that I've been making for some years now of delaying your caffeine by anywhere from 60 to 90 minutes comes about. You now know that caffeine, for a habitual user, is not going to increase your cortisol levels that much. However, you also now know that drinking caffeine will extend the life of cortisol somewhat. So the logic here is if you drink your caffeine not immediately after waking, but let's say an hour after waking or 90 minutes after waking, it's going to flatten out a bit the downslope of that cortisol as you transition from late morning into the early afternoon. A lot of reason why people crash in the afternoon, they get that extreme fatigue, typically after lunch, yes, it can be due to eating too much at lunch. Yes, it can be due to eating too many starchy carbohydrates or sugars at lunch. It can be due to lack of sleep, but assuming that you're doing all the things right and you're still experiencing that crash in the afternoon, there's a good chance that it's because your morning cortisol peak, high enough or no, is coming down too fast, and in order to make it more gradual, you simply shift your caffeine intake a little bit later so that that diminishing caffeine level that it starts to occur around 10:00 AM, 11:00 AM, of course, all of this relates to exactly when you wake up, but that dropping level in caffeine isn't a steep cliff. It's a little bit more gradual. And I can't tell you how many thousands of people have contacted me and said, "Oh my goodness, I can't believe it. Simply by pushing out my caffeine intake by 60 minutes or even 30 minutes, or in some cases 90 minutes after waking, I've been able to not experience that crash in energy in the afternoon." And they generally thank me for this. Indeed, most all of them are writing to me to thank me for this. For those of you that...Absolutely love your caffeine first thing in the morning, you want your caffeine first thing in the morning and you just refuse to delay it, fine. I never, ever said that you couldn't do that. In fact, you can do whatever you want. I'm simply giving you an opportunity to extend the life of that morning cortisol pulse. Caffeine's a great way to do that. And for those of you that don't consume caffeine regularly, but like to use it as an occasional tool, like if you need to stay up late, for instance, or, you know, only under conditions in which you really, really need to wake up quickly, well, in that case, it's actually going to be a pretty terrific tool because you will indeed achieve a big increase in cortisol, energy, and alertness, which for the rest of us habitual caffeine users where you're seeking every day, we're drinking our caffeine, and it's harder and harder to get. That's just the nature of caffeine tolerance. Okay,

12. 49:30 – 57:52

    Exercise, Entrainment Cues & Cortisol Rhythm, Tool: Boost Energy & Exercise Schedule

    1. AHAndrew Huberman49:30

       let's talk about exercise and its effects on cortisol. In many ways, exercise's effects on cortisol are similar to those of caffeine, and I say that because it really depends on how regularly you perform a particular type of exercise. Now, studies of the effects of exercise on cortisol are complicated by the fact that sometimes they looked at people who are regular exercisers, let's say they were runners, they look at the effects of running on cortisol, or they were resistance trainers, okay? So they do weightlifting and then they look at the effects of weightlifting on cortisol. They look before, during, and after, this kind of thing. They look as a function of frequency of training. All of that's been done. However, some labs have also explored the effects of, say, runners who take up resistance training or people who are non-exercisers who suddenly start resistance training or running. When I looked at all of that literature, you come away with a picture where, just like with caffeine, if you are accustomed to exercising in a particular way and at a particular time of day, the elevation in cortisol that you experience from that workout is going to be less than if it's a completely novel scenario, both in terms of time and the type of workout. In other words, if you're like me and you like to exercise within the first three hours of the day and you exercise in the first three hours of the day doing either resistance training or cardiovascular exercise, because I'll do both on separate days, but I'll do both, neither of those is particularly novel to me, and I do those at the intensity that is familiar to me, which for me is moderate to high intensity, well, the increase in cortisol that one experiences is not that great. You get big increases in other things like the catecholamines, dopamine, epinephrine, and norepinephrine, and yes, you do get some increase in cortisol, in particular in the late stages, meaning late in the first hour of exercise. Typically, my resistance training sessions don't span longer than 90 minutes. That includes the warmup and the cooldown. So after about 70 minutes of resistance training with real effort, close to failure or to failure, you know, this kind of thing, cortisol levels are way up and they'll stay up for a short while, meaning an hour or so after exercise, and then they'll come back down, especially if you're doing things to deliberately bring them down, including eating a meal laden with carbohydrates will, which will help bring those, uh, cortisol levels down. But if, for instance, somebody who's never resistance trained or who's primarily an endurance athlete starts resistance training in that way, the literature points to the fact that they will experience much higher cortisol levels and those cortisol levels will be sustained over many more hours. The same thing could be said for endurance exercise or for high-intensity interval training. I don't want to complicate things too much by spelling out each of the different scenarios. I will provide a link to it, what I consider a really nice paper. It's just one of the several pointing to this, but the title of the paper is Endocrine Responses of the Stress System to Different Types of Exercise, and they looked at single bout endurance, regular endurance, single bout high-intensity exercise, regular high-intensity exercise, single bout resistance, regular resistance. So they went through not all, but many of the permutations that are possible and spell out what are the effects on cortisol, what are the effects on the catecholamines, norepinephrine and epinephrine in this case, what are the effects on inflammatory cytokines? We sometimes forget this, but inflammatory cytokines are a healthy byproduct of exercise because those trigger the adaptations in your immune system and other tissues to adapt, to get stronger, including your immune system. And they also looked at growth hormone. It was kind of interesting because where you find big increases in cortisol, you also see big increases in growth hormone in response to exercise, meaning when the exercise is novel, either because it's a new form of exercise or because the intensity is novel. So we can take a step back and say with certainty, exercise increases cortisol. However, if the form of exercise and the timing is very familiar to you, the amount of cortisol, and in particular the duration of cortisol increase, is not going to be that significant as compared to if it's a completely novel form or timing of exercise. Now, is the increase in cortisol that's achieved with your, let's call them your regular workouts, right? Typically, if you run or you lift weights or you do some sort of interval training, if you're doing any number or just one of those things, is the amount of cortisol increase that you experience going to be significant in terms of helping you anchor that cortisol cycle so that cortisol is higher in the morning and lower in the afternoon and evening? The answer is yes. Exercise of a type that's familiar to you, of an intensity that's familiar to you, may not significantly increase your cortisol levels as compared to a form of exercise that's completely novel. However, exercise provides a very strong what's called entrainment cue. Entrainment cues are cues of things that we do, these could be meals, it could be light exposure, could be exercise, it could be all sorts of things, even social engagement, that feed back onto the SCN, the suprachiasmatic nucleus, and reinforce the timing of the cortisol release that the SCN causes. So there are these beautiful interactions between exercise, the SCN, and cortisol release, that when we exercise at roughly the same period of time each day, doesn't have to be right on the minute, but within the same two or three-hour window each day, and since like most people you're probably not exercising every single day, perhaps three days a week, four days a week, ideally five or six days a week, uh...When you do that, pretty soon you get a cortisol increase simply in response to the timing rolling around in a very Pavlovian way, even if you don't exercise. Now, you have to keep exercising to maintain that, but the, the key here is that when you exercise in the same two to three hour window each day, or at least three days a week, ideally four, five, six days per week, I do think it's important to have at least one complete rest day. When you do that, that big peak in cortisol that's endogenously generated by your SCN, that's just internally generated without doing anything else, it gets anchored to that stage of the day in a very solid way, as compared to people who don't exercise early in the day. So the point here is that you exercise, sure, to increase your cortisol, but probably for a bunch of other reasons more than you do to increase your cortisol. But getting your cortisol rhythm correct is absolutely essential. In fact, it's going to give you the anticipatory energy for exercise. In fact, you can try this. It's remarkable. If you exercise at the same time of day for, say, four to five, maybe six days per week, you just do that for a week, and it doesn't have to be, again, exactly at the same time you start, exactly the ta- same time you stop, plus or minus 30 minutes, what you'll find is that in the hour leading into that exercise, you will start to experience an increase in energy. And it's not just psychological. There's an anticipatory rise in cortisol that's governed by the SCN and this process that we call entrainment, which is anticipation, it's kind of like a Pavlovian response, but it's on a longer timescale. Well, regardless of timescale, it's a very real thing. So if you're somebody who doesn't seem to have much energy, much get up and go in the morning, and you're getting your bright light, you're getting your hydration, maybe you're even drinking caffeine, you're doing all of that and you're still feeling kind of sluggish, exercising for three or four days, not necessarily in a row, feel free to introduce a rest day as needed, but doing that across the course of a week for four to six days will lead you into a second week, a third week, et cetera, provided you keep it up, where you're going to have more energy heading into the exercise, therefore more energy to exercise. It's just gonna be a positive feedback loop on your cortisol levels. This is a very robust effect, and in fact, it's so robust that you can observe it in mice, you can observe it in dogs. Your dog knows when it's time for a walk even if you don't say, "Walk." It has internal endogenous cues that, you know, between the hours of, whatever, 7:00 and 9:00 AM it's time for a walk, and it will start to experience a surge in energy. You are the exact same way. These are hardwired, very long established systems in our brain and body, and you can absolutely give yourself more energy to do the things that require energy by exercising at roughly the same time. Again, within the same three-hour window is probably the broadest, but, you know, even better would be in the same two-hour window each day. And if you miss a day, no big deal. You'll just have more energy during that time to devote to other things.

13. 57:52 – 1:01:19

    Does Deliberate Cold Exposure Increase Cortisol?, Energy & Mood

    1. AHAndrew Huberman57:52

       Okay, what about deliberate cold exposure? Cold showers, cold plunges, this kind of thing. You all know that deliberate cold exposure wakes you up, okay? Despite it being somewhat controversial (laughs) in other domains like metabolism, deliberate cold exposure definitely wakes you up, and it wakes you up very fast, and it does that because it causes the release of epinephrine and norepinephrine, and then you get this long arc of dopamine release. This is one of the major reasons, if not the major reason why people who start deliberate cold exposure continue to do it, right? If for no other reason, it wakes people up, makes them feel good for many hours afterwards. Now, I know many people are averse to the cold, they really don't like it, and frankly, if you don't like it, you don't have to do it. But it absolutely causes an increase in the catecholamines, dopamine, epinephrine, and norepinephrine, and the long-lasting effects on dopamine are quite striking, meaning there are very few other things that can cause that long, slow release of dopamine to the levels that it does, which changes mood, alertness, et cetera for many hours after. Now, the big question for sake of this discussion is, does deliberate cold exposure cause the release of cortisol? And just like with exercise, just like with caffeine, the real question that we have to ask ourselves is, how novel, how unfamiliar is that deliberate cold exposure? Because while the perfect experiment has never really been done, if you amass the literature on this, what you find is that if you put people into very cold water, or even just cold for them, uncomfortably cold for them, water, yes, they'll increase more cortisol, yes, they'll release cortisol into their bloodstream. However, if they do this habitually, then the increases in cortisol are not meaningful, they're not statistically significant. So that actually leads to two important takeaways. The first one is, if you want to use deliberate cold exposure as a way to increase cortisol, great, do that, but probably don't do it more than say, one or two times per week. Otherwise, it will lose its effectiveness for that purpose. It will still be very effective for all the other reasons that deliberate cold exposure has been purported to be effective, including increased release of catecholamines. So the takeaway here is very straightforward. If you want to boost your cortisol levels using deliberate cold exposure, cold shower, ice plunge, whatever it is, you can do that. But it needs to be occasional deliberate cold exposure, probably not more than twice per week. Otherwise, you're not going to get a significant increase in cortisol as a consequence of that deliberate cold exposure. However, if you're somebody who likes doing deliberate cold exposure, keep in mind that it's not going to chronically elevate your cortisol. This is advantageous for a number of reasons. First of all, it will, yes, continue to elevate your levels of dopamine, norepinephrine, and epinephrine for increased mood and energy. That effect persists. As far as we know, that effect never saturates. But if you're somebody who's concerned about elevating your cortisol too much, you're concerned about chronic elevation of cortisol, and I hear a lot about this in the circles around, you know, important differences between men's fitness and health and women's fitness and health, and maybe that deliberate cold exposure is good for men and not for women, there's really no evidence to support that. In fact, the evidence points in exactly the opposite direction, which is that when people, men or women, do deliberate cold exposure regularly more than twice per week, then the impact on cortisol is not significant, and yet they still can benefit by getting those increases in dopamine, epinephrine, and norepinephrine.I'd like

14. 1:01:19 – 1:02:51

    Sponsor: LMNT

    1. AHAndrew Huberman1:01:19

       to take a quick break and acknowledge one of our sponsors, LMNT. LMNT is an electrolyte drink that has everything you need and nothing you don't. That means the electrolytes, sodium, magnesium, and potassium in the correct amounts, but no sugar. Proper hydration is critical for optimal brain and body function. Even a slight degree of dehydration can diminish cognitive and physical performance. It's also important that you get adequate electrolytes. The electrolytes, sodium, magnesium, and potassium are vital for functioning of all the cells in your body, especially your neurons or your nerve cells. Drinking LMNT dissolved in water makes it very easy to ensure that you're getting adequate hydration and adequate electrolytes. To make sure that I'm getting proper amounts of hydration and electrolytes, I dissolve one packet of LMNT in about 16 to 32 ounces of water when I first wake up in the morning, and I drink that basically first thing in the morning. I'll also drink LMNT dissolved in water during any kind of physical exercise that I'm doing, especially on hot days when I'm sweating a lot and losing water and electrolytes. LMNT has a bunch of great-tasting flavors. I love the raspberry, I love the citrus flavor. Right now LMNT has a limited edition lemonade flavor that is absolutely delicious. I hate to say that I love one more than all the others, but this lemonade flavor is right up there with my favorite other one, which is raspberry or watermelon. Again, I can't pick just one flavor. I love them all. If you'd like to try LMNT, you can go to drinklmnt.com/huberman, spelled drink L-M-N-T dot com slash Huberman to claim a free LMNT sample pack with the purchase of any LMNT drink mix. Again, that's drinklmnt.com/huberman to claim a free sample pack. Okay.

15. 1:02:51 – 1:11:34

    Increase Morning Cortisol & Nutrition, Grapefruit, Black Licorice

    1. AHAndrew Huberman1:02:51

       Let's talk about some of the other things that you can do to increase your morning cortisol levels. If you're starting to get the picture that cortisol is something that you want high early in the day and that you want tapering off later into the day, great. Then you're getting the picture correctly. In fact, one way to think about it is that cortisol is kind of like a wave that starts on its own but for which you can increase the height of that wave and catch that wave early in the day and into the afternoon. If you imagine it that way, then you're probably saying, "What other things can I do besides viewing light, besides hydration, besides caffeine, besides exercise?" And probably part of the reason you's asking is that not all of us are able to do all of those things every single day. I do acknowledge that. So the larger the toolkit of things that you can use to increase your morning cortisol peak, the more flexibility you have when trying to come up with those when traveling, when especially busy, and so on and so forth. So if we take a step back and ask ourselves what sorts of chemical compounds out there can help us increase our cortisol levels, we come up with some pretty interesting answers. And no, we're not going to talk about supplements. It is true that certain supplements like yohimbine, like L-tyrosine can have a modest effect in increasing cortisol, but we're not going to emphasize those. We're actually going to emphasize two naturally occurring foods that have a significant impact on cortisol levels, both the amount of cortisol that you're capable of releasing early in the day and the duration for which that cortisol lasts. The first one is, of all things, grapefruit. Yes, grapefruit. Here I'm talking about the whole fruit. Could be pink grapefruit, could be not pink grapefruit, yellow grapefruit, could be grapefruit juice. And before I get into the mechanism and the protocol, I should emphasize that the effects of grapefruit on cortisol are not trivial. They're significant. So if you eat a grapefruit or you drink, uh, I don't know, six to eight ounces of grapefruit juice, it's going to have a meaningful impact on how long the cortisol that's already in your bloodstream lasts. The way it does that is grapefruit contains compounds that inhibit the enzymes that break down cortisol. In particular, compounds in grapefruit inhibit the action of an enzyme called CYP3A4, and maybe A5 as well, and that enzyme is responsible in large part for breaking down cortisol. It's not the only way that cortisol is broken down, but it's one of the major ways. And grapefruit has a significant impact in inhibiting the enzyme that breaks down cortisol. So believe it or not, many studies have been done in humans, men and women, and the net takeaway is the same in every case. If you were to eat a grapefruit, you're going to extend the life of cortisol in your bloodstream by anywhere from 25 to 50%. All right? That's significant, and it has actually been shown to be clinically significant. And the reason I say clinically significant in this case is that indeed there are some people that need to deliberately elevate their cortisol using medication. Those people typically are instructed not to eat grapefruit or drink grapefruit juice because then they're not going to get as clear a picture on how a given dose of their medication is impacting their cortisol. Likewise, people who have chronically elevated cortisol are told not to eat grapefruit or drink grapefruit juice because it can further elevate their cortisol. However, most people who don't have things like Cushing's disease or Addison's don't have to worry about this, and most people, probably you, are interested in having a lot more energy, get up and go early in the day, and you now know that elevating your morning cortisol is one way to do that. And many of you, presumably, don't always have time to exercise or you don't always have time to get morning light. I know it sounds outrageous, but every once in a while, you can't get sunlight or bright light into your eyes. Well, you might be thinking about ways that you could increase your cortisol under those conditions. Well, eating a grapefruit would do that or drinking some grapefruit juice. And of course, you can eat a grapefruit or drink some grapefruit juice in combination with all the other things that we've discussed. In fact, there are compounds in grapefruit juice that will also extend the effectiveness of caffeine. So this effect of grapefruit on the various enzymes that break down things like caffeine and cortisol is a meaningful impact. It's not a trivial one. And so while it might seem kind of silly to say, "Oh, yeah, eat grapefruit to increase your morning energy," it's actually a real thing that's separable from the effects of grapefruit on, say, blood sugar, that comes from the fructose in grapefruit, that comes from the vitamins and minerals and other things in grapefruit. There's a real and meaningful impact of grapefruit on the cortisol breakdown pathway. So if you're interested in boosting your morning cortisol, simply eat a grapefruit in the morning. I've started doing that late morning. I typically eat my first meal of the day somewhere around 10:30, 11:00 AM. It sort of varies from day to day. I don't typically eat first thing upon waking.I do drink caffeine first thing upon waking if I'm going to exercise. Most other days, I delay my caffeine a bit. In any case, in the last few weeks as I've been researching this episode, I've started consuming one pink grapefruit, which I personally find delicious, late morning before my first meal, and indeed, I notice a tangible increase in energy both late morning and into the early afternoon. Yes, perhaps some of that is placebo effect because I anticipated this effect of grapefruit, but the data and the literature and the mechanistic pathway is very clear. Grapefruit extends the life of cortisol. The other food that can increase cortisol is licorice, in particular, black licorice. We're not talking about red licorice. We're talking about black licorice. You might be thinking, "What is this? Are we, like, getting into the realm of, like, really alternative medicine?" No. All you have to do is look at the list of things that people who are trying to reduce their cortisol or who are taking medications to increase or decrease cortisol for a disease state are told not to eat, and you get an insight into just how powerful licorice is, or I should say things within licorice, are for increasing cortisol levels. What I'm talking about here is a compound called glycyrrhizin. Glycyrrhizin is in black licorice, and glycyrrhizin has been shown to have very big effects on increasing cortisol, so much so that if you are going to experiment with licorice or glycyrrhizin that comes from licorice root, you need to actually be pretty careful to not boost your cortisol levels too much. Start with the lowest possible dose of licorice root if you're going to use it in capsule form. If you're going to eat black licorice, a lot of people like black licorice. A lot of people are averse to black licorice. It's kind of a, um, individual thing. If you're going to do that, you're going to need to be cautious about not spiking your cortisol too much, especially if you're eating it later in the day. We're not to late-day cortisol control just yet. But licorice significantly boosts your cortisol levels, and it does so by inhibiting the enzyme 11-beta-hydroxysteroid dehydrogenase, or 11-beta-HSD for short. This is the enzyme that's involved in the conversion of cortisol to cortisone. So cortisol, when released into the blood, eventually is broken down into a bunch of other things, and in order to keep the cortisol active, and here we didn't get into a discussion about cortisol either being bound or free, okay? The free form is the one that's active and can impact tissues, just like free testosterone can impact tissues as opposed to bound testosterone. Because it's also a steroid hormone, cortisol goes through some of the same regulation. The important point here is that licorice can be used to potently increase cortisol, not just the duration of cortisol's impact, but also apparently the release of cortisol. Now, the data on that are a little bit mixed. Some people would even argue that licorice can increase the synthesis of cortisol, but there, there's even less data. The data are very clear, however, that glycyrrhizin, which is prominently found in black licorice, you are going to increase the amount of cortisol circulating in your bloodstream. So if you're having a really difficult time boosting your cortisol in the morning despite doing all the other things that I'm describing, or let's just say there's a day in which you can't exercise, you don't have access to bright light, you can't do all the things that you would need to in order to boost cortisol, but you want to, maybe that's the day that you try a small amount of licorice root or a small amount of black licorice. One very important point, licorice has a potent enough effect on cortisol and cortisol has a potent enough effect on blood pressure that if you suffer from hypertension or high blood pressure or if you are pregnant or breastfeeding, you absolutely do not want to eat black licorice. I don't know whether or not this is commonly told to women who are pregnant or breastfeeding, but when I looked in the literature, this was a repeated theme. Women who are pregnant or breastfeeding, people with elevated blood pressures should not be consuming black licorice. The glycyrrhizin is potentially hazardous for them or the fetus. So I say that in part to inform you about licorice and its effects on cortisol but also that you be mindful that licorice has a potent effect on the cortisol pathways.

16. 1:11:34 – 1:14:30

    Afternoon & Evening Cortisol Rhythms, Sunlight, Screens

    1. AHAndrew Huberman1:11:34

       Okay, so we've talked about how to control your cortisol in the morning for more energy, focus, alertness, et cetera, all day long. However, your endogenous rhythm of cortisol dictates, right, you don't have control over this, it dictates that your cortisol is going to start to fall somewhere around noon, maybe 11:00 AM, maybe noon, maybe 1:00 PM. Remember, it all depends on when you woke up because waking up is actually what triggers that big inflection in cortisol early in the day. But as your cortisol starts to fall into the early afternoon, late afternoon, and so on, you may notice something, which is you can experience stress. Sure, if you have a stress event, you'll get a spike in cortisol, and it will come back down. But if you've ever been outside during the middle of the day, got some sunlight in your eyes, maybe sitting with your eyes closed, maybe even relaxing in the sun, you'd probably say, "Getting bright light in my eyes, getting sunlight in the afternoon keeps me calm. If anything, it makes me mellower. It doesn't tend to wake me up." But remember, it was only in the first hour or so after waking up in the morning that bright light causes this big inflection in your cortisol and contributes to more energy. In the afternoon, that system is gated. It's shut down. This is what's referred to as the circadian dead zone in circadian biology. You can't actually shift your biological clock with light at that time, which doesn't mean that getting sunlight on your skin or in your eyes isn't a good thing. It indeed is a good thing. Of course, you want to guard yourself against too much UV exposure by wearing clothing or perhaps a mineral-based sunscreen, et cetera, but getting sunlight in the middle of the day can be a terrific thing for your mood. There are great studies showing that it can enhance hormone production, including testosterone and estrogen, feelings of well-being, but indeed, getting sunlight and other forms of bright light in your eyes and on your skin in the afternoon tends to make you feel kind of relaxed, and that's because that positive feedback loop that the SCN can trigger whereby light increases your cortisol is completely shut down from the hours of about noontime or so until about 5:00 or 6:00 in the evening.Now I say until about 5:00 or 6:00 in the evening because in the evening, cortisol is going even lower, lower, lower. But then something happens. The gate, the opportunity for light to start triggering increases in cortisol opens. And as you'll soon learn, not only does it open, but it's extra sensitive. Put differently, in the evening past sundown, so this will be different different times of year, different locations on Earth, but about two hours after sundown or so, any bright light from an artificial source, especially short wavelength light of the type that comes from LEDs and computer screens and phones, that sort of thing, can cause big increases in cortisol. And that, of course, provides a perfect segue for us to talk about the things that you should do in the evening and at night to make sure that your cortisol is low and dropping further still.

17. 1:14:30 – 1:20:54

    Lower Evening Cortisol, Tools: Dim Lights, Light Color

    1. AHAndrew Huberman1:14:30

       Okay. So let's talk about the things to do in the evening and at night in order to, quote-unquote, "optimize your cortisol levels." And when I say optimize, of course, there's no optimal exact level. There's no optimal level for one exact time. Everyone's on slightly different schedules. I tend to go to sleep somewhere between 10:00 PM and midnight most nights. Sometimes it's 9:30. Sometimes I'll stay up past midnight. It happens every once in a while. You may go to bed at 8:00. You may go to bed at 1:00 AM. The point here is that we're focused now on the portion of your endogenous, naturally generated cortisol rhythm that occurs in the hours before bedtime when your goal is to get to sleep and get terrific sleep. And what that requires is that your cortisol is low and continuing to go lower. So there are various things that you should do in the afternoon and evening and nighttime to make sure that pattern occurs. The first has to do with lighting. As I just described in the evening, about two hours after sundown is really when this phase of your cortisol cycle begins, where not much light is required in order to create big increases in cortisol, which is the exact opposite of what you want in the evening and at night. You want your cortisol going down, not up. So, how do you control your lighting in order to ensure that pattern occurs? There are several ways. First of all, you just dim the indoor lights, right? Dim them as much as possible, especially overhead lights. The neurons in your eye that send information about overall luminance, how bright it is in your environment, they're all over your eye, but they reside primarily in the lower two-thirds of your eyes, because their role is to view the upper visual field, and that's how that circuit is arranged. So if you have to have lights on in your indoor environment at night, which most people do, you should dim as many lights as you can, turn off as many overhead lights as you can. Table lamps are better than overhead lights, and floor lights are better than table lamps. Most people aren't gonna install floor lights. But if you find that you're having trouble mellowing out and getting to sleep and there isn't some other reason for that, like you drank a bunch of caffeine at 8:00 PM or 6:00 PM, then dimming the lights is going to be a terrific idea. Now, the wavelength, the color of those lights can also have a big impact. As I mentioned before, you want to avoid short wavelength light exposure. So this would be your white LED lights, blue lights, green lights if you can. All right? And there are various ways you can do this. You could purchase a red light bulb. I'm not talking ab- talking about red light therapy, but there are various sources of red lights that you can install. They're very inexpensive. Again, it's not red light therapy. It's just restricted such that I'm only getting long wavelength light in my eyes. Why? Well, there are a number of papers showing that if we restrict our visual exposure to medium and long wavelength light in the evenings and at night, it does not have nearly as much impact on increasing cortisol. Now, if it's very, very bright, we're talking, like, bursting bright red lights, it can increase cortisol even in the evening. But if it's relatively bright to dim red light or amber-colored light of the sort that you would get with an incandescent bulb as opposed to an LED bulb, that's going to keep cortisol low. And the effect of these lighting changes is not trivial. These are meaningful protocols that will actually help keep your cortisol low, help keep you calm and mellow. And of course, you should dim the screen on your phone and your computer. There's actually a way, if you have an Apple phone, that you can very easily program in a triple-click shortcut so that your screen turns red. We can provide an instruction of how to do that in the show note captions. It takes about two minutes to do. I have this on all my phone devices, so you can triple-click on the side and then it brings your phone screen, uh, from its standard, uh, luminance to a, basically a red screen. So it cuts out all the short wavelength light. And of course, if you're interested in using glasses that restrict short wavelength light, as some of you probably know, I worked in collaboration with ROKA Glasses to develop what we call the Winddown Glasses. They're not just blue blockers. They don't just cut out the blue wavelengths of the visual spectrum. They cut out all the short wavelength light that can stimulate the cells that can increase cortisol and so on and so forth. So the glasses are convenient because oftentimes you don't have control over your indoor lighting environment, right? If you're out

Episode duration: 2:16:15