Using Science to Optimize Sleep, Learning & Metabolism | Huberman Lab Essentials

welcome to hubman lab Essentials where we revisit past episodes for the most potent and actionable science-based tools for mental health physical health and performance I'm Andrew huberman and I'm a professor of neurobiology and Opthalmology at Stanford school of medicine today is episode three of the podcast and it is office hours office hours as many of you know it's where students come to the office of the professor sit down and ask questions requesting clarification about things that were confusing or to Simply go down the route of exploring a topic with more depth in detail somebody asked what is the role of Moonlight and fire I'm presuming they mean fireplace or candle or things of that sort in setting circadian rhythms is it okay to view Moonlight at night or will that wake me up will a fire in my fireplace or using candle light be too much light great question turns out that Moonlight candle light and even a fireplace if you have one of these roaring fires going in the fireplace do not reset your circadian clock at night and trick your brain into thinking that it's morning even though if you've ever sat close to a fireplace or even a candle that light seems very bright and there are two reasons for that that are very important the first one is that these neurons in your eye that I discussed in the previous episode These melanops and gangan cells cells also called intrinsically photosensitive gangan cells those cells adjust their sensitivity across the day and those cells respond best to the blue yellow contrast present in the rising and Setting Sun so-called low solar angle Sun also discussed in the previous episode but those cells adjust their sensitivity such that they will not activate the the triggers in the brain that convey daytime signals when they View Moonlight even a full moon a really bright moon or fire because we talked about just how crucial it is to avoid Bright Lights between the hours of about 10: p.m. and 4:00 a.m. except when you need to view things for sake of safety or um or work or so and so forth I also received a lot of questions about red light in principle red light will not stimulate the melanops and retinal neurons that wake up the brain and circadian clock and Signal daytime however most of the red lights in particular the red lights that come in these sheets of these products that people are supposed to view the um in order to access a number of uh you know health effects those are way too bright and would definitely wake up your body and brain so if you're thinking about red light for sake of avoiding the negative effects of light later in the day and at night then you want that red light to be very very dim certainly much dimmer than is on most of those commercial products now do you need red lights no although red lights are rather convenient because you can see pretty well with them on but if they're dim they won't wake up the circadian clock they won't have this dopamine disrupting thing that we talked about in the previous podcast okay a huge number of people asked me about light through window setting your circadian clock with sunlight coming through a window is going to take 50 to 100 times longer you can download the free app light meter you can have a bright day outside or some sunlight hold up that app take a picture it'll tell you how many luxs are in that environment now close the window and if you want close the screen or don't open the screen you can do all sorts of experiments you'll see that it will at least half the amount of Lux and it doesn't scale linearly meaning let's say I get uh 10,000 Lux outside 5,000 looking out through an open window and then I close the window and it's 2500 Lux it does not mean that you just need to view that sunlight for um twice as long if it's half as many luck okay it's not like 25 100 Lux means you need to look for 10 minutes and um 5,000 Lux means you look for 5 minutes it doesn't scale that way just because the biology doesn't work that way best thing to do is to get outside if you can if you can't next best thing to do is to keep that window open it is perfectly fine to wear prescription lenses and contacts why is it okay to wear prescription lenses and contacts when those are glass also but looking through a window diminishes the effect well we should think about this the lenses that you wear in front of your eyes by prescription or on your eyes are designed to focus the light onto your neural retina so let's think about why I'm making some of these recommendations because I think it can really Empower you with the ability to change your behavior in terms of light viewing and other things depending on time of year depending on other lifestyle factors the important point to understand is that early in the day your central circadian clocks and all these mechanisms are looking for a lot of light okay I want to talk about seasonal changes in all these things as they relate to mood and Metabolism so as all of you know the Earth spins once every 24 hours on its axis so part of that day we're bathed in sunlight depending on where we are the other half of the day or part of the day we're in darkness the Earth also travels around the Sun 365 days is the time that it takes one year to travel around around that zone the Earth is tilted it's not perfectly upright so the Earth is tilted on its axis so depending on where we are in that 365 day journey and depending on where we are in terms of hemisphere Northern Hemisphere southern hemisphere some days of the year are longer than others some are very short some are very long if you're at the at the equator you experience less variation in day length and therefore night length and if you're closer to the poles you're going to experience some very long days and you're also going to experience some very short days depending on which poll you're at and what time of year it is the simple way to put this is depending on time of year the days are either getting shorter or getting longer now every cell in your body adjusts its biology according to day length except your brain body and cells don't actually know anything about day length it only knows night length and here's how it works light in inhibits melatonin powerfully if days are long and getting longer that means melatonin is reduced if days are getting shorter that melatonin signal is getting longer so every cell in your body actually knows external day length and therefore time of year by way of the duration of the Melatonin signal by understanding that light and extended daylength inhibit melatonin and melatonin tends to be associated with a more depressed or reduced functioning of these kind of activity driving and um mood elevating signals and understanding that you have some control over melatonin by way of light including sunlight but also artificial light that should Empower you I believe to make the adjustment so that if you're feeling low you might ask how much light am I getting when am I getting that light because sleep is also important for restoring mood right so you need sleep you can't just you know just just Crush melatonin across the board and expect to feel good because then you're not going to fall asleep and stay asleep melatonin not incidentally comes from is synthesized from serotonin serotonin is a neurotransmitter that is associated with feelings of well-being provided to proper levels but well-being of a particular kind well-being associated with quiessence and calm and the feeling that we have enough resources in our immediate kind of conditions it's the kind of thing that comes from a good meal or sitting down with friends or holding a loved one or um conversing with somebody that you really bond with serotonin does not stimulate action it tends to stimulate Stillness very different than the neuromodulator dopamine which is a reward feel-good neuromodulator that stimulates action and actually dopamine is the precursor to epinephrine to Adrenaline which actually puts us into action there it's actually made from dopamine right so you can start to think about light as a signal that is very powerful for modulating things like sleep and wakefulness but also serotonin levels melatonin levels and I talked about this previously but I'll mention once more that light in the middle of the night reduces dopamine levels to the point where it can start causing problems with learning a memory and mood that's one powerful reason to avoid bright light in the middle of the night throughout this podcast and in previous episodes I've been mentioning neuromodulators things like serotonin and dopamine which tend to bias certain brain circuits and things in our body to happen and certain brain circuits and things in our body not to happen one of the ones I've mentioned numerous times is epinephrine which is a neuromodulator that tends to put us into action make us want to move in fact when it's released in high amounts in our brain and body it can lead to what we call stress or the feeling of being stressed several people ask me what's the difference between epinephrine and adrenaline adrenaline is secreted from the adrenal glands which sit right above our kidneys epinephrine is the exact same molecule except that it's released within the brain epinephrine and adrenaline are basically the same thing and they T to stimulate agitation and then desire to move got a lot of questions about exercise what forms of exercise are best for sleeping well when should I exercise Etc there are basically two forms of EXC exerise that we can talk about although of course I realize there are many different forms of exercise there's much more Nuance to this but we can talk about cardiovascular exercise where the ideaas is to repeat a movement over and over and over continuously so that'll be like running biking rowing cycling this kind of thing or there's uh resistance exercise where you're moving lifting presumably putting down also um things of progressively heavier and heavier weight that you couldn't do continuously for for 30 minutes now you will see some places aerobic exercise is best done in the morning and weight training is best done in the afternoon I think there's far more individual variation than that um I think there are however a couple windows that the exercise science literature and the Circadian literature points to as Windows related to body temperature in which performance injury um in which performance is optimized injury is reduced and and so on and those tend to be 30 minutes after waking 3 hours after waking and the later afternoon usually 11 hours after waking which is when temperature tends to Peak a note about working out first thing in the morning last time we talked about non-phobic phase shifts if you exercise first thing in the morning your body will start to develop an anticipatory circuit there's actually plasticity in these circadian circuits that will lead you to want to wake up at the particular time that you exercised the previous 3 or 4 days so that can be a powerful tool but you still want to get light exposure because it turns out that light and exercise converge to give an even bigger wakeup signal to the brain and body so you might want to think about that some people find if they exercise late in the day they have trouble sleeping in general intense exercise does that whereas the kind of lower intensity exercise doesn't many of your questions were about neuroplasticity which is the brain and nervous systems ability to change in response to EXP experience there was a question that asked whether or not these really deep biological mechanisms around wakefulness time of waking sleep Etc were subject to neural plasticity and indeed they are some of that plasticity is shortterm and some of it is more longterm there's a really good analogy here which is if you happen to eat on a very tight schedule where every day say at 8:00 a noon and 7 P.M is when you eat your food not suggesting you do this but let's say you were to do that for a couple days after a few days you would start to anticipate those meal times where no matter where you were in the world no matter what was going on in your life about 5 to 10 minutes before those meal times you would start to feel hungry and even a little agitated which is your body's way of trying to get you to forge for food and that's because of some peptide signals that come from the periphery from your body things like hypocretin ereen that signal to the hypothalamus and brain stem to make you active and alert and look for food and feel hungry so there's kind of an anticipatory circuit that's a chemical circuit but eventually over time the neurons the neural circuits that control hypocrite erex and would get tuned to the neural circuits that are involved in eating and maybe even smell and taste to create a kind of eating circuit that's unique to your pattern to your rhythms the same thing is true true for these waking and exercise and other schedules including ultradian schedules if you wake up in the morning and start getting your sunlight you start exercising in the morning or you exercise in the afternoon pretty soon your body will start to anticipate that and start to secrete hormones and other signals that prepare your body for the ensuing activity of waking up or going to sleep so if you get onto a pattern or a rhythm even if that Rhythm isn't down to the minute you'll find that there's plasticity in these circuits and it becomes easier to wake up early if that's your thing or exercise at a particular day if that's your thing that's the beauty of neuroplasticity a number of people asked what can I do to increase plasticity and that really comes in two forms there's plasticity that we can access in sleep to improve rates of learning and depth of learning from the previous day or so and there's this nsdr non-sleep deep breath that can be done without sleeping to improve rates of learning and depth of retention Etc so let's consider th those both and you can incorporate these protocols if you like again these are based on quality peer-reviewed studies first let's talk about learning in sleep this is based on some work that I'll provide the reference for that was published in the journal science excellent Journal Matt Walker also talks about some of these studies um done by others in his book why we sleep the studies just to remind you are structured the following way an individual is brought into a laboratory look does a spal memory task so there tends to be um a screen with a bunch of different objects popping up on the screen in different locations so it might be a bulldog's face it might be a cat then it might be an apple then it might be a pen in different locations and that sounds trivially easy but with time you can imagine it gets pretty tough to come back a day later and remember if something presented in a given location was something you've seen before and whether or not it was presented in that location or a different location if you had enough objects and change the locations enough this can actually be quite difficult in this study PE subjects either just went through the the experiment or a particular odor was um released into the room while they were learning or a tone was played in the room while they were learning and then during the sleep of those subjects the following night and the following night this was done repeatedly for several nights the same odor or tone was played while the subjects were sleeping they did this in different stages of sleep non-rem sleep and rapid eye movement sleep REM sleep they did this with just the tone in sleep uh if they if the subjects had had the odor but not the tone they had they did it with putting the tone if they had had the odor while learning so basically all the controls all the things you'd want to see done to make sure that it wasn't some indirect effect some modulatory effect okay and what they found was that providing the same stimulus the odor if they smelled an odor or a tone if the subjects heard a tone while learning if they just delivered that odor or tone while the subject slept rates of learning and retention of information was significantly greater this is pretty cool what this means that you can cue the subconscious brain the asleep brain brain to learn particular things better and faster so how might you implement this well you could play with this if you want I don't see any real challenge to this provided the odor and uh is a safe one and it doesn't wake you up and the tone is a safe uh safe one and doesn't wake you up um you could do this by having a metronome for instance while um learning something playing in the background or a particular music and then have that very faintly while you sleep so you could apply this if you like and and try this the other form of neuroplasticity is not the neuroplasticity that you're amplifying by listening to tones or um smelling odors and sleep but the neuroplasticity that you can access with non-sleep deep rest so nsdr non-sleep deep rest as well as short 20-minute naps which are very close to non-sleep deep rest because people rarely drop into deep states of sleep during short naps unless they're very sleep deprived nsdr has been shown to increase rates of learning when done for 20 minute bouts for approx to match an approximately 90minut bout of learning so what am I talking about 90minut Cycles are these ultradian cycles that I've talked about previously and we tend to learn very well by taking a 90-minute cycle transitioning into some Focus mode early in the cycle when it's hard to focus and then deep focus and and learning feels almost like agitation and strain and then by the end of that 90-minute cycle so it becomes very hard to maintain focus and learn more information there's a study published in cell reports last year great Journal um excellent paper showing that 20 minute naps or light sleep of a sort of non-sleep De press taken immediately after or close to it doesn't have to be immediately after you finish the last sentence of learning or whatever it is or or bar of music but you know a couple minutes after transitioning to a period of of non-sleep deep rest where you're turning off the analysis of duration path and outcome has been shown to accelerate learning to a significant degree both the amount of information and the retention of that information so that's pretty cool because this is a um cost-free drug-free way of accelerating learning without having to get more sleep but simply by introducing these 20-minute bouts I would encourage people if they want to try this to consider the 20 minutes per every 90 minutes of ultradian learning cycle which brings us to the next thing about learning and plasticity which is neut Tropics AKA smart drugs ah this is a big topic that sigh was a sigh of concern about how to address neut Tropics in a uh thorough enough but thoughtful enough way there are elements to learning that we've discussed here before that are very concrete things like the ability to focus and put the blinders on to everything else that's happening in around you and in your head mainly right distractions about things you should be doing could be doing or might be doing and focus on what you need to do and then that's required for triggering the acetylcholine neuromodulator that will then allow you to highlight the particular synapses that will then later change in sleep so no new Tropic allows you to bypass the need for sleep and deep rest that's important to understand right now most neut Tropics tend to bundle a bunch of things together most of them include some form of stimulant caffeine you can't just ingest more stimulant to be more focused it doesn't work that way most neut Tropics also include things that increase or designed to increase acetycholine things like Alpha GPC and other things of that sort and indeed there's some evidence that they can increase acetycholine so we need the focus component we need the alertness component the alertness component comes from epinephrine traditionally from caffeine stimulation the acetycholine stimulation traditionally comes from choline donors or Alpha GPC things of that sort and then you would want to have some sort of off switch because anything that's going to really stimulate your alertness that then provides a crash that crash is not a crash into the deep kind of restful Slumber that you would want for learning it's a crash into the kind of um let's just call it lopsided sleep meaning it's deep sleep but it lacks certain spindles and other elements of the physiology sleep spindles that that really engage the learning process and the reconfiguration of synapses so right now my stance on New Tropics is that maybe maybe for occasional use for provided it's safe for you I'm not recommending it but in general it tends to use more of a shotgun approach than is probably going to be useful for learning in memory in the long run okay I'd like to continue by talking about the role of temperature in sleep accessing sleep staying asleep and wakefulness temperature is super interesting as it relates to circadian rhythms and wakefulness and sleep first let's take a look at what's happening to our body temperature across each 24-hour cycle in general our temperature tends to be lowest right around 4:00 a.m. and starts creeping up around 6:00 a.m. 8: a.m. and Peaks sometime between 400 p.m. and 6: p.m. there's also an important way in which temperature matches day length in general as days get longer it tends to be hotter out not always but in general that's the way it is and as days get shorter it tends to be colder outside so temperature and day length are also linked metabolically they're linked biologically they're they're linked excuse me and atmospherically they're linked for the reasons that we talked about before about duration of day length and other climate features and so forth so one of the most powerful things about setting your circadian rhythm properly is that your temperature will start to fall into a regular rhythm and that temperature has a very strong effect on things like metabolism and when you will feel most willing and interested in exercising typically the willingness to exercise and engage in any kind of activity mental or physical is going to be when that rise in temperature is steepest when the slope of that line is greatest that's why 30 minutes after waking is one of those key Windows as well as 3 hours after waking and then when temperature actually Peaks which is generally generally about 11 hours after waking so this is why we say that temperature and cirane Rhythm are linked but they're actually even more linked than that we've talked before about how light enters the eye triggers activation of these melanops and cells which then triggers activation of the super chiasmatic nucleus the master circadian clock and then I always say the master cane clock and forms all the cells and tissues of your body and puts them into a nice cohesive Rhythm but what I've never answered was how it actually puts them into that Rhythm and it does it two ways one is it secretes a peptide a peptide is just a little protein that floats through the bloodstream and signals to the cells but the other way is it synchronizes the temperature under which those cells exist so temperature is actually the effector of the Circadian rhythm nowadays there's some interest in cold show hours and Ice baths getting into an ice bath is very interesting because you have a rebound increase in thermogenesis now you should know from the previous episode that as that temperature increases it will shift your circadian rhythm and which direction it shifts your circadian rhythm will depend on whether or not you're doing it during the daytime or late in the day if you do it after 8:00 p.m. it's going to make your day longer right because your body and your central clocks are used to temperature going up early in the day and throughout the day and peaking in the afternoon if you then increase that further or you simply increase it over its Baseline at 8 pm after temperature was already falling even if it's just by half a degree or a couple degrees or you do that with exercise doesn't have to be with the ice bath you are extending you are shifting forward you are phase delaying your clock you're convincing your clock and therefore the rest of your body that the day is still going right you you're giving it the perception the cellular and physiological perception that the day is getting longer and you will want to naturally stay up later and wake up later so for those of you that are having trouble getting up and this is going to almost sound laughable but a cold shower first thing in the morning will wake you up but that's waking you up in the short term because of a different mechanism which I'll talk about in a moment but it also is Shifting your clock it's phase advancing your clock in a way that makes you more likely to get up earlier the next day it's going to make you want to wake up about half hour to an hour earlier the next day than you normally would whereas if you do it while your temperature is falling it will tend to delay and make your body perceive as if the day is getting longer but temperature is again is not just one tool to manipulate wakeup time and circadian rhythm and Metabolism it is the effector it is the way that the central circadian clock impacts all the cells and tissues of your body light is the trigger the supermatic nucleus is the master circadian clock that mediates all these changes also in infuenced by non- photic influence like exercise and feeding and things of that sort but temperature is the effector now you can also shift your circadian rhythm with eating when you travel and you land in a new location and your schedule is inverted 12 hours one way that we know you can shift your Rhythm more quickly is to get onto the local meal schedule now that probably has to do with two effects one are changes in temperature and eating induced increases in body temperature now you should understand why that would work as well as eating has this anticipatory secretion of hyperr orexin that I talked about it earlier many people asked questions about food and neurotransmitters and how those relate to sleep wakefulness and mood which is essentially 25 hours of content for me to cover but I'm going to try and distill out the most common questions we've talked a lot about neuromodulators like dopamin aceto Coline and norepinephrine you may notice in those discussions that the precursor to say serotonin is tryptophan tryptophan actually comes from the diet it comes from the foods that we eat tyrosine is the precursor to dopamine it comes from the foods that we eat and then once we ingest them the those compounds are circulate to a variety of different cells and tissues but it is true that our food and the particular Foods we can influence things like neuromodulator levels to some extent nuts and Meats in particular red meats tend to be rich in things like tyrosine right that tells you right there that because tyrosine is the precursor of dopamine and dopamine is the precursor of norepinephrine and epinephrine that those Foods tend to lend themselves toward the production of dopamine and epinephrine and the sorts of things that are associated with wakefulness now of course the volume of food that we eat also impacts our weightfull of anything whether or not it's ribey steaks rice or cardboard please don't eat cardboard your stomach if it's very distended will draw a lot of blood into your gut and you will divert blood from other tissues and you'll become sleepy so it's not just about food content it's also about food volume all right fasting States generally are associated with more alertness epinephrine so forth and fed states are generally associated with more quiessence and relaxation serotonin and and the kind of things that lend themselves more towards sleep and less toward alertness and fed states are generally associated with more quiessence and relaxation serotonin and and the kind of things that lend themselves more towards sleep and less toward alertness there are a couple effects of food that are independent or I should say a couple effects of eating because the food won't do it when it's sitting across the table but of eating that are powerful for modulating circadian Rhythm wakefulness Etc and that's because every time we eat we get eating induced thermogenesis regardless of what we eat and now you know from the discussion about temperature that if you're eating early in the day you're tending to shift your Rhythm earlier so that you'll want to wake up earlier the next day if you're eating very late in the day even if you can fall asleep after that there's a tendency for you to want to sleep later the next day so as we finish up I just want to offer you the opportunity to do an experiment it might be interesting just a suggestion to write down for each day when you went outside to get sunlight and when you did that relative to wakings and then you might just take note of when you exercised and you might note when you might have felt chilled or cold if you do or you might have felt particularly hot or if you woke up in the middle of the night when you felt particularly hot and then the last thing you might want to do is just write down if and when you did a non-sleep deep breast protocol nsdr protocol anything that you're using to deliberately teach your nervous system how to go from more alertness to more calmness in the waking state by doing this you can start to reveal some really interesting patterns it's really about taking the patterns of behaviors of waking and light viewing and eating and exercise and superimposing that on what you're learning in this podcast and elsewhere of course and what you already know and trying to see where certain problem or problems or pain point Point might be arising maybe you start to find that using cold exposure early in the day is great for you but using it late if it's too late in the day that's not great or um if you're into the sauna or even like some people including myself if I take a hot shower or sit in a hot tub or a sauna late at night well then I get a compensatory decrease in body temperature and I sleep great provided I hydrate well enough because that can be kind of a dehydrating thing to sit in hot uh hot conditions but if I do the sauna early in the day unless I exercise immediately afterward then I tend to get the temperature drop which makes sense because we get in the sauna you're get vasodilation you throw off a lot of heat and then you generally get a compensatory drop in temperature if you do that early in the day that's right about the time that that temperature is trying to entrain the Circadian clocks of your body so I just encourage you to start becoming scientists of your own physiology of your own brain and body and seeing how the various tools that you may or may not be using are affecting your patterns of sleep your patterns of attention and wakefulness it's vitally important that if you do this that you know that it's not about trying to get onto an extremely rigid schedule it's really about trying to identify variables that are most powerful for you and that push you in the direction that you want to go and changing the variables that are pushing your body and your mind in the directions that you don't want to go self-experimentation is something that should be done slowly carefully you don't want to be Reckless about this and this is where I would say manipulating one or two variables at a time is really going to be best as opposed to changing a you know a dozen things all at once to really identify what it is that's most powerful for you and above all thank you for your interest in science [Music]