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Episode: Essentials: Using Science to Optimize Sleep, Learning & Metabolism

Author: Scicomm Media
Duration: 00:38:24

Episode Shownotes

In this Huberman Lab Essentials episode, I answer your most frequently asked questions about science-backed tools for improving alertness, enhancing learning, and achieving quality sleep. I also discuss the optimal times for exercising and eating, how to properly time light exposure, as well as methods for strategically adjusting your body

temperature to influence your nervous system. Huberman Lab Essentials are short episodes (approximately 30 minutes) focused on essential science and protocol takeaways from past Huberman Lab episodes. Essentials will be released every Thursday, and our full-length episodes will still be released every Monday. Read the full show notes for this episode at hubermanlab.com. Thank you to our sponsors AG1: https://drinkag1.com/huberman LMNT: https://drinklmnt.com/huberman Eight Sleep: https://eightsleep.com/huberman David: https://davidprotein.com/huberman Timestamps 00:00:00 Introduction to Huberman Lab Essentials 00:00:37 Understanding Circadian Rhythms & Light 00:02:17 Impact of Red Light on Circadian Rhythms 00:03:12 Light Through Windows & Circadian Clocks 00:05:04 Seasonal Changes & Circadian Rhythms 00:07:38 Neurotransmitters & Mood Regulation 00:09:00 Sponsors: LMNT & Eight Sleep 00:11:47 Exercise & Circadian Rhythms 00:14:40 Neuroplasticity & Learning 00:20:16 Sponsor: AG1 00:21:49 Non-Sleep Deep Rest (NSDR) & Learning 00:23:43 Nootropics & Cognitive Enhancement 00:26:16 Temperature & Circadian Rhythms 00:31:25 Sponsor: David 00:32:41 Food, Neurotransmitters & Circadian Rhythms 00:35:28 Self-Experimentation & Conclusion Disclaimer & Disclosures

Summary

In this episode of the Huberman Lab podcast, Dr. Andrew Huberman explores strategies grounded in science to optimize sleep, learning, and metabolism. Key topics include the impact of different light sources on circadian rhythms, the timing and type of exercise regarding sleep quality, and the roles of neurotransmitters like acetylcholine and epinephrine in cognitive enhancement. Additionally, the podcast addresses nootropics, the effects of body temperature, and meal timing on these biological cycles, emphasizing the importance of self-experimentation to discover personalized optimization strategies for health and performance.

Go to PodExtra AI's episode page (Essentials: Using Science to Optimize Sleep, Learning & Metabolism) to play and view complete AI-processed content: summary, mindmap, topics, takeaways, transcript, keywords and highlights.

Full Transcript

00:00:00 Speaker_00
Welcome to Huberman Lab Essentials, where we revisit past episodes for the most potent and actionable science-based tools for mental health, physical health, and performance.

00:00:12 Speaker_00
I'm Andrew Huberman, and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine. Today is episode three of the podcast, and it is office hours.

00:00:21 Speaker_00
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 and detail.

00:00:37 Speaker_00
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?

00:00:53 Speaker_00
Will a fire in my fireplace or using candlelight be too much light? Great question.

00:00:59 Speaker_00
Turns out that moonlight, candlelight, 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.

00:01:14 Speaker_00
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,

00:01:24 Speaker_00
is that these neurons in your eye that I discussed in the previous episode, these melanopsin ganglion cells, also called intrinsically photosensitive ganglion cells, those cells adjust their sensitivity across the day.

00:01:38 Speaker_00
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.

00:01:48 Speaker_00
But those cells adjust their sensitivity such that they will not activate the triggers in the brain that convey daytime signals when they view moonlight, even a full moon, a really bright moon or fire.

00:02:04 Speaker_00
Because we talked about just how crucial it is to avoid bright lights between the hours of about 10 PM and 4 AM, except when you need to view things for sake of safety or work and so forth. I also received a lot of questions about red light.

00:02:20 Speaker_00
In principle, red light will not stimulate the melanopsin retinal neurons that wake up the brain and circadian clock and signal daytime.

00:02:30 Speaker_00
However, most of the red lights, in particular, the red lights that come on these sheets of these products that people are supposed to view them in order to

00:02:38 Speaker_00
access a number of health effects, those are way too bright and would definitely wake up your body and brain.

00:02:45 Speaker_00
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.

00:02:58 Speaker_00
Now, do you need red lights?

00:02:59 Speaker_00
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.

00:03:11 Speaker_00
Okay, a huge number of people asked me about light through windows. 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,

00:03:25 Speaker_00
You can have a bright day outside or some sunlight, hold up that app, take a picture. It'll tell you how many Lux are in that environment. Now close the window.

00:03:33 Speaker_00
And if you want close the screen or don't open the screen, you can do all sorts of experiments. And you'll see that it will at least half the amount of Lux. And it doesn't scale linearly.

00:03:42 Speaker_00
Meaning let's say I get a 10,000 Lux outside, 5,000 looking out through an open window. And then I close the window and it's 2,500 Lux. It does not mean that you just need to view that sunlight for twice as long if it's half as many lux, okay?

00:03:59 Speaker_00
It's not like 2,500 lux means you need to look for 10 minutes and 5,000 lux means you look for five 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.

00:04:13 Speaker_00
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.

00:04:20 Speaker_00
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.

00:04:30 Speaker_00
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.

00:04:37 Speaker_00
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.

00:04:49 Speaker_00
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.

00:05:04 Speaker_00
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.

00:05:16 Speaker_00
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 that sun.

00:05:32 Speaker_00
The earth is tilted, it's not perfectly upright. So the earth is tilted on its axis.

00:05:39 Speaker_00
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.

00:05:52 Speaker_00
If you're 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.

00:06:02 Speaker_00
And you're also going to experience some very short days, depending on which pole you're at and what time of year it is. A simple way to put this is depending on time of year, the days are either getting shorter or getting longer.

00:06:13 Speaker_00
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 inhibits melatonin powerfully.

00:06:33 Speaker_00
If days are long and getting longer, that means melatonin is reduced. If days are getting shorter, that melatonin signal is getting longer.

00:06:45 Speaker_00
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.

00:06:54 Speaker_00
by understanding that light and extended day length inhibit melatonin, and melatonin tends to be associated with a more depressed or reduced functioning of these kind of activity driving and 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 adjustments that if you're feeling low, you might ask, how much light am I getting?

00:07:22 Speaker_00
When am I getting that light? because sleep is also important for restoring mood, right? So you need sleep.

00:07:28 Speaker_00
You can't just, you know, 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.

00:07:43 Speaker_00
Serotonin is a neurotransmitter that is associated with feelings of wellbeing provided it's at proper levels.

00:07:50 Speaker_00
but well-being of a particular kind, well-being associated with quiescence and calm and the feeling that we have enough resources in our immediate kind of conditions.

00:08:00 Speaker_00
It's the kind of thing that comes from a good meal or sitting down with friends or holding a loved one or conversing with somebody that you really bond with. Serotonin does not stimulate action. It tends to stimulate stillness.

00:08:16 Speaker_00
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.

00:08:30 Speaker_00
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.

00:08:45 Speaker_00
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 and memory and mood.

00:08:55 Speaker_00
That's one powerful reason to avoid bright light in the middle of the night. I'd like to take a quick break and thank one of our sponsors, Element. Element is an electrolyte drink that has everything you need and nothing you don't.

00:09:08 Speaker_00
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00:09:17 Speaker_00
In fact, even a slight degree of dehydration can diminish your cognitive and physical performance to a considerable degree. It's also important that you're not just hydrated, but that you get adequate amounts of electrolytes in the right ratios.

00:09:29 Speaker_00
Drinking a packet of Element dissolved in water makes it very easy to ensure that you're getting adequate amounts of hydration and electrolytes.

00:09:36 Speaker_00
To make sure that I'm getting proper amounts of both, I dissolve one packet of Element in about 16 to 32 ounces of water when I wake up in the morning, and I drink that basically first thing in the morning.

00:09:46 Speaker_00
I'll also drink a packet of Element 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.

00:09:54 Speaker_00
There are a bunch of different great tasting flavors of Element. I like the watermelon, I like the raspberry, I like the citrus. Basically, I like all of them.

00:10:01 Speaker_00
If you'd like to try Element, you can go to drinkelement.com slash Huberman to claim an Element sample pack with the purchase of any Element drink mix. Again, that's drinkelement spelled L-M-N-T.

00:10:12 Speaker_00
So it's drinkelement.com slash Huberman to claim a free sample pack. Today's episode is also brought to us by Eight Sleep. Eight Sleep makes smart mattress covers with cooling, heating, and sleep tracking capacity.

00:10:24 Speaker_00
Now, I've spoken before on this podcast about the critical need for us to get adequate amounts of quality sleep each night.

00:10:29 Speaker_00
Now, one of the best ways to ensure a great night's sleep is to ensure that the temperature of your sleeping environment is correct.

00:10:35 Speaker_00
And that's because in order to fall and stay deeply asleep, your body temperature actually has to drop by about one to three degrees.

00:10:41 Speaker_00
And in order to wake up feeling refreshed and energized, your body temperature actually has to increase about one to three degrees.

00:10:48 Speaker_00
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00:10:57 Speaker_00
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00:11:09 Speaker_00
The Pod 4 Ultra has improved cooling and heating capacity. I find that very useful because I like to make the bed really cool at the beginning of the night, even colder in the middle of the night. warm as I wake up.

00:11:20 Speaker_00
That's what gives me the most slow wave sleep and rapid eye movement sleep. If you'd like to try an Eight Sleep mattress cover, you can go to eightsleep.com slash Huberman to access their Black Friday offer right now.

00:11:31 Speaker_00
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00:11:43 Speaker_00
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00:11:46 Speaker_00
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.

00:12:01 Speaker_00
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.

00:12:08 Speaker_00
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?

00:12:20 Speaker_00
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.

00:12:30 Speaker_00
Epinephrine and adrenaline are basically the same thing and they tend to stimulate agitation and the desire to move. I got a lot of questions about exercise. What forms of exercise are best? for sleeping well, when should I exercise, et cetera.

00:12:44 Speaker_00
There are basically two forms of exercise that we can talk about. Although of course I realized there are many different forms of exercise.

00:12:50 Speaker_00
There's much more nuance to this, but we can talk about cardiovascular exercise where the idea is to repeat a movement over and over and over continuously. So that'd be like running, biking, rowing, cycling, this kind of thing.

00:13:01 Speaker_00
or there's a resistance exercise where you're moving, lifting, presumably putting down also things of progressively heavier and heavier weight that you couldn't do continuously for 30 minutes.

00:13:15 Speaker_00
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.

00:13:25 Speaker_00
I think there are, however, a couple of windows that the exercise science literature and the circadian literature points to as windows related to body temperature in which performance, injury, in which performance is optimized, injury is reduced, and so on.

00:13:43 Speaker_00
And those tend to be 30 minutes after waking. three 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.

00:13:58 Speaker_00
Last time we talked about non-photic phase shifts. If you exercise first thing in the morning, your body will start to develop an anticipatory circuit.

00:14:07 Speaker_00
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 three or four days.

00:14:15 Speaker_00
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 wake up signal to the brain and body. So you might want to think about that.

00:14:28 Speaker_00
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.

00:14:39 Speaker_00
Many of your questions were about neural plasticity, which is the brain and nervous system's ability to change in response to experience.

00:14:48 Speaker_00
There was a question that asked whether or not these really deep biological mechanisms around wakefulness, time of waking, sleep, et cetera, were subject to neuroplasticity. And indeed they are.

00:14:59 Speaker_00
Some of that plasticity is short-term and some of it is more long-term. 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 a.m., noon, and 7 p.m.

00:15:15 Speaker_00
is when you eat your food, not suggesting you do this, but let's say you were to do that for a couple of days.

00:15:20 Speaker_00
After a few days, you would start to anticipate those mealtimes where no matter where you were in the world, no matter what was going on in your life, about five to 10 minutes before those mealtimes, you would start to feel hungry and even a little agitated, which is your body's way of trying to get you to forage for food.

00:15:39 Speaker_00
And that's because of some peptide signals that come from the periphery from your body, things like hypocretin, orexin, that signal to the hypothalamus and brainstem to make you active and alert and look for food and feel hungry.

00:15:53 Speaker_00
So there's kind of an anticipatory circuit

00:15:56 Speaker_00
that's a chemical circuit, but eventually over time, the neurons, the neural circuits that control hypocretinorexin 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.

00:16:15 Speaker_00
The same thing is true for these waking and exercise and other schedules, including ultradian schedules.

00:16:21 Speaker_00
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.

00:16:39 Speaker_00
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.

00:16:54 Speaker_00
That's the beauty of neural plasticity. A number of people asked, what can I do to increase plasticity? And that really comes in two forms.

00:17:03 Speaker_00
There's plasticity that we can access in sleep to improve rates of learning and depth of learning from the previous day or so.

00:17:13 Speaker_00
And there's this NSDR non-sleep deep rest that can be done without sleeping to improve rates of learning and depth of retention, et cetera. So let's consider those both. And you can incorporate these protocols if you like.

00:17:25 Speaker_00
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.

00:17:39 Speaker_00
Matt Walker also talks about some of these studies 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, does a spatial memory task.

00:17:54 Speaker_00
So there tends to be a screen with a bunch of different objects popping up on the screen in different locations. So it might be a bulldog There might be a cat, then it might be an apple, then it might be a pen in different locations.

00:18:07 Speaker_00
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.

00:18:20 Speaker_00
If you had enough objects and change the locations enough, this can actually be quite difficult.

00:18:25 Speaker_00
In this study, the subjects either just went through the experiment or a particular odor was released into the room while they were learning, or a tone was played in the room while they were learning.

00:18:40 Speaker_00
And then during the sleep of those subjects, the following night and the following night, this was done repeatedly for several nights,

00:18:50 Speaker_00
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 if they if the subjects had the odor but not the tone they had they did it with putting the tone

00:19:11 Speaker_00
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

00:19:31 Speaker_00
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.

00:19:42 Speaker_00
What this means that you can cue the subconscious brain, the asleep brain to learn particular things better. and faster. So how might you implement this? Well, you could play with this if you want.

00:19:54 Speaker_00
I don't see any real challenge to this provided the odor is a safe one and it doesn't wake you up and the tone is a safe one and doesn't wake you up.

00:20:04 Speaker_00
You could do this by having a metronome, for instance, while I'm learning something, playing in the background or particular music, and then have that very faintly while you sleep. So you could apply this if you like and try this.

00:20:16 Speaker_00
I'd like to take a quick break and acknowledge our sponsor, AG1. AG1 is a vitamin mineral probiotic drink that includes prebiotics and adaptogens. I've been drinking AG1 since 2012, and I started doing it at a time when my budget was really limited.

00:20:30 Speaker_00
In fact, I only had enough money to purchase one supplement, and I'm so glad that I made that supplement AG1.

00:20:36 Speaker_00
The reason for that is even though I strive to eat whole foods and unprocessed foods, it's very difficult to get enough vitamins and minerals, micronutrients, and adaptogens from diet alone in order to make sure that I'm at my best, meaning have enough energy for all the activities I participate in from morning until night, sleeping well at night, and keeping my immune system strong.

00:20:54 Speaker_00
When I take AG1 daily, I find that all aspects of my health, my physical health, my mental health, my performance, recovery from exercise, all of those improve.

00:21:03 Speaker_00
And I know that because I've had lapses when I didn't take my AG1 and I certainly felt the difference.

00:21:07 Speaker_00
I also noticed, and this makes perfect sense given the relationship between the gut microbiome and the brain, that when I regularly take AG1, that I have more mental clarity and more mental energy.

00:21:17 Speaker_00
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00:21:23 Speaker_00
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00:21:37 Speaker_00
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00:21:49 Speaker_00
The other form of neuroplasticity is not the neuroplasticity that you're amplifying by listening to tones or smelling odors in sleep, but the neuroplasticity that you can access with non-sleep deep rest. So NSDR, non-sleep deep rest,

00:22:05 Speaker_00
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.

00:22:16 Speaker_00
NSDR has been shown to increase rates of learning when done for 20 minute bouts to match an approximately 90 minute bout of learning. So what am I talking about? 90 minute, Cycles are these ultradian cycles that I've talked about previously.

00:22:34 Speaker_00
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 learning feels almost like agitation and strain.

00:22:47 Speaker_00
And then by the end of that 90 minute cycle, it becomes very hard to maintain focus and learn more information.

00:22:54 Speaker_00
There's a study published in Cell Reports last year, great journal, excellent paper showing that 20 minute naps or light sleep of the sort of non-sleep deep rest taken immediately after or close to, it doesn't have to be immediately after you finished the last sentence of learning or whatever it is or bar of music.

00:23:15 Speaker_00
But, you know, a couple of minutes after transitioning to a period 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.

00:23:30 Speaker_00
So that's pretty cool because this is a cost-free, drug-free way of accelerating learning without having to get more sleep, but simply by introducing these 20 minute bouts.

00:23:43 Speaker_00
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 nootropics, AKA smart drugs.

00:23:58 Speaker_00
Ah, this is a big topic. That sigh was a sigh of concern about how to address nootropics in a thorough enough, but thoughtful enough way. There are elements to learning that we've discussed here before that are very concrete.

00:24:13 Speaker_00
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.

00:24:21 Speaker_00
right, distractions about things you should be doing, could be doing, or might be doing, and focus on what you need to do.

00:24:27 Speaker_00
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 nootropic allows you to bypass the need for sleep and deep rest.

00:24:42 Speaker_00
That's important to understand. Right now, most nootropics 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.

00:24:55 Speaker_00
Most nootropics also include things that increase or are designed to increase acetylcholine, things like alpha-GPC and other things of that sort. And indeed, there's some evidence that they can increase acetylcholine. So we need the focus component.

00:25:10 Speaker_00
We need the alertness component. The alertness component comes from epinephrine, traditionally from caffeine stimulation. The acetylcholine stimulation traditionally comes from choline donors or alpha GPC, things of that sort.

00:25:22 Speaker_00
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.

00:25:37 Speaker_00
It's a crash into the kind of, 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 really engage the learning process and the reconfiguration of synapses.

00:25:54 Speaker_00
So right now, my stance on nootropics is that maybe, maybe for occasional use,

00:26:03 Speaker_00
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 and memory in the long run.

00:26:15 Speaker_00
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.

00:26:30 Speaker_00
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 a.m. and starts creeping up around 6 a.m., 8 a.m., and peaks sometime between 4 p.m.

00:26:49 Speaker_00
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.

00:27:04 Speaker_00
So temperature and day length are also linked. Metabolically, they're linked. Biologically, they're linked, excuse me.

00:27:12 Speaker_00
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.

00:27:20 Speaker_00
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.

00:27:28 Speaker_00
And that temperature has a very strong effect on things like metabolism and when you will feel most willing and interested in exercising.

00:27:38 Speaker_00
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.

00:27:48 Speaker_00
That's why 30 minutes after waking is one of those key windows, as well as three hours after waking, and then when temperature actually peaks, which is generally, generally about 11 hours after waking. So,

00:28:01 Speaker_00
This is why we say that temperature and circadian rhythm are linked, but they're actually even more linked than that.

00:28:08 Speaker_00
We've talked before about how light enters the eye, triggers activation of these melanopsin cells, which then triggers activation of the suprachiasmatic nucleus, the master circadian clock.

00:28:17 Speaker_00
And then I always say the master circadian clock informs 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.

00:28:31 Speaker_00
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.

00:28:42 Speaker_00
So temperature is actually the effector of the circadian rhythm. Nowadays, there's some interest in cold showers and ice baths. Getting into an ice bath is very interesting because you have a rebound increase in thermogenesis.

00:28:56 Speaker_00
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.

00:29:07 Speaker_00
If you do it after 8 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.

00:29:21 Speaker_00
If you then increase that further, or you simply increase it over its baseline at 8 p.m.

00:29:27 Speaker_00
after temperature was already falling, even if it's just by a 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

00:29:41 Speaker_00
and therefore the rest of your body, that the day is still going, right? 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.

00:29:54 Speaker_00
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,

00:30:10 Speaker_00
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.

00:30:20 Speaker_00
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 wake up time and circadian rhythm and metabolism.

00:30:36 Speaker_00
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 suprachiasmatic nucleus is the master circadian clock that mediates all these changes.

00:30:48 Speaker_00
Also influenced 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.

00:30:59 Speaker_00
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.

00:31:12 Speaker_00
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 hypocretin orexin that I talked about earlier.

00:31:25 Speaker_00
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00:31:36 Speaker_00
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00:31:48 Speaker_00
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00:31:56 Speaker_00
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00:32:04 Speaker_00
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00:32:17 Speaker_00
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00:32:23 Speaker_00
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00:32:36 Speaker_00
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00:32:41 Speaker_00
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.

00:32:57 Speaker_00
We've talked a lot about neuromodulators like dopamine, acetylcholine, and norepinephrine. You may notice in those discussions that the precursors to say serotonin is tryptophan. Tryptophan actually comes from the diet.

00:33:09 Speaker_00
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, those compounds circulate to a variety of different cells and tissues.

00:33:25 Speaker_00
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?

00:33:39 Speaker_00
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.

00:33:58 Speaker_00
Now, of course, the volume of food that we eat also impacts our wakefulness.

00:34:02 Speaker_00
If we eat a lot of anything, whether or not it's ribeye 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.

00:34:17 Speaker_00
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 and so forth.

00:34:28 Speaker_00
And fed states are generally associated with more quiescence and relaxation, serotonin and the kind of things that lend themselves more towards sleep and less toward alertness.

00:34:40 Speaker_00
And fed states are generally associated with more quiescence and relaxation, serotonin and the kind of things that lend themselves more towards sleep and less toward alertness.

00:34:52 Speaker_00
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, et cetera.

00:35:07 Speaker_00
And that's because every time we eat, we get eating induced thermogenesis, regardless of what we eat.

00:35:12 Speaker_00
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.

00:35:21 Speaker_00
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.

00:35:33 Speaker_00
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.

00:35:44 Speaker_00
And then you might just take note of when you exercised and you might note when you might've felt chilled or cold, if you do, or you might've felt particularly hot. or if you woke up in the middle of the night when you felt particularly hot.

00:35:57 Speaker_00
And then the last thing you might want to do is just write down if and when you did a non-sleep deep rest 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.

00:36:13 Speaker_00
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.

00:36:24 Speaker_00
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 problems or pain points might be arising.

00:36:35 Speaker_00
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.

00:36:44 Speaker_00
Or 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,

00:36:53 Speaker_00
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 conditions.

00:37:02 Speaker_00
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 can get in the sauna, you get vasodilation, you throw off a lot of heat, and then you generally get a compensatory drop in temperature.

00:37:16 Speaker_00
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.

00:37:22 Speaker_00
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.

00:37:32 Speaker_00
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.

00:37:46 Speaker_00
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. changing the variables that are pushing your body and your mind in the directions that you don't want to go.

00:37:58 Speaker_00
Self-experimentation is something that should be done slowly, carefully. You don't wanna be reckless about this.

00:38:04 Speaker_00
And this is where I would say manipulating one or two variables at a time is really gonna be best as opposed to changing a dozen things all at once to really identify what it is that's most powerful for you.

00:38:16 Speaker_00
And above all, thank you for your interest in science.