Essentials: Using Science to Optimize Sleep, Learning & Metabolism

00:00:00.000 | - Welcome to Huberman Lab Essentials,

00:00:02.320 | where we revisit past episodes

00:00:04.380 | for the most potent and actionable science-based tools

00:00:07.560 | for mental health, physical health, and performance.

00:00:10.320 | I'm Andrew Huberman,

00:00:12.880 | and I'm a professor of neurobiology and ophthalmology

00:00:15.520 | at Stanford School of Medicine.

00:00:17.280 | Today is episode three of the podcast,

00:00:19.340 | and it is office hours.

00:00:20.960 | Office hours, as many of you know,

00:00:23.160 | it's where students come to the office of the professor,

00:00:25.960 | sit down and ask questions,

00:00:27.920 | requesting clarification about things that were confusing,

00:00:31.200 | or to simply go down the route

00:00:33.760 | of exploring a topic with more depth and detail.

00:00:37.120 | Somebody asked,

00:00:39.080 | "What is the role of moonlight and fire?"

00:00:43.040 | I'm presuming they mean fireplace or candle

00:00:45.880 | or things of that sort.

00:00:47.240 | "In setting circadian rhythms,

00:00:49.360 | is it okay to view moonlight at night,

00:00:52.160 | or will that wake me up?

00:00:53.560 | Will a fire in my fireplace or using candlelight

00:00:57.120 | be too much light?"

00:00:58.720 | Great question.

00:00:59.880 | Turns out that moonlight, candlelight,

00:01:03.480 | and even a fireplace,

00:01:04.780 | if you have one of these roaring fires

00:01:06.160 | going in the fireplace,

00:01:07.880 | do not reset your circadian clock at night

00:01:11.280 | and trick your brain into thinking that it's morning.

00:01:14.240 | Even though, if you've ever sat close to a fireplace

00:01:17.200 | or even a candle, that light seems very bright.

00:01:20.240 | And there are two reasons for that that are very important.

00:01:23.060 | The first one is that these neurons in your eye

00:01:26.480 | that I discussed in the previous episode,

00:01:28.240 | these melanopsin ganglion cells,

00:01:30.840 | also called intrinsically photosensitive ganglion cells,

00:01:34.120 | those cells adjust their sensitivity across the day.

00:01:38.140 | And those cells respond best to the blue-yellow contrast

00:01:41.480 | present in the rising and setting sun,

00:01:44.000 | so-called low solar angle sun,

00:01:45.920 | also discussed in the previous episode.

00:01:48.160 | But those cells adjust their sensitivity

00:01:50.600 | such that they will not activate the triggers in the brain

00:01:55.960 | that convey daytime signals when they view moonlight,

00:02:00.960 | even a full moon, a really bright moon, or fire,

00:02:04.680 | because we talked about just how crucial it is

00:02:07.120 | to avoid bright lights

00:02:08.160 | between the hours of about 10 p.m. and 4 a.m.,

00:02:11.120 | except when you need to view things for sake of safety

00:02:14.760 | or work and so forth.

00:02:17.880 | I also received a lot of questions about red light.

00:02:20.300 | In principle, red light will not stimulate the melanopsin

00:02:24.840 | retinal neurons that wake up the brain and circadian clock

00:02:28.240 | and signal daytime.

00:02:30.040 | However, most of the red lights,

00:02:31.520 | in particular the red lights that come on these sheets

00:02:33.680 | or these products that people are supposed to view

00:02:36.400 | in order to access a number of health effects,

00:02:40.360 | those are way too bright

00:02:42.040 | and would definitely wake up your body and brain.

00:02:45.040 | So if you're thinking about red light

00:02:46.520 | for sake of avoiding the negative effects of light

00:02:49.360 | later in the day and at night,

00:02:51.320 | then you want that red light to be very, very dim,

00:02:53.720 | certainly much dimmer than is

00:02:55.720 | on most of those commercial products.

00:02:58.160 | Now, do you need red lights?

00:02:59.680 | No, although red lights are rather convenient

00:03:01.640 | because you can see pretty well with them on,

00:03:03.880 | but if they're dim, they won't wake up the circadian clock,

00:03:06.780 | they won't have this dopamine disrupting thing

00:03:09.360 | that we talked about in the previous podcast.

00:03:11.200 | Okay, a huge number of people asked me

00:03:14.420 | about light through windows.

00:03:16.920 | Setting your circadian clock

00:03:18.680 | with sunlight coming through a window

00:03:20.420 | is going to take 50 to 100 times longer.

00:03:22.600 | You can download the free app, Light Meter.

00:03:25.160 | You can have a bright day outside or some sunlight,

00:03:27.640 | hold up that app, take a picture.

00:03:29.400 | It'll tell you how many lux are in that environment.

00:03:31.780 | Now close the window.

00:03:33.240 | And if you want, close the screen or don't open the screen.

00:03:35.280 | You can do all sorts of experiments.

00:03:36.360 | You'll see that it will at least half the amount of lux.

00:03:40.040 | And it doesn't scale linearly,

00:03:42.440 | meaning let's say I get 10,000 lux outside,

00:03:47.000 | 5,000 looking out through an open window,

00:03:49.080 | and then I close the window and it's 2,500 lux.

00:03:51.920 | It does not mean that you just need to view that sunlight

00:03:54.520 | for twice as long if it's half as many lux, okay?

00:03:59.160 | It's not like 2,500 lux means you need to look

00:04:02.640 | for 10 minutes and 5,000 lux means you look for five minutes.

00:04:06.720 | It doesn't scale that way

00:04:08.320 | just because the biology doesn't work that way.

00:04:10.660 | Best thing to do is to get outside if you can.

00:04:13.120 | If you can't, next best thing to do

00:04:14.620 | is to keep that window open.

00:04:16.240 | It is perfectly fine to wear prescription lenses

00:04:18.800 | and contacts.

00:04:20.240 | Why is it okay to wear prescription lenses and contacts

00:04:22.680 | when those are glass also,

00:04:24.480 | but looking through a window diminishes the effect?

00:04:28.520 | Well, we should think about this.

00:04:30.200 | The lenses that you wear in front of your eyes

00:04:32.460 | by prescription or on your eyes are designed

00:04:34.400 | to focus the light onto your neural retina.

00:04:36.920 | So let's think about why I'm making

00:04:39.660 | some of these recommendations

00:04:40.920 | because I think it can really empower you

00:04:44.340 | with the ability to change your behavior

00:04:47.240 | in terms of light viewing and other things,

00:04:49.880 | depending on time of year,

00:04:51.640 | depending on other lifestyle factors.

00:04:55.440 | The important point to understand is that early in the day,

00:04:58.320 | your central circadian clocks and all these mechanisms

00:05:01.560 | are looking for a lot of light.

00:05:04.140 | Okay, I want to talk about seasonal changes

00:05:07.520 | in all these things as they relate to mood and metabolism.

00:05:11.560 | So as all of you know,

00:05:13.100 | the earth spins once every 24 hours on its axis.

00:05:16.840 | So part of that day we're bathed in sunlight,

00:05:18.800 | depending on where we are.

00:05:19.620 | The other half of the day or part of the day

00:05:21.240 | we're in darkness.

00:05:22.580 | The earth also travels around the sun.

00:05:24.720 | 365 days is the time that it takes one year

00:05:29.120 | to travel around that sun.

00:05:30.620 | The earth is tilted.

00:05:33.820 | It's not perfectly upright.

00:05:36.880 | So the earth is tilted on its axis.

00:05:39.920 | So depending on where we are in that 365 day journey,

00:05:43.500 | and depending on where we are in terms of hemisphere,

00:05:45.380 | Northern hemisphere, Southern hemisphere,

00:05:47.500 | some days of the year are longer than others.

00:05:50.960 | Some are very short, some are very long.

00:05:52.880 | If you're at the equator,

00:05:54.760 | you experience less variation in day length

00:05:56.840 | and therefore night length.

00:05:57.920 | And if you're closer to the poles,

00:05:59.640 | you're going to experience some very long days.

00:06:02.500 | And you're also going to experience some very short days,

00:06:05.120 | depending on which pole you're at

00:06:06.640 | and what time of year it is.

00:06:08.320 | A simple way to put this is depending on time of year,

00:06:10.640 | the days are either getting shorter or getting longer.

00:06:12.960 | Now, every cell in your body adjusts its biology

00:06:17.100 | according to day length,

00:06:18.680 | except your brain body and cells

00:06:22.880 | don't actually know anything about day length.

00:06:25.540 | It only knows night length.

00:06:27.680 | And here's how it works.

00:06:28.960 | Light inhibits melatonin powerfully.

00:06:31.660 | If days are long and getting longer,

00:06:36.480 | that means melatonin is reduced.

00:06:40.080 | If days are getting shorter,

00:06:42.360 | that melatonin signal is getting longer.

00:06:45.800 | So every cell in your body actually knows external day length

00:06:49.800 | and therefore time of year

00:06:51.740 | by way of the duration of the melatonin signal.

00:06:54.420 | By understanding that light and extended day length

00:06:57.620 | inhibit melatonin and melatonin tends to be associated

00:07:00.940 | with a more depressed or reduced functioning

00:07:03.420 | of these kind of activity driving and mood elevating signals

00:07:08.060 | and understanding that you have some control over melatonin

00:07:11.420 | by way of light, including sunlight,

00:07:13.500 | but also artificial light that should empower you,

00:07:16.020 | I believe, to make the adjustments

00:07:17.860 | that if you're feeling low, you might ask,

00:07:21.540 | how much light am I getting?

00:07:22.500 | When am I getting that light?

00:07:24.140 | Because sleep is also important for restoring mood, right?

00:07:27.500 | So you need sleep.

00:07:28.340 | You can't just, you know,

00:07:29.420 | just crush melatonin across the board

00:07:32.460 | and expect to feel good

00:07:33.620 | because then you're not going to fall asleep

00:07:34.800 | and stay asleep.

00:07:35.640 | Melatonin, not incidentally, comes from,

00:07:40.500 | is synthesized from serotonin.

00:07:43.260 | Serotonin is a neurotransmitter that is associated

00:07:46.340 | with feelings of wellbeing provided to proper levels,

00:07:50.020 | but wellbeing of a particular kind,

00:07:52.020 | wellbeing associated with quiescence and calm

00:07:55.940 | and the feeling that we have enough resources

00:07:58.420 | in our immediate kind of conditions.

00:08:00.660 | It's the kind of thing that comes from a good meal

00:08:02.720 | or sitting down with friends or holding a loved one

00:08:05.780 | or conversing with somebody that you really bond with.

00:08:10.300 | Serotonin does not stimulate action.

00:08:13.300 | It tends to stimulate stillness.

00:08:16.200 | Very different than the neuromodulator dopamine,

00:08:18.880 | which is a reward, feel-good neuromodulator

00:08:21.740 | that stimulates action.

00:08:23.300 | And actually dopamine is the precursor to epinephrine,

00:08:28.300 | to adrenaline, which actually puts us into action.

00:08:30.900 | It's actually made from dopamine, right?

00:08:34.020 | So you can start to think about light as a signal

00:08:37.620 | that is very powerful for modulating things

00:08:40.140 | like sleep and wakefulness,

00:08:41.220 | but also serotonin levels, melatonin levels.

00:08:45.100 | And I talked about this previously,

00:08:46.840 | but I'll mention once more

00:08:47.680 | that light in the middle of the night reduces dopamine levels

00:08:50.540 | to the point where it can start causing problems

00:08:53.060 | with learning and memory and mood.

00:08:55.220 | That's one powerful reason to avoid bright light

00:08:58.340 | in the middle of the night.

00:08:59.760 | Throughout this podcast and in previous episodes,

00:09:01.960 | I've been mentioning neuromodulators,

00:09:03.820 | things like serotonin and dopamine,

00:09:06.360 | which tend to bias certain brain circuits

00:09:09.380 | and things in our body to happen

00:09:11.020 | and certain brain circuits

00:09:12.060 | and things in our body not to happen.

00:09:14.360 | One of the ones I've mentioned numerous times is epinephrine,

00:09:17.060 | which is a neuromodulator that tends to put us into action,

00:09:20.060 | make us want to move.

00:09:21.580 | In fact, when it's released in high amounts

00:09:23.460 | in our brain and body,

00:09:24.320 | it can lead to what we call stress

00:09:26.260 | or the feeling of being stressed.

00:09:27.960 | Several people ask me,

00:09:29.900 | what's the difference between epinephrine and adrenaline?

00:09:33.380 | Adrenaline is secreted from the adrenal glands,

00:09:35.980 | which sit right above our kidneys.

00:09:37.940 | Epinephrine is the exact same molecule,

00:09:41.140 | except that it's released within the brain.

00:09:43.580 | Epinephrine and adrenaline are basically the same thing

00:09:45.660 | and they tend to stimulate agitation

00:09:47.860 | and the desire to move.

00:09:49.620 | Got a lot of questions about exercise.

00:09:52.020 | What forms of exercise are best for sleeping well?

00:09:55.660 | When should I exercise, et cetera?

00:09:57.640 | There are basically two forms of exercise

00:09:59.660 | that we can talk about.

00:10:00.500 | Although, of course,

00:10:01.320 | I realize there are many different forms of exercise.

00:10:03.500 | There's much more nuance to this,

00:10:04.780 | but we can talk about cardiovascular exercise

00:10:07.020 | where the idea is to repeat a movement

00:10:09.060 | over and over and over continuously.

00:10:10.560 | So that'd be like running, biking, rowing, cycling,

00:10:12.940 | this kind of thing.

00:10:14.420 | Or there's a resistance exercise where you're moving,

00:10:19.300 | lifting, presumably putting down also,

00:10:22.060 | things of progressively heavier and heavier weight

00:10:24.820 | that you couldn't do continuously for 30 minutes.

00:10:28.300 | Now you will see some places,

00:10:29.740 | aerobic exercise is best done in the morning

00:10:31.700 | and weight training is best done in the afternoon.

00:10:34.180 | I think there's far more individual variation than that.

00:10:37.220 | I think there are, however, a couple of windows

00:10:41.140 | that the exercise science literature

00:10:43.100 | and the circadian literature points to

00:10:45.140 | as windows related to body temperature

00:10:47.860 | in which performance, injury,

00:10:50.740 | in which performance is optimized,

00:10:53.500 | injury is reduced, and so on.

00:10:56.600 | And those tend to be 30 minutes after waking,

00:11:00.540 | three hours after waking,

00:11:02.300 | and the later afternoon, usually 11 hours after waking,

00:11:06.460 | which is when temperature tends to peak.

00:11:08.980 | A note about working out first thing in the morning.

00:11:11.620 | Last time we talked about non-photic phase shifts.

00:11:14.060 | If you exercise first thing in the morning,

00:11:16.900 | your body will start to develop an anticipatory circuit.

00:11:20.140 | There's actually plasticity in these circadian circuits

00:11:22.820 | that will lead you to want to wake up

00:11:25.300 | at the particular time that you exercised

00:11:27.060 | the previous three or four days.

00:11:28.700 | So that can be a powerful tool,

00:11:30.260 | but you still want to get light exposure

00:11:32.380 | because it turns out that light and exercise converge

00:11:35.700 | to give an even bigger wake-up signal to the brain and body.

00:11:39.900 | So you might want to think about that.

00:11:41.700 | Some people find if they exercise late in the day,

00:11:43.940 | they have trouble sleeping.

00:11:45.580 | In general, intense exercise does that,

00:11:49.540 | whereas the kind of lower intensity exercise doesn't.

00:11:52.620 | Many of your questions were about neural plasticity,

00:11:55.460 | which is the brain and nervous system's ability to change

00:11:58.340 | in response to experience.

00:11:59.940 | There was a question that asked whether or not

00:12:03.340 | these really deep biological mechanisms

00:12:05.820 | around wakefulness, time of waking, sleep, et cetera,

00:12:09.300 | were subject to neural plasticity, and indeed they are.

00:12:12.720 | Some of that plasticity is short-term

00:12:14.580 | and some of it is more long-term.

00:12:16.900 | There's a really good analogy here,

00:12:18.220 | which is if you happen to eat on a very tight schedule

00:12:23.220 | where every day, say at 8 a.m., noon, and 7 p.m.

00:12:28.020 | is when you eat your food, not suggesting you do this,

00:12:30.100 | but let's say you were to do that for a couple days.

00:12:33.380 | After a few days, you would start to anticipate

00:12:36.100 | those mealtimes where no matter where you were in the world,

00:12:40.220 | no matter what was going on in your life,

00:12:41.700 | about five to 10 minutes before those mealtimes,

00:12:44.980 | you would start to feel hungry and even a little agitated,

00:12:47.900 | which is your body's way of trying to get you

00:12:50.380 | to forage for food.

00:12:52.020 | And that's because of some peptide signals

00:12:54.580 | that come from the periphery from your body,

00:12:57.180 | things like hypocretinorexin,

00:13:00.060 | that signal to the hypothalamus and brainstem

00:13:02.660 | to make you active and alert and look for food

00:13:05.020 | and feel hungry.

00:13:06.400 | So there's kind of an anticipatory circuit

00:13:08.980 | that's a chemical circuit, but eventually over time,

00:13:11.920 | the neurons, the neural circuits

00:13:14.180 | that control hypocretinorexin would get tuned

00:13:16.820 | to the neural circuits that are involved in eating

00:13:20.380 | and maybe even smell and taste

00:13:22.960 | to create a kind of eating circuit

00:13:24.860 | that's unique to your pattern, to your rhythms.

00:13:28.340 | The same thing is true for these waking and exercise

00:13:32.020 | and other schedules, including ultradian schedules.

00:13:34.700 | If you wake up in the morning

00:13:36.660 | and start getting your sunlight,

00:13:37.820 | you start exercising in the morning

00:13:40.100 | or you exercise in the afternoon,

00:13:42.100 | pretty soon your body will start to anticipate that

00:13:44.260 | and start to secrete hormones and other signals

00:13:46.940 | that prepare your body for the ensuing activity

00:13:50.260 | of waking up or going to sleep.

00:13:52.280 | So if you get onto a pattern or a rhythm,

00:13:55.960 | even if that rhythm isn't down to the minute,

00:13:58.800 | you'll find that there's plasticity in these circuits

00:14:01.080 | and it becomes easier to wake up early if that's your thing

00:14:03.740 | or exercise at a particular day if that's your thing.

00:14:07.100 | That's the beauty of neural plasticity.

00:14:10.120 | A number of people asked,

00:14:11.160 | "What can I do to increase plasticity?"

00:14:13.920 | And that really comes in two forms.

00:14:16.200 | There's plasticity that we can access in sleep

00:14:19.860 | to improve rates of learning and depth of learning

00:14:24.080 | from the previous day or so.

00:14:25.980 | And there's this NSDR, non-sleep deep rest,

00:14:29.280 | that can be done without sleeping

00:14:30.960 | to improve rates of learning and depth of retention, et cetera.

00:14:34.460 | So let's consider those both

00:14:36.680 | and you can incorporate these protocols if you like.

00:14:38.760 | Again, these are based on quality peer-reviewed studies.

00:14:42.580 | First, let's talk about learning in sleep.

00:14:45.200 | This is based on some work

00:14:46.340 | that I'll provide the reference for

00:14:48.840 | that was published in the journal "Science."

00:14:51.620 | Excellent journal.

00:14:52.500 | Matt Walker also talks about some of these studies

00:14:55.300 | done by others in his book, "Why We Sleep."

00:14:58.820 | The studies, just to remind you,

00:15:00.580 | are structured the following way.

00:15:02.660 | An individual is brought into a laboratory,

00:15:06.220 | does a spatial memory task.

00:15:07.860 | So there tends to be a screen

00:15:10.780 | with a bunch of different objects

00:15:12.560 | popping up on the screen in different locations.

00:15:14.380 | So it might be a bulldog's face,

00:15:15.980 | there might be a cat, then it might be an apple,

00:15:18.000 | then it might be a pen in different locations.

00:15:20.180 | And that sounds trivially easy,

00:15:21.940 | but with time, you can imagine it gets pretty tough

00:15:24.600 | to come back a day later and remember

00:15:26.620 | if something presented in a given location

00:15:29.060 | was something you've seen before

00:15:30.500 | and whether or not it was presented in that location

00:15:32.300 | or a different location.

00:15:33.300 | If you had enough objects and changed the locations enough,

00:15:36.020 | this can actually be quite difficult.

00:15:38.140 | In this study, the subjects

00:15:40.420 | either just went through the experiment

00:15:43.260 | or a particular odor was released into the room

00:15:47.820 | while they were learning

00:15:49.500 | or a tone was played in the room while they were learning.

00:15:52.980 | And then during the sleep of those subjects

00:15:56.780 | the following night and the following night,

00:15:59.540 | this was done repeatedly for several nights,

00:16:03.220 | the same odor or tone was played

00:16:06.860 | while the subjects were sleeping.

00:16:08.820 | They did this in different stages of sleep,

00:16:11.420 | non-REM sleep and rapid eye movement sleep, REM sleep.

00:16:14.660 | They did this with just the tone in sleep.

00:16:18.460 | If the subjects had the odor, but not the tone,

00:16:21.940 | they did it with putting the tone.

00:16:24.420 | If they had the odor while learning,

00:16:26.200 | so basically all the controls,

00:16:27.420 | all the things you'd want to see done

00:16:29.000 | to make sure that it wasn't some indirect effect,

00:16:31.140 | some modulatory effect, okay?

00:16:33.400 | And what they found was that providing the same stimulus,

00:16:38.400 | the odor if they smelled an odor or a tone,

00:16:41.480 | if the subjects heard a tone while learning,

00:16:44.440 | if they just delivered that odor or tone

00:16:46.980 | while the subjects slept,

00:16:48.940 | rates of learning and retention of information

00:16:51.460 | was significantly greater.

00:16:54.140 | This is pretty cool.

00:16:55.060 | What this means that you can cue the subconscious brain,

00:16:58.300 | the asleep brain to learn particular things better

00:17:02.460 | and faster.

00:17:03.820 | So how might you implement this?

00:17:05.120 | Well, you could play with this if you want.

00:17:07.340 | I don't see any real challenge to this

00:17:08.980 | provided the odor is a safe one

00:17:11.820 | and it doesn't wake you up

00:17:12.980 | and the tone is a safe one and doesn't wake you up.

00:17:17.060 | You could do this by having a metronome, for instance,

00:17:20.060 | while learning something,

00:17:21.460 | playing in the background or particular music,

00:17:23.340 | and then have that very faintly while you sleep.

00:17:26.020 | So you could apply this if you like and try this.

00:17:28.820 | The other form of neuroplasticity

00:17:30.220 | is not the neuroplasticity that you're amplifying

00:17:33.380 | by listening to tones or smelling odors in sleep,

00:17:37.900 | but the neuroplasticity that you can access

00:17:39.580 | with non-sleep deep rest.

00:17:41.620 | So NSDR, non-sleep deep rest,

00:17:44.640 | as well as short 20-minute naps,

00:17:46.820 | which are very close to non-sleep deep rest

00:17:48.980 | because people rarely drop into deep states of sleep

00:17:51.660 | during short naps unless they're very sleep deprived.

00:17:54.480 | NSDR has been shown to increase rates of learning

00:18:00.340 | when done for 20-minute bouts

00:18:02.420 | to match an approximately 90-minute bout of learning.

00:18:07.860 | So what am I talking about?

00:18:09.140 | 90-minute cycles are these ultradian cycles

00:18:12.220 | that I've talked about previously.

00:18:13.840 | And we tend to learn very well

00:18:16.060 | by taking a 90-minute cycle,

00:18:17.960 | transitioning into some focus mode early in the cycle

00:18:20.940 | when it's hard to focus,

00:18:21.780 | and then deep focus and learning

00:18:24.620 | feels almost like agitation and strain.

00:18:26.760 | And then by the end of that 90-minute cycle,

00:18:29.060 | it becomes very hard to maintain focus

00:18:32.160 | and learn more information.

00:18:34.140 | There's a study published in Cell Reports last year,

00:18:36.460 | a great journal, excellent paper,

00:18:39.340 | showing that 20-minute naps

00:18:41.740 | or light sleep of the sort of non-sleep deep rest

00:18:45.460 | taken immediately after, or close to,

00:18:48.540 | it doesn't have to be immediately

00:18:49.660 | after you finish the last sentence of learning

00:18:51.580 | or whatever it is, or bar of music,

00:18:54.540 | but a couple minutes after transitioning

00:18:56.660 | to a period of non-sleep deep rest

00:18:59.380 | where you're turning off the analysis

00:19:01.420 | of duration, path, and outcome

00:19:02.660 | has been shown to accelerate learning

00:19:04.860 | to a significant degree,

00:19:06.460 | both the amount of information

00:19:08.180 | and the retention of that information.

00:19:10.140 | So that's pretty cool

00:19:11.720 | because this is a cost-free, drug-free way

00:19:16.500 | of accelerating learning without having to get more sleep,

00:19:20.000 | but simply by introducing these 20-minute bouts.

00:19:23.100 | I would encourage people, if they want to try this,

00:19:25.140 | to consider the 20 minutes per every 90 minutes

00:19:28.680 | of Ultradian learning cycle,

00:19:30.320 | which brings us to the next thing

00:19:31.860 | about learning and plasticity,

00:19:33.700 | which is nootropics, aka smart drugs.

00:19:36.780 | Ah, this is a big topic.

00:19:39.860 | That sigh was a sigh of concern

00:19:42.860 | about how to address nootropics

00:19:44.820 | in a thorough enough, but thoughtful enough way.

00:19:48.340 | There are elements to learning

00:19:49.740 | that we've discussed here before that are very concrete.

00:19:52.980 | Things like the ability to focus

00:19:55.380 | and put the blinders on to everything else

00:19:57.420 | that's happening around you and in your head mainly, right?

00:20:01.300 | Distractions about things you should be doing,

00:20:03.040 | could be doing, or might be doing,

00:20:04.900 | and focus on what you need to do.

00:20:07.060 | And then that's required

00:20:08.540 | for triggering the acetylcholine neuromodulator

00:20:11.460 | that will then allow you to highlight

00:20:14.380 | the particular synapses

00:20:15.380 | that will then later change in sleep.

00:20:17.460 | So no nootropic allows you to bypass the need

00:20:20.460 | for sleep and deep rest.

00:20:22.480 | That's important to understand.

00:20:23.900 | Right now, most nootropics tend to bundle

00:20:26.180 | a bunch of things together.

00:20:27.360 | Most of them include some form of stimulant, caffeine.

00:20:30.740 | You can't just ingest more stimulant to be more focused.

00:20:34.120 | It doesn't work that way.

00:20:35.080 | Most nootropics also include things that increase

00:20:38.560 | or are designed to increase acetylcholine.

00:20:40.960 | Things like alpha-GPC and other things of that sort.

00:20:44.620 | And indeed, there's some evidence

00:20:46.360 | that they can increase acetylcholine.

00:20:48.240 | So we need the focus component.

00:20:50.040 | We need the alertness component.

00:20:51.280 | The alertness component comes from epinephrine,

00:20:53.120 | traditionally from caffeine stimulation.

00:20:55.560 | The acetylcholine stimulation traditionally comes

00:20:58.400 | from choline donors or alpha-GPC, things of that sort.

00:21:02.120 | And then you would want to have some sort of off switch

00:21:05.320 | because anything that's going to really stimulate

00:21:08.200 | your alertness that then provides a crash,

00:21:10.680 | that crash is not a crash into the deep kind

00:21:13.200 | of restful slumber that you would want for learning.

00:21:16.840 | It's a crash into the kind of,

00:21:18.820 | let's just call it lopsided sleep,

00:21:23.120 | meaning it's deep sleep, but it lacks certain spindles

00:21:26.840 | and other elements of the physiology sleep spindles

00:21:29.480 | that really engage the learning process

00:21:32.000 | and the reconfiguration of synapses.

00:21:34.200 | So right now, my stance on nootropics is that maybe,

00:21:39.200 | maybe for occasional use, provided it's safe for you,

00:21:43.880 | I'm not recommending it, but in general,

00:21:46.800 | it tends to use more of a shotgun approach

00:21:49.880 | than is probably going to be useful for learning

00:21:53.080 | and memory in the long run.

00:21:55.040 | Okay, I'd like to continue by talking about the role

00:21:57.480 | of temperature in sleep, accessing sleep,

00:22:01.640 | staying asleep and wakefulness.

00:22:04.360 | Temperature is super interesting as it relates

00:22:06.800 | to circadian rhythms and wakefulness and sleep.

00:22:10.240 | First, let's take a look at what's happening

00:22:12.200 | to our body temperature across each 24 hour cycle.

00:22:17.200 | In general, our temperature tends to be lowest

00:22:20.400 | right around 4 a.m. and starts creeping up around 6 a.m.,

00:22:25.280 | 8 a.m. and peaks sometime between 4 p.m. and 6 p.m.

00:22:30.280 | There's also an important way in which temperature

00:22:32.960 | matches day length.

00:22:33.960 | In general, as days get longer, it tends to be hotter out.

00:22:38.000 | Not always, but in general, that's the way it is.

00:22:40.720 | And as days get shorter, it tends to be colder outside.

00:22:44.160 | So temperature and day length are also linked.

00:22:47.880 | Metabolically, they're linked.

00:22:49.280 | Biologically, they're linked, excuse me.

00:22:52.200 | And atmospherically, they're linked

00:22:53.760 | for the reasons that we talked about before

00:22:55.120 | about duration of day length

00:22:57.400 | and other climate features and so forth.

00:22:59.880 | So one of the most powerful things

00:23:01.920 | about setting your circadian rhythm properly

00:23:04.200 | is that your temperature will start to fall

00:23:06.640 | into a regular rhythm.

00:23:07.840 | And that temperature has a very strong effect

00:23:10.860 | on things like metabolism and when you will feel

00:23:14.720 | most willing and interested in exercising.

00:23:17.840 | Typically, the willingness to exercise and engage

00:23:20.600 | in any kind of activity, mental or physical,

00:23:22.680 | is going to be when that rise in temperature is steepest,

00:23:26.040 | when the slope of that line is greatest.

00:23:27.640 | That's why 30 minutes after waking

00:23:29.480 | is one of those key windows,

00:23:30.760 | as well as three hours after waking,

00:23:32.480 | and then when temperature actually peaks,

00:23:34.800 | which is generally, generally, about 11 hours after waking.

00:23:39.800 | So this is why we say that temperature

00:23:43.000 | and circadian rhythm are linked,

00:23:44.840 | but they're actually even more linked than that.

00:23:47.760 | We've talked before about how light enters the eye,

00:23:50.320 | triggers activation of these melanopsin cells,

00:23:52.560 | which then triggers activation

00:23:53.840 | of the suprachiasmatic nucleus,

00:23:55.360 | the master circadian clock.

00:23:57.120 | And then I always say the master circadian clock

00:23:59.080 | informs all the cells and tissues of your body

00:24:01.280 | and puts them into a nice cohesive rhythm.

00:24:04.200 | But what I've never answered

00:24:06.520 | was how it actually puts them into that rhythm.

00:24:09.120 | And it does it two ways.

00:24:10.800 | One is it secretes a peptide.

00:24:12.600 | A peptide is just a little protein

00:24:13.920 | that floats through the bloodstream

00:24:15.840 | and signals to the cells.

00:24:17.080 | But the other way is it synchronizes the temperature

00:24:19.960 | under which those cells exist.

00:24:22.100 | So temperature is actually the effector

00:24:24.440 | of the circadian rhythm.

00:24:26.080 | Nowadays, there's some interest in cold showers

00:24:29.320 | and ice baths.

00:24:30.440 | Getting into an ice bath is very interesting

00:24:32.740 | because you have a rebound increase in thermogenesis.

00:24:36.200 | Now you should know from the previous episode

00:24:38.380 | that as that temperature increases,

00:24:40.680 | it will shift your circadian rhythm

00:24:42.640 | and which direction it shifts your circadian rhythm

00:24:44.800 | will depend on whether or not

00:24:45.640 | you're doing it during the daytime or late in the day.

00:24:47.440 | If you do it after 8 p.m.,

00:24:49.560 | it's going to make your day longer, right?

00:24:52.380 | Because your body and your central clocks

00:24:55.980 | are used to temperature going up

00:24:58.600 | early in the day and throughout the day

00:25:00.240 | and peaking in the afternoon.

00:25:01.440 | If you then increase that further

00:25:03.760 | or you simply increase it over its baseline at 8 p.m.,

00:25:06.740 | after temperature was already falling,

00:25:08.880 | even if it's just by a half a degree or a couple degrees,

00:25:11.220 | or you do that with exercise,

00:25:12.440 | doesn't have to be with the ice bath,

00:25:14.020 | you are extending, you are shifting forward,

00:25:16.460 | you're phase delaying your clock,

00:25:18.940 | you're convincing your clock

00:25:20.580 | and therefore the rest of your body

00:25:21.980 | that the day is still going, right?

00:25:24.180 | You're giving it the perception,

00:25:25.620 | the cellular and physiological perception

00:25:28.500 | that the day is getting longer

00:25:29.620 | and you will want to naturally stay up later

00:25:32.220 | and wake up later.

00:25:33.820 | So for those of you that are having trouble getting up,

00:25:36.020 | and this is going to almost sound laughable,

00:25:37.540 | but a cold shower first thing in the morning

00:25:39.380 | will wake you up,

00:25:40.620 | but that's waking you up in the short term

00:25:43.220 | because of a different mechanism,

00:25:44.540 | which I'll talk about in a moment,

00:25:45.940 | but it also is shifting your clock,

00:25:47.620 | it's phase advancing your clock

00:25:50.180 | in a way that makes you more likely

00:25:52.420 | to get up earlier the next day.

00:25:54.540 | It's going to make you want to wake up

00:25:56.520 | about half hour to an hour earlier the next day

00:25:59.040 | than you normally would.

00:25:59.940 | Whereas if you do it while your temperature is falling,

00:26:02.820 | it will tend to delay and make your body perceive

00:26:05.220 | as if the day is getting longer.

00:26:07.120 | But temperature is, again,

00:26:09.300 | it's not just one tool to manipulate wake up time

00:26:13.300 | and circadian rhythm and metabolism.

00:26:15.480 | It is the effector.

00:26:16.780 | It is the way that the central circadian clock

00:26:18.900 | impacts all the cells and tissues of your body.

00:26:21.000 | Light is the trigger.

00:26:22.460 | The suprachiasmatic nucleus

00:26:23.980 | is the master circadian clock

00:26:25.460 | that mediates all these changes.

00:26:27.780 | Also influenced by non-photic influence

00:26:29.700 | like exercise and feeding and things of that sort.

00:26:33.100 | But temperature is the effector.

00:26:34.780 | Now, you can also shift your circadian rhythm with eating.

00:26:39.180 | When you travel and you land in a new location

00:26:42.240 | and your schedule is inverted 12 hours,

00:26:45.220 | one way that we know you can shift your rhythm more quickly

00:26:48.060 | is to get onto the local meal schedule.

00:26:50.340 | Now that probably has to do with two effects.

00:26:51.900 | One are changes in temperature

00:26:53.180 | and eating-induced increases in body temperature.

00:26:55.740 | Now you should understand why that would work.

00:26:57.580 | As well as eating has this anticipatory secretion

00:27:01.400 | of hypercretinorexin that I talked about earlier.

00:27:04.260 | Many people asked questions about food and neurotransmitters

00:27:08.420 | and how those relate to sleep, wakefulness and mood,

00:27:11.520 | which is essentially 25 hours of content for me to cover.

00:27:16.520 | But I'm going to try and distill out

00:27:17.920 | the most common questions.

00:27:19.280 | We've talked a lot about neuromodulators

00:27:21.960 | like dopamine, acetylcholine and norepinephrine.

00:27:24.900 | You may notice in those discussions

00:27:27.340 | that the precursors to say serotonin is tryptophan.

00:27:31.060 | Tryptophan actually comes from the diet.

00:27:32.780 | It comes from the foods that we eat.

00:27:35.460 | Tyrosine is the precursor to dopamine.

00:27:38.860 | It comes from the foods that we eat.

00:27:41.020 | And then once we ingest them,

00:27:43.340 | those compounds circulate to a variety

00:27:46.940 | of different cells and tissues.

00:27:48.900 | But it is true that our food and the particular foods we eat

00:27:52.500 | can influence things like neuromodulator levels

00:27:55.940 | to some extent.

00:27:57.260 | Nuts and meats, in particular red meats,

00:27:59.580 | tend to be rich in things like tyrosine, right?

00:28:02.900 | That tells you right there

00:28:04.180 | that because tyrosine is the precursor of dopamine

00:28:06.500 | and dopamine is the precursor of norepinephrine

00:28:09.100 | and epinephrine,

00:28:10.500 | that those foods tend to lend themselves

00:28:13.900 | toward the production of dopamine and epinephrine

00:28:18.080 | and the sorts of things

00:28:19.340 | that are associated with wakefulness.

00:28:21.980 | Now, of course, the volume of food that we eat

00:28:24.500 | also impacts our wakefulness.

00:28:25.860 | If we eat a lot of anything,

00:28:27.700 | whether or not it's ribeye steaks, rice or cardboard,

00:28:31.760 | please don't eat cardboard,

00:28:33.020 | your stomach, if it's very distended,

00:28:35.140 | will draw a lot of blood into your gut

00:28:37.460 | and you will divert blood from other tissues

00:28:39.920 | and you'll become sleepy.

00:28:41.000 | So it's not just about food content,

00:28:42.540 | it's also about food volume, all right?

00:28:44.920 | Fasting states generally are associated

00:28:48.040 | with more alertness, epinephrine and so forth.

00:28:50.980 | And fed states are generally associated

00:28:54.540 | with more quiescence and relaxation, serotonin

00:28:57.900 | and the kind of things that lend themselves

00:28:59.900 | more towards sleep and less toward alertness.

00:29:02.940 | And fed states are generally associated

00:29:06.480 | with more quiescence and relaxation,

00:29:08.660 | serotonin and the kind of things

00:29:11.200 | that lend themselves more towards sleep

00:29:13.520 | and less toward alertness.

00:29:15.460 | There are a couple effects of food that are independent,

00:29:19.560 | or I should say a couple effects of eating,

00:29:21.180 | 'cause the food won't do it

00:29:22.120 | when it's sitting across the table,

00:29:23.280 | but of eating that are powerful

00:29:26.900 | for modulating circadian rhythm, wakefulness, et cetera.

00:29:30.060 | And that's because every time we eat,

00:29:31.380 | we get eating-induced thermogenesis

00:29:33.940 | regardless of what we eat.

00:29:35.260 | And now you know from the discussion about temperature

00:29:37.220 | that if you're eating early in the day,

00:29:39.100 | you're tending to shift your rhythm earlier

00:29:41.100 | so that you'll want to wake up earlier the next day.

00:29:44.500 | If you're eating very late in the day,

00:29:46.380 | even if you can fall asleep after that,

00:29:48.660 | there's a tendency for you

00:29:49.620 | to want to sleep later the next day.

00:29:51.660 | So as we finish up,

00:29:53.100 | I just want to offer you the opportunity

00:29:55.480 | to do an experiment.

00:29:56.780 | It might be interesting, just a suggestion,

00:29:59.500 | to write down for each day

00:30:02.900 | when you went outside to get sunlight

00:30:05.640 | and when you did that relative to wakings.

00:30:07.900 | And then you might just take note of when you exercised,

00:30:11.960 | and you might note

00:30:13.460 | when you might've felt chilled or cold if you do,

00:30:16.300 | or you might've felt particularly hot,

00:30:18.320 | or if you woke up in the middle of night

00:30:19.480 | when you felt particularly hot.

00:30:20.500 | And then the last thing you might want to do

00:30:22.240 | is just write down

00:30:23.540 | if and when you did a non-sleep-deep-rest protocol,

00:30:26.260 | an SDR protocol,

00:30:27.440 | anything that you're using

00:30:30.340 | to deliberately teach your nervous system

00:30:33.220 | how to go from more alertness to more calmness

00:30:35.680 | in the waking state.

00:30:36.980 | By doing this,

00:30:37.820 | you can start to reveal some really interesting patterns.

00:30:40.260 | It's really about taking the patterns of behaviors,

00:30:43.420 | of waking and light viewing and eating and exercise,

00:30:46.780 | and superimposing that

00:30:49.340 | on what you're learning in this podcast

00:30:51.580 | and elsewhere, of course,

00:30:52.960 | and what you already know,

00:30:54.180 | and trying to see where certain problems

00:30:57.560 | or pain points might be arising.

00:30:58.940 | Maybe you start to find that using cold exposure

00:31:02.380 | early in the day is great for you,

00:31:04.060 | but using it late,

00:31:05.220 | if it's too late in the day, that's not great.

00:31:07.060 | Or if you're into the sauna,

00:31:09.580 | or even like some people, including myself,

00:31:11.940 | if I take a hot shower

00:31:13.020 | or sit in a hot tub or a sauna late at night,

00:31:15.560 | well, then I get a compensatory decrease in body temperature

00:31:18.820 | and I sleep great,

00:31:19.860 | provided I hydrate well enough,

00:31:21.420 | 'cause that can be kind of a dehydrating thing

00:31:23.140 | to sit in hot conditions.

00:31:25.420 | But if I do the sauna early in the day,

00:31:27.800 | unless I exercise immediately afterward,

00:31:30.900 | then I tend to get the temperature drop,

00:31:32.780 | which makes sense because we can get in the sauna,

00:31:34.620 | you get vasodilation, you throw off a lot of heat,

00:31:37.580 | and then you generally get

00:31:38.420 | a compensatory drop in temperature.

00:31:39.840 | If you do that early in the day,

00:31:40.860 | that's right about the time that that temperature

00:31:43.420 | is trying to entrain the circadian clocks of your body.

00:31:45.800 | So I just encourage you to start becoming scientists

00:31:49.100 | of your own physiology, of your own brain and body,

00:31:52.660 | and seeing how the various tools

00:31:53.980 | that you may or may not be using

00:31:55.980 | are affecting your patterns of sleep,

00:31:58.740 | your patterns of attention and wakefulness.

00:32:01.060 | It's vitally important that if you do this,

00:32:03.700 | that you know that it's not about trying to get onto

00:32:07.100 | an extremely rigid schedule.

00:32:09.120 | It's really about trying to identify variables

00:32:11.660 | that are most powerful for you

00:32:13.660 | and that push you in the direction that you want to go,

00:32:15.900 | and changing the variables that are pushing your body

00:32:19.060 | and your mind in the directions that you don't want to go.

00:32:21.240 | Self-experimentation is something

00:32:22.980 | that should be done slowly, carefully.

00:32:25.560 | You don't want to be reckless about this.

00:32:27.360 | And this is where I would say

00:32:29.920 | manipulating one or two variables at a time

00:32:32.200 | is really going to be best,

00:32:33.200 | as opposed to changing a dozen things all at once

00:32:35.980 | to really identify what it is that's most powerful for you.

00:32:39.480 | And above all, thank you for your interest in science.

00:32:42.240 | [upbeat music]

00:32:44.820 | (upbeat music)

Essentials: Using Science to Optimize Sleep, Learning & Metabolism

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