Welcome to the Huberman Lab Podcast, where we discuss science and science-based tools for everyday life. I’m Andrew Huberman, a professor of neurobiology and ophthalmology at Stanford School of Medicine. Today’s podcast episode is all about sleep and the mirror image of sleep, which is wakefulness. These two phases of our life govern everything about our mental and physical health. We’re not just gonna talk about what’s useful about sleep, we’re also gonna talk about how to get better at sleeping, including how to get better at falling asleep, timing your sleep, and accessing better sleep quality. In doing so, we’re also gonna discuss how to get more focused and alert in wakefulness.

Today’s podcast is brought to us by Helix mattresses. Having the proper sleep environment, both the environment you’re sleeping in and the object you’re sleeping on, is critically important to getting a good night’s sleep. Helix mattresses are a little different than most because they’re matched to your specific sleep needs, as well as whether or not you tend to run hot or cold as you sleep through the night, what position you sleep in, and so forth. If you go to their website, they have a quiz that you can take that matches you to the particular mattress that’s gonna be best for your sleep needs.

As always, I wanna just mention that this podcast is part of my effort to bring zero-cost-to-consumer public education about science and science-related tools, it is unrelated to my teaching and research roles at Stanford School of Medicine. You may catch a few snores in the background. Unlike me, my bulldog, Costello, can fall asleep anywhere, anytime, and he happens to be sleeping over there in the corner, so if you hear snoring, that’s what that’s about.

I’ve always had trouble sleeping. I’m one of those people who can fall asleep easily, but then I wake up and have a hard time getting back to sleep. I recently switched to a Helix mattress, which is precisely matched to my sleep needs, and it has made a tremendous difference. If you’re interested in trying a Helix mattress, go to helixsleep.com/huberman to get up to $200 off your order and two free pillows.

Mindfulness meditation is also important for good sleep. There is a lot of research out there that supports the fact that mindfulness meditation can support mental and physical health. However, many people find it hard to meditate, myself included. I started meditating in my teens but would drop it every few weeks or so. Then, a few years ago, I was flying a lot for work and I discovered Headspace, a meditation app that teaches how to meditate. As I started meditating more regularly, I found that my sleep was better and I would arrive feeling more rested. If you want to try Headspace, go to headspace.com/specialoffer and get one month of all of Headspace’s meditations for free.

Sleep is an incredible period of our lives where we are not conscious, but it is still very important because it resets our ability to be focused, alert, and emotionally stable in the wakeful period. This is why it is important to think about both sleep and wakefulness when discussing focus, motivation, mood, wellbeing, and other aspects of life.

The second force that governs our sleep and wakefulness is a bit more mysterious, it’s called the circadian rhythm. The circadian rhythm is basically the internal clock that our bodies use to tell time and to tell when we should be awake and when we should be asleep. It’s a 24-hour cycle that is regulated by light and darkness, and it’s influenced by other factors, like temperature and our social environment, and it’s really important for us to understand the relationship between the circadian rhythm and the adenosine cycle in order to have the best possible sleep.

The reason you get sleepy when you’ve been up for a while is because adenosine is creeping up steadily. A good way to remember this is to think about caffeine. For most people, caffeine wakes them up and makes them feel more alert. However, some people are so sensitive to caffeine that they feel jittery even in small amounts, while others can drink large amounts without feeling jittery. Caffeine acts as an adenosine antagonist, meaning when ingested, it binds to the adenosine receptor and blocks the sleepiness signal. When the caffeine wears off, adenosine binds to the receptor, which can cause a crash and make you feel especially tired.

Caffeine has health benefits, but it can also be problematic for some people. It can raise blood pressure and increases dopamine, a neuromodulator that makes us feel good, motivated, and gives us energy. Everyone needs to figure out what’s right for them in terms of caffeine tolerance and the times of day they can have it in order to get good sleep. Experimenting is the best way to determine this.

Caffeine has tremendous variation in its effects on individuals. Currently, the only way to decide whether or not caffeine is good or bad for you and when to ingest it is to experiment and figure out what works for you. Adenosine drives the sleep hunger – when adenosine is low, we’re not very hungry and when it’s high, we want to fall asleep. If you stay up for four hours more than usual, you’ll be very sleepy because adenosine is building up. However, if you pull an all-nighter, you’ll feel an increase in energy and alertness as morning rolls around. This is because there is a second force governing when you sleep and wake, called a circadian force. This force is governed by light, in particular sunlight, and is actionable. Finally, people tend to make a mess of this literature, so it’s important to understand what’s going on in your brain and body as you go through one 24-hour day.

Waking up is an important part of the day. Regardless of how well you slept at night, most people tend to wake up sometime around when the sun rises, maybe not right at sunrise, but within an hour or two or maybe three of sunrise. There are exceptions, such as night-shift workers and people experiencing jet lag, which will be discussed at the end of the podcast. When we wake up, adenosine levels tend to be low and our system generates an internal signal in the form of a hormone. This hormone is cortisol and it is released from our adrenal glands, which are located above our kidneys. This pulse of cortisol, as well as adrenaline and epinephrine, can come from our alarm clocks or from naturally waking up. It alerts our body to increase our heart rate, tense our muscles, and start moving about. Cortisol is also associated with stress, as different events throughout the day can cause us to feel more alert and release cortisol pulses. It is important that this cortisol pulse occur early in the day and that it happens all at once, as it sets a rising tide of cortisol in our system. This cortisol is healthy and wakes us up, making us feel alert and wanting to move and go about our day.

When you wake up in the morning, your body experiences a rise in cortisol, which sets a timer in your body and nervous system. This timer dictates when melatonin, which makes you sleepy, will be secreted from the pineal gland, a pea-sized organ located near the fourth ventricle. Melatonin is the only hormone released from the pineal, and is known to suppress the onset of puberty. While supplements may be available, it is important to consult a healthcare professional before adding anything to your routine.

Melatonin is known to suppress the onset of puberty, so much so that regular, cyclic periods of melatonin release from the pineal really correlate with the onset of puberty and early adulthood. This means that as we start secreting melatonin only at night, that’s also when we tend to transition out of puberty. While this correlation does not necessarily mean that melatonin controls the onset of puberty, there is a lot of data, endocrinology and other evidence that suggests it does. For this reason, supplementing melatonin could be problematic for those who have not yet gone through puberty. However, for those who have already gone through puberty, it may have some impact on other hormone systems in the body, which is why I personally don’t like to use melatonin to fall asleep.

Additionally, melatonin will help you fall asleep but not stay asleep. Many people who take melatonin find that they wake up three to five hours later unable to fall back asleep. This could be due to the fact that melatonin is available over the counter in most areas of the world, even though it is a hormone, and the amount of melatonin in commercially available melatonin can range anywhere from 15% of what is listed on the bottle to 400 times more than what is listed on the bottle. This means that taking melatonin is completely unregulated.

The rhythm of cortisol and melatonin is endogenous, meaning it happens in us all the time without any external input. However, external things can govern when these rhythms happen. This is related to the episode one of the podcast, where we discussed sensation and perception. When we wake up and open our eyes, light comes into our eyes, triggering the rise of cortisol. Under normal circumstances, this happens once per 24-hour cycle, but in complete darkness it would happen later and later each day.

The way this system works is that you have a particular set of neurons in your eye called retinal ganglion cells. These retinal ganglion cells are brain neurons and reside outside of the skull. When light comes into the eye, an electrical signal is sent to a central clock we call the suprachiasmatic nucleus, which has connections with essentially every cell and organ of the body. It is vitally important that we get light communicated to this central clock in order to time the cortisol and melatonin properly, as not doing so can have tremendously broad and bad effects on various aspects of health.

It turns out that these neurons in our eye respond best to a particular quality and amount of light that comes from sunlight. These neurons don’t know anything about sunrises or sunsets, they only know the quality of light that comes in when the sun is low in the sky. When the sun is low in the sky, there is a particular contrast between yellows and blues that triggers the activation of these cells.

Therefore, if you wake up and look at your phone or computer, or flip on a bunch of artificial lights, these cells will be activated, but not in the optimal way. What you want to do is get sunlight in your eyes as close to waking as possible. You don’t need the sunlight beaming you directly in the eyes, but rather the light energy scattered from sunlight at this time.

Paragraph 1: Now, I know many of you are already asking, “Well, I live in Scandinavia,” or, “I can’t get sunlight, there’s buildings around me,” et cetera, we will get to all of that, but it’s critically important that you get outside to get this light. I had a discussion with a colleague of mine, Dr. Jamie Zeitzer, who’s in the Department of Psychiatry and Behavioral Sciences at Stanford, a world expert in this, and he tells me that it’s 50 times less effective to view this sunlight through a window, through a car windshield, or through the side window of a car than it is to just get outside with no sunglasses and view light early in the day.

Paragraph 2: Now, if you can’t see the sunrise, like I said, you can see this within an hour or two of sunrise, but it has to be low solar angle, once the sun is overhead, the quality of light shifts so that you miss this opportunity to time the cortisol pulse, and that turns out to be a bad thing to do, you really wanna time that cortisol pulse properly because, we’ll get into this a little bit more later, but a late-shifted cortisol pulse, in particular, a 9:00 p.m. or 8:00 p.m. increase in cortisol is one of the consequences, and maybe one of the causes, of a lot of anxiety disorders and depression, so it’s kind of a chicken-egg thing, we don’t know whether or not it’s correlated with, it’s the cause, or the effect, but it’s a signature of depression and anxiety disorder.

Paragraph 3: Bringing that cortisol pulse earlier in your wakeful period, earlier in your day, has positive benefits ranging from blood pressure to mental health, et cetera, not gonna list them all off because there’s just so many of them, but many, many positive things happen when you are getting the cortisol early in the day far away from your melatonin pulse. Okay, so how long should you be outside? Well, this is gonna vary tremendously because some people live in environments where it’s very bright, so let’s say it’s Colorado in the middle of winter, there’s a snowfield, there’s no cloud cover, and you walk outside, there’s going to be so much photon light energy arriving on your retina that it probably only takes 30 to 60 seconds to trigger the central clock and set your cortisol and melatonin rhythms properly and get everything lined up nicely, whereas if you’re in Scandinavia in the depths of winter and you wake up at 5:00 a.m. and the sun is just barely creeping across the horizon and then goes back down again a few hours later, you probably are not getting enough sunlight in order to set these rhythms, so many people find that they need to use sunlight simulators in the form of particular lights that were designed to simulate sunlight.

Paragraph 4: However, and I’m not out to attack the companies that produce those, there’s another solution to that, you can simply go outside for longer, even if there’s a lot of dense cloud cover, you’re probably getting anywhere from 10,000 to 50,000 lux, L-U-X, which is just a measure of light energy, and that should be sufficient to set the circadian clock. You could say, “Well, the lights in my house or my phone are really, really bright, right? Everyone’s telling us to stay off our phones at night because they’re really bright,” but guess what, it turns out that early in the day, your retina is not very sensitive, which means you need a lot of photons, ideally coming from sunlight, to set these clock mechanisms, so looking at your phone or artificial lights is fine if you wake up before sunrise, but it’s not going to work to set these clock mechanisms, and this is supported by dozens, if not hundreds, of quality peer-reviewed studies, so you wanna use sunlight, if you can’t see sunlight because of your environment, then you are going to have to opt for artificial light, and in that case, you’re going to want an artificial light that either simulates sunlight or has a lot of blue light.

Paragraph 5: Now, without going off course here, you might be saying, “Wait, I’ve heard blue light is bad for me.” Actually, blue light is great for this mechanism during the day, we can talk about blue light and blue blockers, but you really want a lot of blue and yellow light arriving on the retina early in the day. Let me be clear about something, you never ever want to look at any light, sunlight or artificial light, that is painful to look at.

If you find that your eyes are watering or you’re having challenges maintaining, looking at this thing for a while because it’s painful, that light is too bright and you do not wanna damage your retina, so you don’t wanna gaze at the sun refusing to blink and burn your retina, that’s actually possible to do. You have a proper blink reflex installed in you since birth, and if you feel like something’s too bright and you need to blink, it means you need to blink; that it’s too much light, so please don’t beam your eyes with really bright light.

But blue light, in particular, blue light and yellow light coming from sunlight is ideal. If you’re going to get it from artificial light because you can’t get enough sunlight, well then, artificial lights that are rich in blue, blue wavelengths, are going to be ideal for setting this mechanism. A lot of people will say, “Oh, I should be wearing blue blockers throughout the day.” No, that’s the exact wrong thing; if you’re going to use blue blockers, we can talk about that, that should be reserved for late in the evening because light suppresses melatonin.

I’ve been asked many times before about this pineal gland and there are a lot of ancient practices that map to some of the things that I’m saying, and people will always say, “Oh, I heard that sunlight is great for the pineal.” Well, perhaps, but we have to careful about that phrase; sunlight inhibits the pineal, it prevents it from releasing melatonin, darkness allows the pineal to release melatonin. So the pineal is not the gland or the organ of sunlight, it is the gland of darkness. In fact, melatonin can be thought of as a sleepiness signal that’s correlated with darkness.

So get up each morning, try and get outside. I know that can be challenging for people, but anywhere from 2 to 10 minutes of sunlight exposure is going to work well for most people, and you wanna do this on a regular basis and you don’t have to do it exactly at sunrise. I realize I’m repeating myself, but somehow, despite barking at people about this for a couple years now, I keep getting the same questions, and somehow, it hasn’t been sinking in, which could be related to some circadian disorder, I’m just kidding, if it’s not sinking in, it’s probably that I’m not being effective in communicating the information.

But get that bright light early in the day from sunlight, and if you can’t get it from sunlight, get it from artificial light. What kinds of artificial lights will work? Well, there are these sunrise simulators, but the ring lights that people use for selfies and this sort of thing, for posting on Instagram, those generate a lot of blue light. If wanna get experimental about this, there’s a free app, I have no relationship to the app, but it’s a great app called Light Meter that you can use your phone and you can measure the amount of photon energy in your environment, and it’s kind of a fun experiment to do.

You can go outside in the morning and you’ll see that there’s 10,000, 20,000 lux, even though it might seem like it’s kinda dim or there’s tree cover or cloud cover, you go inside and you shine an artificial light at your phone, press the button on Light Meter and you’ll find that it’s only 500 or 1,000 lux, and you realize that even though it seems really bright, the artificial light is very condensed, whereas the outside light is scattered in the atmosphere, and so you can think that you’re not getting much sunlight but you’re actually getting much more outside.

So get outside, get that sunlight early in the day, and try and do it on a consistent basis. If you can’t do it every day or you sleep through this period of the early day, low solar angle, don’t worry about it, these systems in the body, these hormone systems and neurotransmitter systems that make you awake at certain periods of the day and sleepy at other times are operating by averaging when you view the brightest light. Now, that can immediately tell us that what most people are doing is terrible, they’re waking up and they’re looking at their phone, which isn’t triggering activation of these cells in the eye and the central circadian clock.

Then a few hours later, they might get in their car with sunglasses and drive. Now, a note about sunglasses and prescription lenses, absolutely never, ever, ever compromise safety for the sorts of things I’m talking about, so if you need to wear sunglasses for safety reasons, wear them, absolutely, if you wear prescription lenses or contacts, wear them, they won’t filter out the wavelengths of light that are necessary for setting these central clocks, so safety first, of course. If you have a retinal degenerative disorder

Light viewed by our eyes,
particularly melanopsin ganglion cells, is the primary way to set our circadian rhythms. It dictates how well and when we will want to fall asleep later in the day. For those of us who are night owls, it may be that we are not getting enough sunlight early in the day. Other things, such as timing of food intake, exercise, and certain drugs or chemicals can help establish this rhythm of cortisol followed by melatonin 12-16 hours later.

The suprachiasmatic nucleus is the central clock which is governed by light, and the melanopsin ganglion cells are the only direct input to the clock. David Berson at Brown University is credited with the discovery of these cells. In addition to light, the intergeniculate leaflet, which sits a few millimeters away in the brain, is involved in regulating the clock output through non-light influences such as exercise and feeding.

By getting light exposure and exercising early in the day, we can naturally start to wake up earlier in the day. This is because these clock mechanisms have shifted, similar to setting the clock earlier as opposed to delaying the clock. All of these factors are important for establishing healthy sleep-wake rhythms and for allowing us to fall asleep easily at night.

Humans don’t have that, so the only way to get light information to your brain and to your body is through your eyes.
The main thing is that bright light early in the day, and the other thing is sunset, when the sun is also at a low solar angle, close to the horizon. By viewing sunlight at that time of day in the evening or afternoon, depending on what time of year it is and where you are in the world, these melanopsin cells, these neurons in your eye, signal the central circadian clock that it’s the end of the day.

A study published last year showed that viewing sunlight around the time of the sunset, doesn’t have to be just crossing the horizon, but circa sunset, within an hour or so of sunset, prevents some of the bad effects of light in preventing melatonin release later that same night. To do this, you’d go view the sunset or you would go outside in the late afternoon or evening, with sunglasses off if you can. If you need to wear sunglasses, it will take much longer to get the same effect. The best thing to do is just to get outside for a few minutes, anywhere from 2 to 10 minutes. Having those two signals arriving to your central clock that your body, your internal world, knows when it’s morning and knows when it’s evening, is tremendously powerful.

A study published in “Science” more than 10 years ago showed that light shone on the back of the knee could set these circadian rhythms, but it was later retracted due to experimental flaws. The study was repeated and it turns out there is no extraocular photo reception in humans. Whatever somebody tells you that light to the skin or light to the wherever is beneficial for your health, we can talk about that, but there’s no way that light information is setting your clocks. The only way to get light information to your brain and to your body is through your eyes.

Light information is important for setting our body’s internal clock and regulating our circadian rhythms. We know this from genetic studies, and it’s important to get enough light exposure early in the day, including blue light. However, too much light exposure late in the day can be detrimental, as it can trigger the activation of the clock, making it harder to fall asleep and disrupt our sleep pattern. To avoid this, we should try to avoid bright light exposure between 11:00 p.m. and 4:00 a.m., and instead use red light. Additionally, the location of light is important, as the cells in our eye that signal the central clock reside mostly in the bottom half of our retina, viewing our upper visual field.

The cells in the bottom half of the retina are designed to detect sunlight, which is overhead. To avoid improper activation of these neurons, it is better to place lights used in the evening low in the physical environment, such as on desktops or the floor, as opposed to overhead lights. Candlelight does not trigger activation of these cells, and dim lights low in the physical environment are the best option. If one wakes up in the middle of the night, blue blockers and dim screens should be used. Additionally, exposure to sunlight early in the day and around sunset can have positive effects. For shift workers, an entire discussion should be devoted to how they can protect themselves against the negative health effects of shift work. Adenosine, cortisol, and melatonin are all involved in determining wakefulness and when one should be asleep, and adjusting food intake, light exposure, and exercise to the daytime can help.

Some people like to stop eating around 6:00 or 8:00 p.m. for metabolic reasons or to maintain or lose weight, however, this is not supported by the literature. The literature suggests restricting feeding to a certain period of each 24-hour cycle, rather than eating around the clock. For more information on intermittent and circadian fasting, Satchin Panda’s book, “The Circadian Code,” is a great resource. Additionally, light exposure can be used to wake up earlier. Jamie Zeitzer and colleagues conducted a study showing that turning on the lights before waking up, even if the eyelids are closed, can increase total sleep time and shift the time at which one feels sleepy. This is because light can penetrate the eyelids and activate neurons which go to the central clock. This illustrates an important principle of how humans are built, which is that they have the capacity for phase advances and phase delays. If light exposure is too late in the evening or middle of the night, it will delay the clock and make it difficult to want to wake up early and go to bed early. On the other hand, if light exposure is early in the day, it will phase-advance the clock and make one want to wake up early. To ensure good sleep, it is important to provide consistent light anchors early in the day and in the evening, and avoid light at night. Naps of less than one ultradian cycle can also be beneficial.

For some of us, taking naps is great. I personally love taking naps, while some people wake up feeling groggy. This may be due to not sleeping as well as they should at night or not sleeping for as long as they should. Others feel great after a nap. It’s similar to nutrition in that there are many different approaches, and it depends on the individual’s lifestyle and genetics. Additionally, everyone needs some form of light information arriving in their system at regular intervals.

Yoga nidra and meditation are two practices that are immensely beneficial and involve listening to a script or consciously bringing your body and mind into a state of deep relaxation. This can be done for 10-60 minutes at a time. Meditation and yoga nidra can help people learn to relax and turn off thinking in order to fall asleep. Reveriehealth.com has a number of science-supported, clinically supported hypnosis scripts that can help with rewiring the brain and neuroplasticity. Devoting time each day to getting better at falling and staying asleep is a great practice to adopt.

The other thing about these practices such as meditation, yoga nidra, and hypnosis, is that people often ask me when they should do them. I always say that the best time is when you first wake up in the morning, provided you’ve gotten your sunlight already, or if you wake up in the middle of the night, or any time of day. It’s always good for you because it’s a training mechanism by which you can self-train your nervous system to go from a state of heightened alertness to heightened relaxation.

We all have experienced that we can stay up if we want to, though some people can do it more easily than others. However, it’s very hard to make ourselves fall asleep. This is due to an asymmetry in the autonomic nervous system, which governs alertness and calmness. We can force ourselves to stay awake more easily than we can force ourselves to fall asleep.

This is why I encourage people to look towards the body, sunlight, avoiding bright light if it’s late at night, and other mechanisms that involve the body to control the mind, rather than trying to wrestle the mind into a certain pattern of relaxation. This is what I refer to as non-sleep deep rest (NSDR). It can reset one’s ability to be awake after emerging from it, as well as make it easier to fall asleep at night.

NSDR has some research to support it, such as a study done out of a university in Denmark. It showed that meditation and yoga nidra-type meditation allows dopamine and other neuromodulators in an area of the brain called the striatum to reset itself. NSDR is powerful because it doesn’t require that you take much time out of your day, or ingest anything except air, and it can have many positive effects.

Now, let’s talk about compounds that we can and should take in order to control and access better sleep and better wakefulness. We’ve talked about things you can do or not do, nutrition, and the timing of nutrition. Almost everything you could take will affect your circadian timing and behavior. So it’s important to be mindful of what you’re taking and how it will affect you.

There are a couple things that are directly in line with the biology related to falling and staying asleep and directly in line with the biology of wakefulness. Stimulants, such as cocaine, amphetamine, and prescription stimulants like modafinil or armodafinil, are designed to create wakefulness by increasing epinephrine and dopamine. While these might be appropriate in a proper setting prescribed by a professional, they have many addictive and terrible effects. There are also some supplements and things that are safer and can be beneficial for falling and staying asleep.

Magnesium, particularly magnesium threonate, is associated with transporters in the body that bring more of it into cells and allow people to feel drowsiness and help them fall asleep. I personally take 3 or 400 milligrams of magnesium threonate about 30 to 60 minutes before sleep. Theanine, 100 to 200 milligrams, can help turn off the mind and fall asleep. It is also being introduced to energy drinks to take away the jitters associated with drinking too much caffeine. However, energy drinks can contain a lot of L-taurine, which can cause microvascular damage. Apigenin, 50 milligrams, can also augment or support the creation of sleepiness. Sleepwalkers should be careful about taking theanine and everyone should consult a board-certified M.D. or healthcare professional before taking anything.

Apigenin is a potent estrogen inhibitor, so women who want to maintain their estrogen levels should avoid it. Men should also take this into consideration as estrogen is important for libido and cognition. There are other legal compounds that can help with sleep, but it is important to research the safety margins of any compound. A great website to check out is examine.com, which has links to peer-reviewed studies and warnings related to any supplement.

For further exploration into sleep and wakefulness, the Huberman Lab podcast is a great resource. The podcast dives deep into topics for several episodes at a time, and the community is best supported by questions and involvement. To support the podcast, subscribers are encouraged to check out the sponsors discussed at the beginning.