Essentials: Master Your Sleep & Be More Alert When Awake

**Andrew Huberman** (0:00)
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.
I'm Andrew Huberman, and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine. Today's podcast episode is all about sleep. We're also going to talk about the mirror image of sleep, which is wakefulness. Now, these two phases of our life, sleep and wakefulness, govern everything about our mental and physical health. And we're not just going to talk about what's useful about sleep. We're also going to talk about how to get better at sleeping. And that will include how to get better at falling asleep, timing your sleep and accessing better sleep quality. In doing so, we're also going to discuss how to get more focused and alert in wakefulness. So if you're like most people, which includes me, you have some challenges with sleep, at least every third or fifth night or so, and maybe even more often. So we're really going to go tool heavy today and talk about tools that can help you fall asleep, sleep better and emerge from sleep feeling more rested. So what determines how well we sleep and the quality of our wakeful state? Turns out that's governed by two forces. The first force is a chemical force. It's called adenosine. Adenosine is a molecule in our nervous system and body that builds up the longer we are awake. So if you've just slept for eight or nine or 10 really deep restful hours, adenosine is going to be very low in your brain and body. If however you've been awake for 10, 15 or more hours, adenosine levels are going to be much higher. Adenosine creates a sort of sleep drive or a sleep hunger. And a good way to remember this and think about adenosine is to think about caffeine. Caffeine for most people wakes them up. It makes them feel more alert. Caffeine acts as an adenosine antagonist. What that means is that when you ingest caffeine, whether or not it's coffee or soda or tea or in any other form, it binds to the adenosine receptor. It sort of parks there just like a car would park in a given parking slot. And therefore, adenosine can't park in that slot. Now, when caffeine parks in the adenosine receptor slot, nothing really happens downstream of that receptor. The receptor can't engage the normal cellular functions of making that cell and you feel sleepy. So the reason caffeine wakes you up is because it blocks the sleepiness receptor. It blocks the sleepy signal. And this is why when that caffeine wears off, adenosine will bind to that receptor, sometimes with even greater, what we call affinity, and you feel the crash. You feel especially tired. Caffeine has a lot of health benefits. It also, for some people, can be problematic for health. It can raise blood pressure, et cetera. Caffeine increases this molecule that's a neuromodulator that we call dopamine. We discussed this in episode one, which tends to make us feel good, motivated, and give us energy. Because, as you may have learned in episode one, dopamine is related to another neuromodulator called epinephrine, which gives us energy. In fact, epinephrine is made from dopamine. So let's just take a step back and think about what we're talking about when we're talking about sleepiness. If you've ever pulled an all-nighter, you'll notice something interesting. As morning rolls around, you'll suddenly feel an increase in your energy and alertness again, even though adenosine has been building up for the entire night. Why is that? The reason that is, is because there's a second force which is governing when you sleep and when you're awake. And that force is a so-called circadian force. Circadian means about a day or about 24 hours. And inside all of us is the clock that exists in your brain and my brain and the brain of every animal that we're aware of.
That determines when we want to be sleepy and when we want to be awake. That block of sleep and when it falls within each 24 hour cycle is governed by a number of different things. But the most powerful thing that's governing when you want to be asleep and when you want to be awake is light. And in particular, it's governed by sunlight. Now I can't emphasize enough how important and how actionable this relationship is between light and when you want to sleep. It's quite simple on the face of it. And it's quite simple to resolve, but people tend to make a big mess of this whole circadian literature, frankly. So let's just break it down from the standpoint of what's going on in your brain and body as you go through one 24 hour day. Let's start with waking. So regardless of how well you slept at night or whether or not you were up all night, most people tend to wake up sometime around when the sun rises. When you wake up in the morning, you wake up because a particular hormone called cortisol is released from your adrenal glands. Your adrenal glands sit right above your kidneys. And there's a little pulse of cortisol. There's also a pulse of epinephrine, which is adrenaline from your adrenals and also in your brain. And you feel awake. Now that pulse of cortisol and adrenaline and epinephrine might come from your alarm clock. It might come from you naturally waking up, but it tends to alert your whole system in your body that it's time to increase your heart rate. It's time to start tensing your muscles. It's time to start moving about. It's very important that that cortisol pulse come early in the day, or at least early in your period of wakefulness. When you wake up in the morning and you experience that rise in cortisol, there's a timer that starts going, and these are cellular timers, and they're dictated by the relation between different organs in your body, that says to your brain and body that in about 12 to 14 hours, a different hormone, this hormone we're calling melatonin, will be released from your pineal gland. So there's two mechanisms here, a wakefulness signal and a sleepiness signal. And the wakefulness signal triggers the onset of the timer for the sleepiness signal. I'd like to take a quick break and thank our sponsor AG1. AG1 is an all-in-one vitamin mineral probiotic drink with adaptogens. I've been taking AG1 daily since 2012, so I'm delighted that they're sponsoring this podcast. The reason I started taking AG1 and the reason I still take AG1 once and often twice a day is because it is the highest quality and most complete foundational nutritional supplement. 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Now, the way this system works is that you have a particular set of neurons in your eye. They're called retinal ganglion cells. When light comes into the eye, there's a particular group of retinal ganglion cells or type of retinal ganglion cells that perceives a particular type of light and communicates that to this clock that resides right above the roof of your mouth called the suprachiasmatic nucleus. And the suprachiasmatic nucleus has connections with essentially every cell and organ of your body. Now, it's vitally important that we get light communicated to this central clock in order to time the cortisol and melatonin properly. When I say properly, I can say that with confidence because we know based on a lot of evidence that if you don't get your cortisol and melatonin rhythms right, there are tremendously broad and bad effects on cardiovascular health, metabolic effects, learning, depression, dementia. So let's think about what happens when we do this correctly and how to do it correctly. When we wake up, our eyes open. Now if we're in a dark room, there isn't enough light to trigger the correct timing of this cortisol melatonin thing, these rhythms. You might say, well, why won't any light do it? Well, it turns out that these neurons in our eye that set the circadian clock and then allow our circadian clock to set all the clocks of all the cells and organs and tissues of our body, responds best to a particular quality of light and amount of light. And those are the qualities of light and amount of light that come from sunlight. So these neurons, what they're really looking for, although they don't have a mind of their own is the sun at what we call low solar angle.