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. This podcast is separate from my teaching and research roles at Stanford, but is part of my effort to bring zero cost to consumer information about science and science-related tools to the general public.

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Today is episode three of the podcast, Office Hours. During Office Hours, students come to the professor’s office to ask questions, request clarification, or explore topics with more depth and detail. Questions were requested in the comment sections of the previous two episodes of the podcast on YouTube and Instagram. I would like to thank everyone for the excellent questions.

We distilled from that large batch of questions to two types of questions: questions that were asked very often and were light very often with a little thumbs up like tab, as well as questions that we thought could really expand on the topics that we’ve covered previously. Today, we are going to cover both of those. If we did not get to your question, please don’t despair. We will keep track of those and we have several more episodes devoted to this topic of sleep and wakefulness and learning during the month of January, maybe even leaking over a little bit into the month of February.

One of the unique formats of this podcast is that we have time for dialogue, we have time for your questions, and we have time to really go deep into these topics. It’s official, Costello is sleeping in the background. So, if you hear snoring, Costello is going to be keeping time with his deep and melodic snoring. There he goes.

Paragraph 1: So the questions that we received, I batched crudely into a couple of different categories: light, exercise, supplementation, temperature, learning, plasticity, and mood, and sort of mood related disorders. There were a lot of questions about those.

Paragraph 2: Before we begin any of this, I want to point out something that I, I always say it sounds like boiler plate but it’s important not just to protect me but to protect you, which is that I am not a physician. I’m not a medical doctor. I don’t prescribe anything, including behavioral protocols. I’m a professor.

Paragraph 3: So I profess a lot of things based on quality peer reviewed studies. You should take that information. You should filter it through whatever it is that you currently happen to be dealing with, whether or not that’s health or illness, you should consult with a licensed healthcare professional before you add or remove anything from your daily life protocol. I’m not responsible for your health.

A lux is the amount of light that is produced by a single candle at a distance of one meter away. So that’s a beautiful definition.

A lux is the amount of light that is produced by a single candle at a distance of one meter away. Great question, also offers me the opportunity to share with you what I think is a quite beautiful definition of what light is in a quantitative sense. Before we go forward and discuss this many lux or that many lux, I want to just tell you what a lux is. You are, so be smart with this information and be a stringent filter, as we say.

Regarding the role of moonlight and fire in circadian rhythms, somebody asked: Is it okay to view moonlight at night or will that wake me up? Will a fire in my fireplace or using candle light be too much light? I’m presuming they mean fireplace or candle or things of that sort. I’ve mentioned a few times the use of apps and light meters and things to measure things like locks, which sometimes are also described in terms of Kendals. So those are the two units for measuring light intensity. Typically lux, L-U-X is the, is the unit. Okay, very well let’s get started on the actual material.

A lux is the amount of illumination of one square meter surface at one meter away from a single candle. This measurement was decided upon to give a reference or framework for light intensity. For example, 6,000 lux of light intensity would be the equivalent of 6,000 candles all with their light intensity shown on one square meter from one meter’s distance away. Moonlight, candlelight, and even a fireplace do not reset your circadian clock at night, despite seeming very bright. This is because these melanopsin ganglion cells, also called intrinsically photosensitive ganglion cells, in your eye do not detect the same amount of light intensity as the lux measurement.

Cells in our eyes adjust their sensitivity across the day, responding best to the blue-yellow contrast present in the rising and setting sun. This phenomenon, which was discussed in the previous episode, prevents the cells from activating the triggers in the brain that convey daytime signals when they view moonlight, even a full moon. This raises an interesting thought point about lunacy, as there is lore and some quality science around the idea that people act differently when there is a full moon. However, moonlight is typically not going to wake us up too much, except if the moon is really full and bright. Therefore, it is safe to enjoy fireplaces and candles without disrupting your circadian rhythm, as long as it is between the hours of 10:00 PM and 4:00 AM, unless it is necessary for safety or work. I also received a lot of questions about red light.

Now, I think I was asked those questions because red light is used in a number of different commercial products where these products tend to include a sheet of very bright red lights. That one is supposed to view early in the day. And there are various claims attached to these red light devices that they improve mitochondrial function.

I’m going to be really honest and I can’t name brands, and I’m not going to name particular studies. ‘Cause what I’m about to say about these studies is not particularly unkind but let’s just say that none of the studies that I’ve seen, except for one that I’ll talk about in a moment, pointing to the positive effects of red light on the visual system are published in blue ribbon journals. They tend to be published in journals that I had to work hard to find. I’m not sure what the peer review and stringency level is.

Now, that’s not to say red light isn’t beneficial because there is one study in particular that came from Glen Jeffrey’s Lab at the University of College, London it was published last year. Glen is somebody I happen to know is an excellent reputation, excellent vision scientist, what this study essentially showed. And again, this is a study that I very much liked the data and think it was done with very high standards. What this study shows is that, viewing red light for a few minutes each morning can have positive effects on mitochondria in a particular retinal cell type, that tends to degenerate or decline in function with age in humans.

The photoreceptor is a type of cell in the eye that sits at the back of the eye, some distance away from the ganglion cells. It converts light information into electrical signals that the rest of the retina and brain can understand, and without them people are blind. Age related macular degeneration, as well as other factors, can cause the photo receptor functionality to worsen with time. Glen’s study showed that red light flashes delivered early in the day can help repair the mitochondria, although more studies are needed to support this. They are currently doing a clinical trial.

No, you don’t need red lights.

Twelve patients were reported on in regards to potential benefits of red light. The findings were interesting and could lead to potentially useful applications. However, most of the questions asked during office hours were related to the use of red light later in the day. Red light will not stimulate the melanopsin retinal neurons that signal daytime, but the red lights in commercial products are too bright and would wake up the body and brain. If someone decides to use these products, they should do so early in the day to potentially derive benefit on mitochondria function. Red lights are not necessary, but if used later in the day and at night, they should be very dim.

Red lights are convenient because they are bright, but if they are dim, they won’t wake up the circadian clock or disrupt dopamine levels. There is a role for dim red light during the day and at night for mitochondrial repair in the photoreceptors. However, there is no immediate prescription for what type of light to use and when. Blue light is important early in the day and throughout the day, so blue blockers may not be necessary. The melanopsin retinal cells do react to blue light, but this does not necessarily mean that blue blockers are beneficial for preventing resetting of the circadian clock at night.

However, the people that made these products fail to actually read the papers from start to finish, or if they did, they didn’t comprehend a critical element which is that most of those papers early on took those neurons out and put them in a dish. When they did that, they divorced those neurons from their natural connections in the eye. It turns out in your IMI right now, because that’s what we care about, these cells exist and the cells respond to blue light but also to other wavelengths of light because they not only respond directly to light as they do in a dish, they also respond to input from photo receptors.

If you talk to anyone in the circadian biology field, they’ll tell you, “Oh, yeah this blue light thing has really gotten out of control.” People assume that blue light is the culprit because blue light is the best stimulus, however that doesn’t mean that blue light is the only stimulus that will trigger these cells. Like many things a scientific paper can be accurate without being exhaustive, and a lot of claims about products can be accurate, but not exhaustive.

So blue light during the day is great – get that screen light, get that sunlight, especially getting overhead lights. At night, however, you really want to avoid those bright lights.

Light, whether it be blue light or something else, can cause confusion when it comes to product recommendations. While we are on the topic of light, let’s talk about light in other parts of the body. A few people wrote to me after the last podcast episode to ask if light delivered to the ears, roof of the mouth, or up the nose can be beneficial for setting circadian rhythms. The answer is no, not directly. This is a great opportunity to distinguish between the placebo effect and the difference between modulation and mediation. Modulation is when something will change your biology, while mediation is when something will cause a stress hormone to be released. While it might modulate your biology, please don’t put lights up your nose.

Remember earlier in a previous podcast, I said that virtually anything we face can shift our circadian rhythm if it’s different and dramatic enough. So the question is, is it the light delivered through the nose or ears, or some other orifice, that is mediating the process? Is it actually tapping into the natural biology of the system that you’re trying to manipulate? I like to distinguish between real biology and hacks. I don’t like the word hack, or frankly neuro hacking or bio hacking. I just don’t like the term because a hack implies using something for a purpose for which it was not intended. But where you can kind of cheat, that’s not how biology works well. So I try and distinguish between things that really mediate biological processes and things that modulate them.

There are a number of commercial products out there with some studies attached to them, claiming that light delivered to the ears or wherever can adjust your wakefulness or adjust your sleep. I’ve looked at those papers again and I’m probably going to lose some friends by saying this, but maybe I’ll gain a few as well.

Not blue ribbon journals, frankly, oftentimes read the small print. There was a conflict of interest clause there related to commercial interests. If somebody disagrees with me outright on this and can send to me a peer reviewed paper, published in a quality journal about light delivered anywhere, but the eyes of humans that can mediate circadian, rhythms, wakefulness et cetera, I’m more than happy to take a look at that and change my words and stance on this and do it publicly, of course.

But until then I’m guessing that the proper controls were not done of adjusting for heat that could be delivered which can definitely shift circadian rhythms. We’re going to talk about temperature and other things like that. So light to the eyes folks is where these light effects work in humans, in other animals, they have extra ocular photo reception in humans, no.

And just be mindful, I mean, I’m not trying to encourage people to avoid certain products in particular but just be mindful of this difference between modulation and mediation. A mediating, a process through a hard wired or long-standing biological mechanism is really where you’re going to see the powerful effects over time.

I also, as you’ve probably noticed, I really tend to favor behavioral tools and zero cost tools first, and getting those dialed in before you start, plugging in and swallowing and putting things in various places just to really figure out how your biology works and explore that, unless there’s of course a clinical need to take a prescribed drug in which case, by all means, listen to your doctor.

Okay, a huge number of people asked me about what about light through windows?

Setting your circadian clock with sunlight coming through a window is going to take 50 to 100 times longer than usual. I discussed this in a previous podcast with Jamie Zeitzer from Stanford, and I also did an Instagram post about this look. If you want more information, I’d be happy to send you to the various papers that were described.

The key thing here is to do the experiment. You can download the free app Light Meter and take a picture of a bright day outside or some sunlight. It will tell you how many lux are in that environment. Close the window and, if you want, close the screen or don’t open the screen, and you can do all sorts of experiments.

When you look through a window, the light is passing through two pieces of glass, which reduces the amount of light that reaches your eyes. However, when you are wearing prescription lenses or contacts, the light is only passing through one layer of glass, so the amount of light reaching your eyes is much higher and more effective.

Lenses that you wear in front of your eyes, either by prescription or on your eyes, are designed to focus the light onto your neural retina. Near-sightedness is when the image falls in front of the neural retina, and wearing a particular lens in front of that focuses the lens onto the retina and these very neurons so they can communicate that to the brain. Costello is loving this light and is deep in sleep, and if we play him some tones, he may remember it later. Prescription lenses are great for this reason as they are actually focusing the light onto the retina. Logically, it makes perfect sense that your glass window, windshield, or side window of your car is not optically perfect to bring the image and the light onto your retina.

Light is important for our bodies to recognize when it is day and night. We discussed this in the previous podcast. To make sure our bodies are getting the right signals, we need to be outside for longer or use bright lights inside. This will help us to change our behaviors depending on the time of year and other lifestyle factors. Early in the day, our bodies need a lot of light to trigger an alertness signal. This is when the sun is low in the sky and even if it is not that bright outside, we should stay outside longer. For example, someone sent me a picture of their walk in England and the light meter showed 700 lux or less, so I suggested they stay outside longer.

Turn on the lights really bright, particularly the overhead lights, as these will be best for stimulating the mechanisms in the eye and the brain. For the first few hours of the day, this will allow for photon activation of the cells. In the middle of the day, however, once the sun is overhead, or even if you stay inside all morning, you will enter the “circadian dead zone” which is not ideal. No matter how much artificial or natural light you get, you will not be able to shift your circadian clock or get a wake up signal. In the evening, be aware that even a few photons of light can be detrimental to melatonin production. To protect against this sensitivity, look at the setting sun and watch the evening sun, even if it is not crossing the horizon. This will adjust your retinal sensitivity and melatonin pathway so that light is not as damaging to melatonin at night. Think of this as a “Netflix inoculation” which will allow you to watch a little bit of Netflix in the evening.

There seems to be some other neuro-biological process going on where I have to watch episode after episode after episode. To protect myself against the bad effects of light at night, I can look at light in the evening which adjusts down the sensitivity of the system.

I want to talk about seasonal changes in mood and metabolism. Depending on where you are in the world, the days and nights are going to be different lengths. This translates to real biological signals that impact wakefulness, sleep times, mood, and metabolism. Every cell in your body is tuned to the movement of the planet relative to the sun.

The Earth spins once every 24 hours on its axis and travels around the Sun in 365 days, which is one year. The Earth is tilted on its axis, so depending on where we are in the Northern or Southern hemisphere, some days of the year are longer than others. At the equator, there is less variation in day length and night length. Closer to the poles, there are some very long days.

Depending on the time of year, days can either be getting shorter or longer. Every cell in the body can adjust its biology according to the day length, except for the brain, body and cells. This is because they only measure night length. Light powerfully inhibits melatonin, and if days are long and getting longer, the total amount of melatonin is reduced. On the other hand, if days are getting shorter, light can’t inhibit melatonin as much, causing the melatonin signal to become longer. Therefore, every cell in the body can measure external day length and the time of year by the duration of the melatonin signal.

In diurnal animals, such as humans, the longer the melatonin signal, the more depressed our systems tend to be. Reproduction, metabolism, mood, and turnover rates of skin and hair cells all tend to be diminished compared to the spring and summer months when days are very long. During these times, there is less melatonin, and in almost all animals, including humans, there is more breeding, hormone elevation, and increased metabolism.

Some people are very strongly tied to the seasons and get clinically depressed in winter, for which light therapies are very useful. Conversely, some people love the winter and feel depressed in summer, although this is far more rare. That doesn’t mean depression cannot exist in the summer, but when we’re talking about seasonal depression, that tends to be true.

It’s more common to experience depression in winter. Other things that correlate with seasonality include suicide rates, which tend to peak in the spring. This is due to the complicated and tragic aspects of suicide, where people often commit suicide as they are emerging from a low energy state, rather than at the depths of their energy levels. We will discuss suicidality and mood disorders in a later podcast season.

It is important to understand that everyone goes through natural fluctuations depending on the duration of the melatonin signal. Unfortunately, it is not possible to reduce melatonin levels all the time in order to feel great all the time, as melatonin also has important effects on the immune system, transmitter systems in the brain, and so on. Everyone needs to find the right balance of light early in the day and late in the day to optimise their mood and metabolism. This is because there are a range of melatonin receptors, metabolic types, genetic histories and family histories, so there is no one size fits all prescription.

By understanding that light and extended day length inhibit melatonin, which is associated with depressed or reduced functioning of activity driving and mood elevating signals, you have some control over melatonin by way of light, including sunlight and artificial light. This should empower you to make the adjustments to ensure you are getting enough light if you are feeling low.

Melatonin is synthesized from serotonin and is important for restoring mood. It should not be taken across the board, as it is necessary to fall asleep and stay asleep. Serotonin is a neurotransmitter associated with feelings of well-being when provided to proper levels. This feeling comes from activities such as having a good meal, spending time with friends, and bonding with a loved one. Serotonin does not stimulate action, but rather tends to stimulate stillness.

Light is a powerful signal for modulating things like sleep and wakefulness, serotonin levels, and melatonin levels. Exposure to bright light in the middle of the night can reduce dopamine levels, leading to problems with learning, memory, and mood. To avoid these issues, it is best to avoid bright light in the middle of the night. Seasonal rhythms have a number of effects, but humans are not purely seasonal breeders–we breed all year round. In fact, there is a preponderance of September babies, which suggests that they were conceived in December.

In December, in the Northern hemisphere, days tend to be shorter and nights tend to be longer. Humans are not seasonal breeders, though there can be shifts in breeding and fertility. These effects vary from person to person. Everyone should try to get adequate sunlight and avoid bright light at night throughout the year. Throughout this podcast and in previous episodes, I have mentioned neuromodulators such as serotonin, dopamine, and epinephrine. These neuromodulators influence certain brain circuits and can lead to the feeling of being stressed when released in high amounts. When asked about the difference between epinephrine and adrenaline, adrenaline is secreted from the adrenal glands which sit above the kidneys.

Epinephrine (also known as adrenaline) is a molecule released within the brain. People often use the terms “epi” and “neph” interchangeably; “epi” meaning near, or on top of, and “neph” meaning kidney. Originally, the term epinephrine was used to describe adrenaline, which is the same molecule. Epinephrine and adrenaline stimulate agitation and the desire to move.

Exercise is closely related to sleeping well. Questions such as what forms of exercise are best and when to exercise are often asked.

There are basically two forms of exercise that we can talk about: cardiovascular exercise, which involves repeating a movement continuously (e.g. running, biking, rowing, and cycling), and resistance exercise, which involves lifting progressively heavier and heavier weights. Cardiovascular exercise is typically more aerobic in nature, while resistance exercise is more anaerobic. Most studies of exercise have looked at aerobic exercise, as it is something that can be done with rats and mice. Remarkably, rats and mice have been found to love aerobic exercise, as they are drawn to running wheels with the passage of the visual image of the bars in front of their face.

Most of the studies on mice that love running on wheels have been done in laboratory conditions, making it challenging to do weight bearing exercise studies. Therefore, studies looking at these two things have to be done in humans, as we are interested in them. It is suggested that aerobic exercise is best done in the morning and weight training is best done in the afternoon, however, there is a lot of individual variation. The exercise science literature and the circadian literature point to two windows in which performance, injury, etc. is optimized: 30 minutes after waking, which probably correlates with the inflection in cortisol associated with waking, and three hours after waking, which is when body temperature tends to peak. The later afternoon, usually 11 hours after waking, is also when temperature tends to peak.

Some people like to exercise in the morning, while others prefer the afternoon. It really depends on personal preference and schedule. For those with busy lives, it is advantageous to be able to work out whenever you have the opportunity. However, studies have shown that working out 30 minutes after waking, three hours after waking, or 11 hours after waking can optimize performance and reduce injury. That being said, it is important to figure out what works best for you. Additionally, if you exercise first thing in the morning, your body will develop an anticipatory circuit that will lead you to want to wake up at that particular time.

Light exposure and exercise are both important for wake-up signals to the brain and body. People should be aware that intense exercise late in the day may cause difficulty sleeping. Research has found that if one is not feeling rested and recovered, despite sleeping the same amount they typically have, it is likely that the intensity of exercise in the preceding two or three days was too high. Andy Galpin or another exercise scientist should be consulted for further advice. Finally, it is important to note that any advice on exercise or nutrition may be challenged as there is support for almost any protocol in the literature.

I looked at two journals in particular, International Journal Chronobiology and journal Biological Rhythms, to assess parameters related to neural plasticity. Neural plasticity is the brain and nervous system’s ability to change in response to experience. It was asked whether or not these deep biological mechanisms around wakefulness, time of waking sleep, et cetera, were subject to neuroplasticity and indeed they are. Some of that plasticity is short-term and some of it is more long-term. There is a good analogy of this: if one were to eat on a very tight schedule for a couple of days, they would start to anticipate those meal times and even feel a little agitated before them. This is because of peptide signals that come from the periphery of the body, such as hypocretin orexin, that signal to the hypothalamus and brainstem to make one active and alert to look for food and feel hungry. Eventually over time, the neurons and neural circuits that control hypocretin orexin would get tuned to the neural circuits that are involved in eating, smell and taste to create an eating circuit that is unique to one’s pattern and rhythms.

The same thing is true for waking and exercise schedules, as well as all trade-in schedules. If you wake up in the morning and start getting your sunlight, or exercise in the morning or the afternoon, your body will start to anticipate that and secrete hormones and other signals that prepare your body for the activity. Even if the 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 or exercise at a particular day.

To increase plasticity, there are two forms. One is plasticity that we can access in sleep to improve rates of learning and depth of learning. The other is SDR (non-sleep deep breaths) that can be done without sleeping, to improve rates of learning and depth of retention. Both of these protocols are based on quality peer reviewed studies and can be incorporated if desired.

Learning in sleep is based on some work published in the journal Science. Matt Walker also talks about these studies in his book “Why We Sleep”. In the study, individuals were brought into a laboratory and Lowe did a spatial memory task. This involved a screen with different objects popping up in different locations. It was difficult to remember if something presented in a given location was something seen before and whether it was presented in that location or a different location. Subjects either 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. During the sleep of those subjects the same odor or tone was played while they were sleeping for several nights.

They did an experiment where they tested the effect of providing a stimulus (odor or tone) while subjects were asleep on the rate of learning and retention of information. They found that when the same stimulus was provided while the subjects were asleep, the rates of learning and retention of information was significantly greater. This means that it is possible to cue the subconscious and asleep brain to learn particular things better and faster. To implement this, one could play with the experiment and see what works best.

I don’t see any real challenge to this provided the odor and is a safe one and then doesn’t wake you up. 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. There are a number of groups I think now that are trying this using tactile stimulation. So slight vibration on the wrist during learning and then the same vibration on the wrist during sleep. It does not appear that the sensory modality, whether or not it’s odor or auditory tone or tactile stimulation, some as a sensory stimulation, whether or not it matters. It’s remarkable because it really shows that sleep is an extension of the waking state. We’ve known that for a long time, but this really tethers those two in a very meaningful and actionable way. So I think I’ll report back to you as I learn more about these studies, but that’s what I know about them at this point. As long as we’re there, we might as well talk about dreaming ’cause I got so many questions about dreams.

Dreams can be interpreted in many ways, and there is some controversy around what they mean. I don’t even know what my dreams mean half the time. However, if you want to remember your dreams better, you can set your alarm to wake you up during the REM cycle of sleep. This is usually the last 90 minutes of the night, and is when most dreams occur. Writing down your thoughts immediately upon waking can also help you to remember your dreams. Ultimately, the meaning of dreams is up to the individual to interpret.

Some people believe that dreams have strong meaning, while others believe they are just spontaneous firing of neurons that were active in the waking state and don’t have any meaning. Data suggests that when we learn new spatial environments, the place cells that fire in the brain when entering a particular environment are replayed in sleep.

Sleep paralysis is another phenomenon related to dreaming. We are typically paralyzed during sleep, so-called atonia, presumably so we don’t act out our dreams. Some people wake up and are still paralyzed, which can be quite frightening. From personal experience, waking up wide awake but unable to move the body is very frightening.

There are a couple of things that can increase the intrusion of atonia into the wakeful state, which is essentially when you’re waking up but can’t move. One of these things is marijuana, THC. I’m not a marijuana smoker, so I’m not saying one way or another about its legality. The fact that I had the experience without marijuana means that it can happen regardless. Marijuana smokers report a higher frequency of this kind of paralysis and wakefulness as they transition from sleep to wakefulness. It is unclear why this is, but it could have something to do with cannabinoid or serotonin receptors downstream of the motor pathways. I suppose one could learn to get comfortable with it, as it was quite a terrifying experience for me, not being able to move my limbs.

Non-sleep deep rest (NSDR) and short 20-minute naps have been shown to increase rates of learning. These short naps, which are close to NSDR, are rarely deep enough for someone to enter a deep state of sleep, unless they are very sleep deprived. NSDR and naps are taken immediately after, or close to, the end of a period of learning. A study published in Cell Reports last year showed that taking these short naps or NSDR immediately after learning accelerates learning to a significant degree. This is due to 90-minute ultradian cycles, which involve transitioning into a focus mode early in the cycle and then transitioning to a period of non-sleep deep rest by the end of the cycle.

Paragraph 1: Both the amount of information and the retention of that information can be accelerated without drugs or extra sleep through the use of 20 minute bouts every 90 minutes of ultradian learning cycles. This could be motor, cognitive, or musical learning.

Paragraph 2: To help with this process, links to two different yoga nidra and hypnosis protocols from the Stanford Psychiatry Department were provided in the last episode of the YouTube caption. Additionally, there are many other hypnosis scripts available, such as those by Michael Sealey, which are designed to be clinical and not stage hypnosis.

Hypnosis is designed to help rewire your brain circuitry. This has a lot to do with sleep, as it engages neuro-plasticity by bringing together two things that normally are separate from one another: the alert, focused, wakeful state where you activate the learning and the deep rest where the actual reconfiguration of the neurons and synapses takes place. Hypnosis brings both the focus and the deep rest component into the same compartment of time, creating a very unique state. This maximizes the learning and the non-sleep deep rest and combines them. However, this requires some guidance from a script or from a trained hypnotist. Hypnosis is more about shifts in state, such as fear to states of calm or smoking to quitting smoking, and anxiety around a trauma to release of anxiety around a trauma, rather than specific information learned in hypnosis. It is more about modulating the circuits that underlie state as opposed to specific information.

Do you want to be faster? Okay, maybe you need to work on your sprints.

Although I would not be surprised if there weren’t certain forms of hypnosis that could increase retention and learning of specific information, I’m not aware of any of those protocols out there yet. This brings us to the next thing about learning and plasticity which is nootropics, AKA smart drugs. [Sighs] This is a big topic and that sigh was a sigh of concern about how to address nootropics in a thorough enough, but thoughtful enough way.

Look, I have a lot of thoughts about nootropics. First of all, it means smart drugs, I believe. And I don’t like that phrase because let’s just take a step back and think about exercise. You just say, I want to be more physically fit. What does that mean? Does it mean I would ask for more specificity, I’d say, do you want to be stronger? Okay, maybe you need to lift heavier objects progressively. Do you want to be faster? Okay, maybe you need to work on your sprints.

Do you want more endurance, flexibility, explosiveness, or suppleness? There is a huge range of things that we call physical fitness, and maybe you want all of them. When it comes to emotional fitness, it is important to be able to feel empathy and to disengage from it when necessary. It is also important to be able to access a range of emotions, but for some people, their range into the sadness regime might be much greater than their range into the happiness regime. On the other hand, some people might be able to access all the happy stuff but not the sadder stuff. It is important to be aware of these different ranges when considering emotional fitness.

Paragraph 1: But if we say we’re talking about cognitive and cognitive abilities we have to ask, okay, creativity, memory. We tend to associate intelligence with memory. And I think this goes back to like spelling bees or something, the ability to retain a lot of information and just regurgitate information which will get you some distance in some disciplines of life.

Paragraph 2: But it won’t allow you creative thinking, it’s necessary for creative thinking. You need a knowledge base, right? You can’t just look up everything on Google, despite what you know, certain educators or so-called educators say, you need a database so that you can have the raw materials with which to be creative.

Paragraph 3: So necessary to have memory but not sufficient to be creative, right? The creative could have a poor memory for certain things but certainly not for everything. They can’t have anterograde and retrograde amnesia. They’d be like the goldfish that every time around the tank, it, you know I can’t remember where it’s at.

The idea that I have with the concept of a nootropic or a smart drug is that it’s not specific as to what cognitive algorithm you’re trying to engage. We need more specificity. That said, there are elements to learning that we’ve discussed here before that are very concrete things like the ability to focus and put the blinders on to everything else that’s happening around you and in your head mainly. This is required for triggering the acetylcholine neuromodulator that will then allow you to highlight the particular synopsis that will then later change in sleep. However, no nootropic allows you to bypass the need for sleep and deep rest. This is important to understand.

So I daydream about a day when people will be able to access compounds that are safe, that will allow them to learn better meaning, to access information, focus better, as well as to sleep better and activate the plasticity from the learning about. Right now most nootropics tend to bundle a bunch of things together.

Most of them include some form of stimulant, caffeine. Episode two, I’ll tell you more probably than you ever wanted to know about caffeine, adenosine and how that works. So refer there for how caffeine works. But stimulants will allow you to increase focus up to a particular point.

If you have too little alertness in your system, you can’t focus, too much however, you start to cliff and focus drifts, okay? So you can’t just ingest more stimulant to be more focused. It doesn’t work that way. Most nootropics also include things that increase or a desire to increase acetylcholine.

Nootropics are compounds that are purported to increase focus and alertness. Evidence suggests that they can increase acetylcholine levels, and websites such as Examine.com can be used to evaluate their safety and effects. Traditionally, epinephrine has been used to increase alertness and compounds such as alpha GPC to increase acetylcholine. However, these stimulants can lead to a crash that does not provide the restful sleep necessary for learning and memory. Therefore, my stance on nootropics is that they should be used only occasionally and cautiously, as their shotgun approach is unlikely to be beneficial in the long run.

A lot of people ask about Modafinil or Armodafinil, which was designed for the treatment of narcolepsy. It is a stimulant and there is evidence that it can improve learning and memory. Modafinil is very expensive, but there is a generic version available that is far less expensive. It is similar to amphetamine and has the potential for addiction or can be habit forming. It can also disrupt insulin receptors and other metabolic effects, so it should be approached with caution. There are milder nootropics available, such as alpha GPC and Gingko, that may be more suitable.

I suffer from vicious headaches when taking Gingko, so I don’t take it. Last podcast, I recommended magnesium threonate as an option for people exploring supplements. I’m not recommending anything directly, but magnesium threonate seems to be among the more bioavailable and useful for sleep. I recommended it to a good friend of mine, however, he had stomach issues with it and had to stop taking it. He experienced stomach cramping and it just didn’t feel good. Other people take it and feel great.

When taken 30 to 60 minutes before sleep, magnesium threonate should be taken without food. It is designed to make you sleepy, but it is important to consult with a doctor before taking it. Many people have benefited from magnesium threonate, but some people cannot tolerate it. Apigenin is another supplement that can be taken to access deep sleep and neuroplasticity. It increases enzymes associated with GABA metabolism, which is an inhibitory neurotransmitter that is increased after a couple of drinks containing alcohol.

Apigenin is a derivative of the camomile which has a proper pronunciation of metric caria kemo mila. Although I always feel like I should be using a Spanish accent when I say it. Apigenin and passion flower, which is [speaks in foreign language], are found in a lot of supplements designed to increase sleepiness and sleep because they work presumably because they increase GABA. I don’t know why the Italian, is that Italian? My Italian colleagues, please forgive me, I have some very close Italian friends and colleagues in Genoa, but I butchered the Italian, sorry.

Chloride channels are responsible for neurons becoming active when sodium ions, or salt, rush into the cells and cause them to fire electrically. The cells become less active as chloride, a negatively charged ion, enters. This is likely taking some back to high school physics, as chloride carries a negative charge and hyperpolarizes the neuron. Apigenin and passionflower work by increasing the activity of these chloride channels and GABA transmission. This increases the inhibitory neurotransmitter, which shuts off our thinking and analysis of duration, path, and outcome. If one is going to explore these things, they should at least know how they work and talk to their doctor about them. Examined.com is also a good resource.

Some people asked about serotonin for getting to sleep and staying asleep. Just like I understand the rationale of taking something like Macuna Purina or L-DOPA to increase dopamine, sometimes what works on paper doesn’t really work in the real world. I personally have tried taking a supplement which was Al tryptophan, which is the precursor to serotonin, or five HTP, which is designed to increase serotonin. You’re just a one biochemical step away from actually taking actual serotonin.

I’ll be honest the sleep that I had with increased serotonin by way of tryptophan or five HTP was dreadful. I fell asleep almost immediately, but 90 minutes later, I woke up and couldn’t sleep almost for 48 hours. Now that was me, I have a pretty sensitive system to certain things and not to other things.

Some people love these things, so you really have to be thoughtful and explore them with that kind of awareness of being thoughtful and realizing that what works for you might not work for everybody, and what works for everybody might not work for you.

I’d like to continue by talking about the role of temperature in sleep, accessing sleep, staying asleep and wakefulness. But first, I want to tell a joke. I think this joke really captures some of the critical things to understand about any self-experimentation that you might do.

This is a story that was told to me by a colleague of mine who’s now a professor of Caltech (not to be named). So there’s a scientist and they’re in their lab. They go over to a tank and they pick up a frog, take the frog and put it down on the table and they clap.

The researchers observed that when they injected a paralytic drug into the back legs of a frog, the frog was no longer able to jump. To further prove their hypothesis, they injected the drug into the remaining two legs and the frog was no longer able to jump. They concluded that the legs of the frog were responsible for hearing, and they published their findings in a great journal with accompanying news releases.

It’s a really big deal when their career takes off. Twenty years later, a really smart graduate student comes along and says, “Yeah but that’s loss of function. It doesn’t really show gain of function.” To take a closer look, they repeated the first experiment and checked out that everything happened the same way. They then injected a drug into all four legs of the frog that turns off the paralytic, an antagonist. When they set the frog down and clapped, it jumped, leading them to realize that the legs were indeed for hearing.

This is not to suggest that science is not a good practice, as it is. We need to do loss of function and gain of function experiments to understand correlation and causation, which is complicated. Control experiments need to be done and we need to figure out what works for us.

Science can provide answers about what works under very controlled conditions, but it cannot and never will address all the situations in which a given compound or practice will or won’t work. This is due to individual variability and a number of different factors including light, exercise, and food, which can all activate and shift our circadian rhythm. To conclude, I want to make an important point that no frogs were hurt in the telling of this joke.

Now, I want to talk about temperature and its relation to circadian rhythms, wakefulness, and sleep. Generally, our body temperature is lowest around 4:00 AM and starts to increase around 6:00 AM, 8:00 AM and peaks between 4:00 PM and 6:00 PM.

Different people have different normal body temperatures, but in general, if we were to continuously or occasionally monitor temperature, we would see an oscillation or rhythm in our temperature, going from high to low. This is why the idea that everyone has a correct temperature of 96.8 is false. The normal range varies depending on the time of day temperature is measured, but a fever is usually considered to be somewhere around 100-103.

We will be very concerned if the temperature drops too low. The way our temperature rhythm, which is endogenous and rhythmic, gets anchored to the pattern of being lowest at 4:00 AM and increasing again around through the day until about four to 6:00 PM is by way of entrainment or matching to some external cue, usually light and exercise. We may have experienced this temperature rhythm and how quickly it can become uninterested or fall out of entrainment. An example of this is when we stay in doors and don’t get enough light, we may start feeling chilled around 10 or 11 o’clock. This is because the oscillators in our various tissues that are governed by temperature and circadian rhythm start to split away from our central clock mechanisms. It is important that our temperature matches day length. Additionally, as days get longer, it tends to be hotter out.

Temperature and day length are linked metabolically, biologically, and atmospherically. One of the most powerful things about setting your circadian rhythm properly is that your temperature will start to fall into a regular rhythm, which has a very strong effect on things like metabolism. 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 – 30 minutes after waking, as well as three hours after waking, and when temperature actually peaks – generally about 11 hours after waking. Therefore, temperature and circadian rhythm are even more linked than previously thought.

Light enters the eye, triggering activation of melanopsin cells, which then triggers activation of the super charismatic nucleus, the master circadian clock. This master clock informs all the cells and tissues of the body, putting them into a nice cohesive rhythm. How does it do this? It does this in two ways: by secreting a peptide, a little protein that floats through the bloodstream and signals to the cells, and by synchronizing the temperature under which those cells exist. Temperature is the effector of the circadian rhythm.

Changes in temperature, especially by way of exercise, can significantly shift our circadian rhythm. There is some interest in cold showers and ice baths, although people seem to either love or hate it. I personally don’t mind it and have taken people to a cold dunk or an ice bath. However, I have a family member who wouldn’t even get in past her toes!

She was like, “This is just too aversive for me. Some people really like the cold, but people vary tremendously. Getting into an ice bath is very interesting because you have a rebound increase in thermogenesis. Now, you should know from the previous episode that as that temperature increases, it will shift your circadian rhythm. The direction it shifts your circadian rhythm will depend on whether you’re doing it during the day or late in the day. If you do it after 8:00 PM, it’s going to make your day longer because your body and your central clocks are used to temperature going up early in the day and peaking in the afternoon.

If you then increase that further or you simply increase it over its baseline at 8:00 PM after temperature was already falling, even if it’s just by a half a degree or a couple of degrees or you do that with exercise (doesn’t have to be with the ice bath), you are extending, you are shifting forward your phase, delaying your clock. You’re convincing your clock 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.”

You might say, “Wait, I do an ice bath late at night and I feel great. And I fall deeply asleep.” Well, cold can trigger the release of melatonin which can cause a rebound increase in melatonin. This could be the cause of the effect. However, if you do the ice bath or cold shower early in the day and then get out, you will experience a more rapid rise in your body temperature that will phase advance your clock and make it easier to get up early the following day.

It might sound laughable, but a cold shower first thing in the morning will wake you up in the short term, as well as shifting your clock and making you more likely to get up earlier the next day. Increasing your temperature by getting in an ice bath or cold shower or exercising causes a compensatory increase in body temperature. This normal pattern of body temperature starts to increase right around waking and then peaks around 4-6 PM before dropping off. If you introduce an increase in body temperature by way of cold exposure early in the 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.

Temperature is not just one tool to manipulate wake up time and circadian rhythm and metabolism. It is the effector, the way that the central circadian clock impacts all the cells and tissues of your body. If you want to read further about this, you can Google the work of Joe Takahashi who used to be at Northwestern University and is now at UT Southwestern in Dallas. He is an incredible scientist and has really worked out a lot of the mechanisms around temperature in circadian rhythms.

I also want to talk about cold and cold exposure because there’s a great misconception about this that you can leverage once you understand how to use cold to either increase thermogenesis and fat loss, metabolism, or you can use it for stress mitigation and mood. It really depends on one simple feature of how you approach the ice bath or cold shower.

Using cold exposure to calm the autonomic nervous system involves various tools and techniques. People can pay attention to an external stimulus, or directly experience the cold in its most intense form. There is no right or wrong way to go about this, but the goal is to suppress the activation of the sympathetic nervous system, meaning the alertness or stress system, and to buffer or resist the shiver response. This will help to raise the stress threshold and better tolerate heightened levels of real life stress.

The shiver response is an autonomic response designed to generate heat in order to counter the cold. When cold exposure is used as a form of stress inoculation, it works quite well for that purpose. It is also used in a variety of forms of military stress inoculation, most famously in the Navy SEALs’ “BUDs” screening procedure.

If cold exposure is used for fat loss and thermogenesis, however, the opposite approach should be taken. A paper published in Nature two years ago showed that the physical shiver activates the release of a chemical in the body called succinate, which travels in the bloodstream and activates a particular category of fat called brown fat. Brown fat is dark under the microscope and is rich with mitochondria. It exists mostly between the scapulae and in the upper neck.

The body has certain categories of agile anergic receptors that bind to epinephrine and cause Brown fat cells to increase metabolism, known as Brown fat thermogenesis. This process can burn pink and white fat. There are three ways to use an ice bath or cold shower to shift one’s circadian rhythm. One can do it early in the day while the temperature is still rising or at its peak, or after the peak in order to extend the perception of the day. The third way is to activate Brown fat thermogenesis and increase metabolism.

There are four ways to shift one’s circadian rhythm: increasing stress tolerance or stress threshold, exposure to light, the super charismatic nucleus as the master circadian clock, and eating according to the local meal schedule. Temperature is the effector of circadian rhythms, while light is the trigger. Additionally, non-photic influences such as exercise and feeding can also influence the circadian rhythm. Eating can also shift one’s circadian rhythm more quickly, likely due to changes in temperature inducer and eating-induced increases in body temperature.

Light and temperature are the real heavy duty leavers when it comes to moving your circadian rhythm and sleep times and activity schedules. Exercise and feeding can help, but really temperature and light, with light being the primary one, are the most important when it comes to sleep and wakefulness. Many people asked questions about food and neurotransmitters and how those relate to sleep, wakefulness and mood. Tryptophan is a precursor to serotonin and it comes from the foods we eat. Beta and hypercretin orexin are anticipatory secretions that I discussed earlier. In episode four of how to shift one’s rhythm, I will get more into this. If this is getting a little too down in the weeds, don’t worry about it.

Tyrosine is the precursor to dopamine and is found in the foods we eat. Once ingested, these compounds are circulated to different cells and tissues. It is possible to influence neuromodulator levels to some extent by the food we eat, but this is not the only way as there are also enzymes and biochemical pathways that regulate the conversion of tyrosine to dopamine. Foods rich in tyrosine, such as red meats and nuts, tend to lead to the production of dopamine and other wakefulness associated hormones. The volume of food we eat also impacts our wakefulness. Fasting states are generally associated with more alertness, while fed states are associated with quiescence and relaxation.

Foods that are rich in tryptophan, such as white meat and turkey, can be used to experiment with carbohydrate-rich meals for accessing sleep and more depth of sleep. This is something I personally do. I tend to fast until around noon and then have a low-carb meal. Unless I have worked out extremely hard in the previous two hours, in which case I may have a higher-carb meal to prolong my period of wakefulness into the late afternoon.

Sometime around dinner time, which for me is around 6:37 PM, 8:00 PM or sometimes as late as 9:00 PM, I tend to eat things like white meat, fish, pastas, rice, and other similar foods. My favorite food for accessing tryptophan is actually a starch and a vegetable: the croissant. I don’t eat them all the time, but I love them and they seem to increase dopamine as well. Low carbohydrate/fasted/ketogenic diets tend to lend themselves toward wakefulness by way of increasing epinephrine, norepinephrine, adrenaline, dopamine, and things of that sort. On the other hand, carbohydrate rich meals tend to lend themselves more toward tryptophan, serotonin, and more lethargic states.

There is limited evidence that carbohydrates should be eaten at one time a day as it relates to metabolism, et cetera. However, this can change depending on the person’s activity level; for instance, those who work out hard and deplete glycogen stores may need to adjust their eating habits. Furthermore, different foods can bias different neuromodulators and affect our feelings of wakefulness and sleepiness.

Eating itself can also have a powerful effect on circadian rhythms and wakefulness. This is due to eating induced thermogenesis, which is an increase in metabolism and temperature that is greatest for amino acid-rich foods. The increase in temperature is minimal, ranging from a quarter of a degree to a degree, depending on the individual.

There are blood sugar effects when it comes to food. Type one and type two diabetics, as well as those who are insulin resistant, will be affected differently. For example, a teenager like the intern on the podcast here, who can seemingly eat anything and still grow, will be affected differently than a full-grown person. Generally, starchy carbohydrates, white meat like turkey, and some fish increased tryptophan, therefore serotonin, leading to more lethargic states and a calmer mood. Meat, nuts, and some plant-based foods high in tyrosine can increase dopamine, norepinephrine, and epinephrine, leading to more alertness. Most people are eating a variety of these things in a given meal.

There are other parameters of nutrition that are important too. Volume of food, for the reasons I mentioned before, will tend to correlate with wakefulness. Large volumes of food of any kind will tend to correlate and drive the calming response. This is done through a nerve pathway called the vegas. Sensory fibers in the gut communicate to a protrusion of neurons called the nodose ganglia. This then goes into the brain stem and forward in the brain to the areas involved in production of various neuromodulators. It is not just the food we eat, but also the volume of food that is signaling to the brain. Additionally, there is eating-induced thermogenesis.

Eating early in the day can shift one’s rhythm earlier, making them want to wake up earlier the next day. Conversely, eating late in the day can cause one to want to sleep later the next day. However, this is all dependent on external factors, such as when family members need to eat, or what other activities one is doing. Some people are very rigid with their meal schedule, while others are not. For example, one may take their light exposure schedule more seriously than their meal schedule. In general, it is important to try and eat healthy foods, including the occasional croissant.

Men and women (or males and females) differ in terms of neurotransmitter phenotypes, rhythms of sleep and temperature, and other biological variables. This has been explored in more detail recently, as the National Institutes of Health (NIH) has made it a mandate that all studies use sex as a biological variable and explore both sexes of mice and humans. As a result, important sex differences have been revealed which can have a powerful impact on health practices and the response to drugs and different sleep schedules. Pregnancy and childbirth are perhaps the most salient and obvious examples of sex differences, and for this we will need to bring in experts to explore in more depth.

As we finish up, I just want to offer you the opportunity to do an experiment. We’ve talked about a lot of variables that can impact sleep and wakefulness, and in keeping with the theme of the podcast, we are going to continue to talk about sleep and wakefulness and tools for those, and the science behind those tools as we go forward.

There are really just four simple parameters that you have control over that you can immediately start to record and take note of just to see how you’re doing with these things, with no judgment or perhaps no change to what you’re actually doing. 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 waking.

The way I do this in my calendar is I’ll write down that I don’t get exact about it. I might say, I woke up at 6:15 and then I, as I’ll put a W 6:15, and then SL for sunlight and you’ll sometimes get outside right away. Other times I’m less good at that and I’ll go out around, let’s say seven and for how long, I don’t maybe like 10, 15 minutes or so.

I’ll put a little check at the times that I eat my so-called meals. Sometimes my meals are a bunch of small checks that just kind of extend through the late hours of the day. Yours might be more confined to certain times. You might take note of when you exercised, just putting down an “E” for when you do weight training or aerobic exercise. You might also note when you felt chilled or cold, or particularly hot, or if you woke up in the middle of the night feeling particularly hot. Lastly, you might want to write down if and when you did a non-sleep deep rest protocol, such as meditation, yoga nidra, or hypnosis. Anything you use to deliberately teach your nervous system how to go from more alertness to more calmness in the waking state, even if it’s waking up in the middle of the night and doing an SDR protocol, or in the afternoon, or first thing in the morning to recover some sleep and ability to perform DPOs that you might’ve lost from a minimal or poor night’s sleep. To do this, you can use a simple record keeping scheme like “W” for waking, “SL” for sunlight, and a check or an “X” for exercise. This is not designed to make you neurotically attached to tracking all your behaviors and everything you do.

I for instance, don’t track what I eat. In particular, I kind of know what works for me and I’d just try and stay within that range. But by doing this, you can start to reveal some really interesting patterns. Patterns that no answer that I could provide you about any existing tool or protocol could counter. It’s really about taking the patterns of behaviors, of waking, light viewing, eating, and exercise, and superimposing that on what you’re learning in this podcast and elsewhere of course, and what you already know, and trying to see where certain problem or problems or pain points might be arising. Maybe you’re eating really late in the day and you’re waking up in the middle of the night, really warm. Well, now you would say, “Well, that could be due to kind of an increase in temperature that is extending my day.” Or maybe you start to find that using cold exposure early in the day is great for you, but using it late, if it’s too late in the day, that’s not great. Or if you’re into the sauna or it’s even like some people, including myself, if I take a hot shower or sit in a hot tub or a sauna late at night, well then I get a compensatory decrease in body temperature and I sleep great provided I hydrate well enough, ’cause that can be kind of a dehydrating thing to sit in hot, hot conditions. But if I do the sauna early in the day, unless I exercise immediately afterward, then I tend to get the temperature drop, which makes sense because when you get in the sauna, you’re get vasodilation. You throw off a lot of heat and then you generally get a compensatory drop in temperature.

Starting your day early is a great way to entrain your body’s circadian clocks. Everyone’s body is slightly different, so I suggest experimenting to find the variables that work best for you. Manipulate one or two variables at a time, and do so slowly and carefully. As always, thank you for your questions. We will continue to answer them.

Episode four of the podcast will cover shift work, jet lag and age dependent changes in sleeping and wakefulness and cognition. For those of you with kids, older relatives or who might be older, we will talk about biological shifts in temperature regulation and things that relate to sleep. Additionally, for those of you who travel, we will discuss jet lag. We will also discuss how most people are now in a form of shift work due to their interactions with devices, and how this affects their sleep and alertness. Finally, I will touch back on a few of your questions and thank those of you who have asked how you can help support the podcast.

You can support the podcast by liking it on YouTube, subscribing on YouTube, and recommending the YouTube videos to others. Additionally, you can subscribe and download the podcast on Apple, where you can also leave a review, and on Spotify, where we are available on all three platforms. You can also help us by supporting our sponsors. Check out some of the sponsor links that were described at the beginning of the episode. Furthermore, recommending the podcast to people that you know and that you think would benefit from the information would be terrific. As always, I will be continuing to post on Instagram and you can expect another podcast episode out next Monday about the topics that we’ve been discussing this month. Above all, thank you for your interest in science.