Essentials: Using Science to Optimize Sleep, Learning & Metabolism

Introduction to Huberman Lab Essentials (0s)

• Huberman Lab Essentials is a series where past episodes are revisited to provide the most potent and actionable science-based tools for mental health, physical health, and performance (0s).
• The series is hosted by Andrew Huberman, a professor of neurobiology and ophthalmology at Stanford School of Medicine (12s).
• This particular episode is the third episode of the podcast and is titled "Office Hours" (17s).
• The concept of "Office Hours" is based on the traditional practice of students visiting their professor's office to ask questions, seek clarification on confusing topics, or explore a subject in more depth and detail (22s).

Understanding Circadian Rhythms & Light (37s)

• Moonlight, candlelight, and fireplace light do not reset the circadian clock at night and trick the brain into thinking it's morning, despite appearing bright (59s).
• The melanopsin ganglion cells, also known as intrinsically photosensitive ganglion cells, in the eye adjust their sensitivity across the day and respond best to the blue-yellow contrast present in the rising and setting sun (1m22s).
• These cells adjust their sensitivity so they will not activate the triggers in the brain that convey daytime signals when viewing moonlight, even a full moon, or fire (1m47s).
• It is crucial to avoid bright lights between the hours of about 10:00 PM and 4:00 AM, except when necessary for safety or work (2m6s).
• Viewing moonlight at night is okay and will not wake a person up, as the melanopsin ganglion cells do not respond to it in the same way as daytime light (49s).
• Using candlelight or having a fire in the fireplace at night will not be too much light and will not disrupt the circadian clock (53s).

Impact of Red Light on Circadian Rhythms (2m17s)

• Red light, in principle, does not stimulate the melanopsin retinal neurons that wake up the brain and circadian clock, signaling daytime (2m20s).
• However, most commercial red lights are too bright and can wake up the body and brain, despite being marketed for health benefits (2m40s).
• To avoid the negative effects of light later in the day and at night, red light should be very dim, much dimmer than most commercial products (2m51s).
• Dim red lights can be convenient as they allow for visibility without waking up the circadian clock or disrupting dopamine (3m3s).
• Red lights are not necessary, but if used, they should be dim to avoid negative effects on the circadian clock and dopamine (3m9s).

Light Through Windows & Circadian Clocks (3m12s)

• Setting your circadian clock with sunlight coming through a window takes 50 to 100 times longer compared to direct sunlight exposure (3m19s).
• A free app called Light Meter can be used to measure the amount of lux in an environment by taking a picture, and experiments can be done to compare the lux levels outside and through a window (3m22s).
• The amount of lux measured through a window is at least half the amount measured outside, and it does not scale linearly, meaning that the duration of sunlight exposure cannot be directly adjusted based on the lux level (3m36s).
• The best way to set your circadian clock is to get outside in direct sunlight, and if that's not possible, the next best option is to keep the window open (4m10s).
• Wearing prescription lenses and contacts is fine, as they are designed to focus light onto the neural retina, which is different from looking through a window (4m32s).
• The central circadian clocks are looking for a lot of light early in the day, and understanding this can empower individuals to change their behavior in terms of light viewing and other lifestyle factors (4m59s).

Seasonal Changes & Circadian Rhythms (5m5s)

• The Earth spins once every 24 hours on its axis, resulting in periods of sunlight and darkness, and it also travels around the sun in 365 days, which affects day length throughout the year (5m8s).
• The Earth's tilt on its axis causes variations in day length, with days being longer or shorter depending on the time of year and hemisphere, and those near the equator experiencing less variation (5m31s).
• People closer to the poles experience more extreme variations in day length, with very long days and very short days, depending on the time of year and pole location (5m57s).
• Every cell in the body adjusts its biology according to day length, but it only knows night length, and this is determined by the duration of the melatonin signal (6m12s).
• Light inhibits melatonin production, so longer days result in reduced melatonin, while shorter days result in a longer melatonin signal (6m28s).
• The duration of the melatonin signal allows cells to know external day length and time of year, and understanding this can empower individuals to make adjustments to improve their mood and functioning (6m45s).
• Melatonin is associated with reduced functioning of activity-driving and mood-elevating signals, and having control over melatonin through light exposure can help individuals make adjustments to feel better (6m57s).
• It is essential to consider both light exposure and sleep when trying to improve mood, as sleep is necessary for restoring mood, and crushing melatonin production can disrupt sleep (7m24s).

Neurotransmitters & Mood Regulation (7m36s)

• Melatonin is synthesized from serotonin, a neurotransmitter associated with feelings of well-being, calmness, and quiescence, particularly when proper levels are present and an individual feels they have sufficient resources in their immediate environment (7m36s).
• Serotonin is linked to feelings of well-being that come from experiences such as having a good meal, socializing with friends or loved ones, or engaging in meaningful conversations, and it tends to stimulate stillness rather than action (7m43s).
• Dopamine, on the other hand, is a reward neuromodulator that stimulates action and is the precursor to epinephrine, also known as adrenaline, which puts individuals into action (8m18s).
• Epinephrine and adrenaline are essentially the same molecule, with the primary difference being that epinephrine is released within the brain, while adrenaline is secreted from the adrenal glands (9m37s).
• Exposure to light, particularly in the middle of the night, can reduce dopamine levels, potentially causing problems with learning, memory, and mood, making it essential to avoid bright light during this time (8m46s).
• Neuromodulators such as serotonin, dopamine, and epinephrine play a crucial role in modulating brain circuits and influencing various bodily functions, including sleep, wakefulness, and mood regulation (9m2s).
• High amounts of epinephrine released in the brain and body can lead to feelings of stress and agitation, stimulating the desire to move (9m21s).

Exercise & Circadian Rhythms (9m49s)

• There are two primary forms of exercise: cardiovascular exercise, which involves repeating a movement continuously, such as running, biking, or rowing, and resistance exercise, which involves lifting progressively heavier weights that cannot be done continuously for 30 minutes (9m57s).
• While some sources suggest that aerobic exercise is best done in the morning and weight training is best done in the afternoon, there is significant individual variation, and optimal exercise timing may depend on the individual's circadian rhythms (10m28s).
• Research suggests that exercise performance is optimized, and injury is reduced, during specific windows related to body temperature, including 30 minutes after waking, three hours after waking, and the later afternoon, usually 11 hours after waking (10m37s).
• Exercising first thing in the morning can help develop an anticipatory circuit, leading the body to want to wake up at the same time the following days, but it is still important to get light exposure to enhance the wake-up signal to the brain and body (11m8s).
• Combining light exposure and exercise can provide an even bigger wake-up signal to the brain and body (11m30s).
• Some people may experience trouble sleeping if they exercise late in the day, particularly with intense exercise, whereas lower-intensity exercise may not have the same effect (11m41s).

Non-Sleep Deep Rest (NSDR) & Learning (11m52s)

• Neuroplasticity is the brain and nervous system's ability to change in response to experience, and it applies to deep biological mechanisms around wakefulness, time of waking, sleep, and other schedules (11m52s).
• Eating on a tight schedule can lead to anticipatory circuits, where the body starts to feel hungry and agitated before meal times due to peptide signals like hypocretin orexin (12m18s).
• Over time, neurons and neural circuits controlling hypocretin orexin get tuned to the neural circuits involved in eating, smell, and taste, creating a unique eating circuit (13m10s).
• The same principle applies to waking, exercise, and other schedules, including ultradian schedules, where the body starts to anticipate and secrete hormones to prepare for the activity (13m28s).
• Neuroplasticity allows the body to adapt to patterns or rhythms, making it easier to wake up early or exercise at a particular time (13m52s).
• There are two forms of plasticity: one that can be accessed in sleep to improve learning and retention, and Non-Sleep Deep Rest (NSDR) that can be done without sleeping (14m16s).
• Studies on learning in sleep, published in the journal Science, involve individuals performing a spatial memory task and then being tested on their recall after a period of sleep (14m42s).
• These studies have been referenced in Matt Walker's book Why We Sleep and demonstrate the importance of sleep in consolidating memories and improving learning (14m53s).
• A study found that providing the same stimulus, such as an odor or tone, during learning and sleep significantly improved rates of learning and retention of information, suggesting that the subconscious brain can be cued to learn particular things better and faster (16m32s).
• This concept can be implemented by playing a metronome or particular music in the background while learning and then having it faintly play while sleeping, as long as the stimulus is safe and doesn't wake the person up (17m16s).
• Non-Sleep Deep Rest (NSDR) and short 20-minute naps have been shown to increase rates of learning when done for 20-minute bouts, which can match an approximately 90-minute bout of learning (17m55s).
• 90-minute cycles, also known as ultradian cycles, are periods of time during which people tend to learn well, with focused learning feeling like agitation and strain, and then becoming hard to maintain focus and learn more information by the end of the cycle (18m12s).
• A study published in Cell Reports found that 20-minute naps or light sleep of NSDR taken immediately after or close to learning can accelerate learning to a significant degree, both in terms of the amount of information and the retention of that information (18m38s).
• Introducing 20-minute bouts of NSDR can be a cost-free and drug-free way of accelerating learning without having to get more sleep (19m18s).

Nootropics & Cognitive Enhancement (19m23s)

• The ultradian learning cycle involves 20 minutes of focused learning followed by a 90-minute break, which can be beneficial for learning and plasticity (19m24s).
• Nootropics, also known as smart drugs, are substances that aim to enhance cognitive function, particularly focus and learning (19m33s).
• Effective learning requires the ability to focus and block out distractions, which triggers the acetylcholine neuromodulator, allowing for synaptic changes during sleep (19m50s).
• No nootropic can bypass the need for sleep and deep rest, which is essential for learning and memory consolidation (20m17s).
• Most nootropics combine multiple ingredients, including stimulants like caffeine, which can increase alertness but may not lead to sustained focus (20m27s).
• Many nootropics also include ingredients that increase acetylcholine, such as Alpha-GPC, which can enhance focus and learning (20m38s).
• A balanced nootropic should include components that promote focus, alertness, and an "off switch" to prevent crashes and promote restful sleep (20m48s).
• The ideal nootropic would stimulate alertness through epinephrine and acetylcholine through choline donors or Alpha-GPC, while also allowing for restful sleep (20m55s).
• The current stance on nootropics is that they may be useful for occasional use, provided they are safe, but may not be effective for long-term learning and memory due to their shotgun approach (21m33s).

Temperature & Circadian Rhythms (21m55s)

• Body temperature tends to be lowest around 4:00 AM and starts increasing around 6:00 AM, peaking between 4:00 PM and 6:00 PM, with temperature also linked to day length, being hotter during longer days and colder during shorter days (22m17s).
• A regular circadian rhythm is linked to a regular body temperature rhythm, which affects metabolism and the willingness to exercise, typically peaking 30 minutes after waking, three hours after waking, and 11 hours after waking (23m4s).
• The willingness to exercise and engage in activities is highest when body temperature is rising, with the steepest slope of the temperature line (23m22s).
• Temperature and circadian rhythm are linked through the suprachiasmatic nucleus, the master circadian clock, which informs cells and tissues of the body and synchronizes their temperature (23m53s).
• The master circadian clock puts cells into a cohesive rhythm by secreting a peptide and synchronizing the temperature under which those cells exist, making temperature the effector of the circadian rhythm (24m17s).
• Cold showers and ice baths can cause a rebound increase in thermogenesis, shifting the circadian rhythm depending on the time of day, with late-day increases making the day longer and phase delaying the clock (24m30s).
• Increasing body temperature after 8:00 PM, whether through ice baths or exercise, can extend the day, shift the clock forward, and give the perception that the day is getting longer, making it harder to wake up in the morning (25m1s).
• Taking a cold shower in the morning can wake a person up in the short term and also shift their circadian rhythm, making them more likely to wake up earlier the next day, by about half an hour to an hour earlier than usual (25m36s).
• Taking a cold shower while body temperature is falling can delay wake-up time and make the body perceive the day as longer (25m57s).
• Temperature is the effector that impacts all cells and tissues in the body, with the central circadian clock influencing these changes, while light is the trigger and the suprachiasmatic nucleus is the master circadian clock (26m10s).
• Non-photic influences, such as exercise and feeding, can also impact the circadian rhythm (26m25s).
• Eating can also be used to shift the circadian rhythm, as getting on to the local meal schedule when traveling can help adjust to a new time zone more quickly (26m35s).
• The effect of eating on the circadian rhythm may be due to changes in body temperature and eating-induced increases in body temperature, as well as the anticipatory secretion of hypocretin orexin (26m50s).

Food, Neurotransmitters & Circadian Rhythms (27m4s)

• The relationship between food, neurotransmitters, and circadian rhythms is complex, with certain foods influencing neuromodulator levels, such as tyrosine-rich foods like nuts and red meats, which can increase dopamine and epinephrine production, associated with wakefulness (27m57s).
• The volume of food consumed also affects wakefulness, as a large amount of food can divert blood to the gut, leading to sleepiness, regardless of the food's content (28m25s).
• Fasting states are generally associated with increased alertness, epinephrine, and wakefulness, while fed states are associated with relaxation, serotonin, and sleepiness (28m44s).
• Eating has effects on circadian rhythm and wakefulness, independent of the food itself, such as eating-induced thermogenesis, which can shift the body's rhythm earlier or later, depending on the timing of meals (29m29s).
• Eating early in the day can lead to an earlier wake-up time the next day, while eating late in the day can lead to a later wake-up time, even if sleep is achieved (29m39s).
• Tryptophan, a precursor to serotonin, is obtained from the diet, and its levels can be influenced by food consumption (27m27s).
• The precursors to neurotransmitters, such as tyrosine for dopamine and tryptophan for serotonin, are circulated to various cells and tissues after ingestion (27m40s).
• The foods we eat can influence neuromodulator levels to some extent, with certain foods lending themselves to the production of specific neurotransmitters (27m52s).

Self-Experimentation & Conclusion (29m52s)

• To gain a better understanding of one's physiology, it is suggested to keep a daily log of activities such as going outside for sunlight, exercising, feeling chilled or hot, and practicing Non-Sleep Deep Rest (NSDR) protocols, in relation to waking times (29m55s).
• By tracking these patterns, individuals can identify correlations between their behaviors and sleep, attention, and wakefulness, allowing them to make informed adjustments (30m39s).
• Self-experimentation can help reveal the effectiveness of different techniques, such as cold exposure or sauna use, at various times of the day (30m59s).
• It is essential to note that using cold exposure or sauna late in the day may have different effects than using them early in the day, and individuals should experiment to find what works best for them (31m4s).
• Some people may experience a compensatory decrease in body temperature after using a sauna or hot tub, which can aid in sleep, but hydration is crucial in these cases (31m15s).
• Engaging in sauna or hot tub activities early in the day can lead to a temperature drop, which may interfere with the body's natural temperature regulation and circadian clock entrainment (31m39s).
• Becoming a "scientist of one's own physiology" involves experimenting with different tools and techniques to understand their effects on sleep, attention, and wakefulness patterns (31m45s).
• Self-experimentation should be done slowly and carefully, manipulating one or two variables at a time to identify the most powerful factors influencing one's body and mind (32m21s).
• The goal of self-experimentation is not to adhere to a rigid schedule but to identify and adjust variables that push the body and mind in desired directions (32m5s).