Benefits of Sauna & Deliberate Heat Exposure | Huberman Lab Essentials
In a Nutshell
Deliberate heat exposure via sauna (80-100°C, 5-20 min/session) reduces cardiovascular mortality by up to 50% with 4-7 sessions/week, lowers cortisol, boosts heat shock proteins and FOXO3 for longevity, and enhances mood by upregulating endorphin pathways through dynorphin release. For maximum 16-fold growth hormone spikes, limit to rare intense protocols (e.g., 4x30 min once weekly); regular use adapts and diminishes this effect. Hydrate with electrolytes post-session, time evening for sleep benefits via post-heat cooling, and start conservatively to avoid hyperthermia.
These notes were generated by AI and may contain inaccuracies.
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. Andrew Huberman is a professor of neurobiology and ophthalmology at Stanford School of Medicine. Today we are talking about the science of heat. Heat is a remarkable stimulus, meaning when we are in a hot environment, it has a profound effect on our biology. We're going to talk about the science of heat and heating both in terms of their mechanisms and tools related to the use of heat things like sauna, how often to do sauna, how long to be in the sauna, how hot to be in the sauna for particular goals and outcomes.
Heat up two ways: from the outside, meaning the things that we come into contact with, the clothing that we put on our body, whether or not there's heat in the room or whether or not it's cold outside or cold in a room. And we heat up from the inside. At every point across your entire lifespan, you have two distinct temperatures. One is the temperature on your skin, what scientists call your shell, and the temperature of your core, your viscera, meaning your organs, your nervous system, and your spinal cord. It is vitally important to understand that you have those two temperatures, and that your brain is constantly sending out signals to your body as to whether or not it should heat up or cool down depending on the temperature of the shell.
Anytime we're talking about heat, meaning deliberate heat exposure, things like sauna, it's very important to understand not just the stimulus, how hot something is, how long you're in a sauna, etc., but the effect that has on your shell and on your core. If you can understand that, you can design protocols that are literally perfect for your goals.
Warning: Anytime you're talking about heating up your body, you need to be very cautious because unlike cooling down where you have a fairly broad range of cold temperatures that you can go into before it's damaging to tissue, you don't get to heat up the brain and body very much before you start getting into the realm of neuron damage. And neurons in the central nervous system, the brain and spinal cord, once they're damaged, they don't come back. So, hyperthermia is a serious thing to avoid.
There's a very basic circuit, meaning neurons that exist in the skin, in the brain, and in the body that communicate with one another that allow you to heat up if you need to and cool down if you need to.
Circuit Structure
- Skin: Neurons with TRP channels (and others) sense changes in heat. If a hot object is placed on your hand or arm and removed, those neurons send electrical signals into your spinal cord.
- Spinal cord: Cluster of neurons at the top part called the dorsal horn relay heat information up to the brain.
- Lateral parabrachial area: Relay station that sends signals to the POA (preoptic area).
- Preoptic area (POA): Neurons in the hypothalamus, residing over the roof of your mouth, send signals out to the rest of your brain and body to heat up and change your behavior.
Mechanisms to dump heat:
- Physiological (autonomic): Sweating, vasodilation (dilation of veins and capillaries).
- Behavioral: Lethargy on hot days, impulse to leave hot environment (POA communicates with amygdala, activating adrenal glands above kidneys to release adrenaline, creating agitation to move).
Now you know the circuit: skin to spinal cord, one brain area to another brain area (key one: POA). If you can conceptualize that circuit, you're in a great position to understand the rest of the information and tools.
The use of deliberate heat exposure can be a very powerful way to improve health and longevity.
Key Study (2018)
- Title: Sauna bathing is associated with reduced cardiovascular mortality and improves risk prediction in men and women, a prospective cohort study (published in BMC Medicine).
- Sample: 1,688 participants, mean age 63 (range around 63), 51.4% women.
- Compared sauna use: once vs. 2-3 times/week vs. 4-7 times/week.
- Findings:
- 2-3 times/week: 27% less likely to die of cardiovascular event than once/week.
- 4-7 times/week: 50% less likely to die of cardiovascular event than once/week.
- Controlled for confounders: smoking, overweight, exercise.
- Reduces cardiovascular mortality, stroke, all-cause mortality (e.g., cancer).
Sauna parameters (unless specified otherwise): 80°C (176°F) to 100°C (212°F), 5-20 minutes per session.
Alternatives to sauna: Heat shell and core properly (not too much, not too little). Options:
- Dry saunas, steam saunas, infrared saunas, hot tubs, hot baths to neck.
- Wear hoodie/wool hat, jog in heavy clothing, use plastic suits (like wrestlers for water weight loss) on hot day.
- Caution: Hydrate, avoid overheating, heat stroke, hyperthermia.
What happens in hot environment:
- Blood flow increases, plasma volume increases, stroke volume (blood per heart beat) increases.
- Heart rate: 100-150 bpm.
- Mimics cardiovascular exercise (without joint loading, bone density benefits).
Hormone Effects
Study (2021): Endocrine effects of repeated hot thermal stress and cold water immersion in young adult men.
- Protocol: 4 x 12-min sauna sessions at 90-91°C (194°F), with 6-min cooldown in 10°C (50°F) water between.
- Major effect: Significant decrease in cortisol.
- Tool for stress reduction: 12-min heat exposure (90°C) + 6-min cool (50°F shower/water). Alternatives: 12-min jog in heavy clothes on hot day + cool shower.
Heat Shock Proteins (HSPs)
- Activated by heat exposure to rescue misfolding proteins (like cooking changes protein texture/configurations).
- Travel brain/body to prevent detrimental protein changes, protect cells.
- Good short-term; not for long periods.
- Well-established in animal models and humans.
FOXO3 Mechanism
- FOXO3: Involved in DNA repair, clearing senescent cells.
- Sauna 2-3 (ideally 4-7) times/week at 80-100°C upregulates FOXO3.
- FOXO3 hyperactive individuals or with extra copies: 2.7x more likely to live to 100+.
- No protocol targets one mechanism specifically; heat impacts all (cortisol, HSPs, FOXO3).
General protocol guide: 80-100°C, 5-20 min/session, adjust to tolerance (start low, adapt over time, improve sweating).
Growth hormone: Impacts metabolism, cell/tissue growth, repair; drives puberty growth spurt. Declines from early 30s; released nightly in slow-wave sleep (less with age). Useful for recovery, fat loss, muscle growth, injury repair.
Study (1986): Endocrine effects of repeated sauna bathing.
- Protocol: 80°C (176°F), 30 min x 4/day (2 hours total), cooldown rests between; done days 1, 3, 7 of 1-week study; male/female subjects.
- Result: 16-fold increase in growth hormone (measured pre/post-sauna).
- Caveat: Effects diminish with more frequent exposure (less on day 3 vs. day 1, even less on day 7).
On day one of sauna sessions, there was a 16-fold increase in growth hormone. On day three, the effect was still significant but reduced by about two-thirds, resulting in a three- or four-fold increase. By day seven, it was a two- or three-fold increase, less than day one.
This diminution suggests either less efficient temperature signaling or reduced impact due to adaptation of downstream factors, with the latter more likely. This mirrors adaptation in weight training or cardiovascular exercise: running up a hill is initially painful with burning lungs, but repeated sessions with recovery make it easier as the body adapts.
To trigger massive growth hormone increases via deliberate heat exposure, limit to once a week or every 10 days. Frequent sessions lead to heat adaptation, reducing the response. Time sessions with hard workouts, fat loss efforts, or for peak growth hormone, perhaps three to four times per month. More frequent exposure still increases growth hormone, but not as massively as infrequent shocks.
Timing matters for sauna or cold exposure. Cold exposure raises body temperature immediately after, potentially disrupting sleep unless extremely tired. The speaker has done late-evening ice baths or cold showers during busy periods without sleep issues.
For deliberate heat exposure, later in the day is wise: the body's shell and core heat up, activating cooling via the preoptic area. Exiting triggers ongoing cooling, aiding sleep. Many find sauna in the later half of the day or before bed, followed by a warmish shower to rinse sweat, promotes easier sleep due to dropping body temperature.
For maximum growth hormone release, evening or nighttime is best, especially fasted for two hours before sleep. This aligns with growth hormone pulses early in sleep. Protocol: sauna once or twice weekly in evening/night, then warm/cool shower, with low blood glucose/insulin (fasted or no food 2-3 hours prior), as elevated glucose/insulin blunts growth hormone from stimuli like exercise or sauna.
For 90% of people 90% of the time, 1-3 sauna sessions weekly suffice without obsessing over conditions.
Always hydrate post-sauna, as it causes water loss needing replacement for cells and electrolytes. No exact formula; varies by sweat amount (heat adaptation), salt excretion. General rule: drink at least 16 ounces of water per 10 minutes in sauna, before/during/after or after only.
Deliberate heat exposure improves mood, well-being, and capacity to feel good from ordinarily pleasurable things by upregulating brain/body pleasure pathways.
Endorphins are released in response to stressors. Exercise like long runs triggers endorphin release via stress, reducing pain and inducing euphoria.
Endorphins include feel-good types binding mu opioid receptors (pain relief, mild euphoria) and dynorphins (d-y-n-o-r-p-h-i-n) that worsen feelings.
Hot sauna liberates dynorphins from many brain neurons. Discomfort and urge to escape partly stem from dynorphin binding kappa receptors, causing agitation, stress, pain—alongside sympathetic activation and preoptic area to amygdala fight-or-flight.
In safe but uncomfortable heat, dynorphin binds kappa receptors, increasing receptors for feel-good endorphins (e.g., mu opioid). Uncomfortable heat/cold releases dynorphin, enhancing efficiency of feel-good systems over time, elevating baseline mood and amplifying joy/happiness/awe from positive events.
Short-term discomfort activates pathways boosting feel-good molecule efficiency, positioning for greater life joy.
Sauna protocols (5-20 minutes, 1-7 times/week) improve cardiovascular health, mental health. Acute extreme use (3-4x/day, 30 minutes each with cooling) spikes growth hormone; regular use reduces cortisol, improves heart/mental health.
Accessible via sauna, hot bath, bundling for jog. Activates cascades improving brain/body health.
Each protocol activates pathways to varying degrees. Mechanisms allow customizing for needs.
- Max growth hormone: Seldom (≤1x/week or less), multiple sessions/day (e.g., 4x30min once weekly).
- Cardiovascular/longevity: 3-7x/week, 80-100°C.
- Mental health: Uncomfortable but safe heat to release dynorphin, enhancing endorphin effects.
Timing: post-workout (morning/afternoon) or later day for sleep via cooling (1+°C drop aids sleep onset). Exception: if exhausted or great sleeper, anytime.
Thank you for joining the discussion on science of heat for health and interest in science.
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