Main Takeaways From Huberman Lab Podcast on Heat & Sauna
Key insights: 60-second read
- Regular sauna use (2-7 times weekly) reduces cardiovascular mortality - 4-7 sessions weekly linked to 50% lower risk of fatal cardiovascular events compared to once weekly.
- Optimal protocol: 80-100°C (176-212°F) for 5-20 minutes per session - this temperature range and duration appears most effective for health benefits.
- Heat exposure activates protective mechanisms - including heat shock proteins, FOXO3 (DNA repair), and endorphin pathways.
- For growth hormone release: less frequent, longer sessions - 30-minute sessions repeated 4 times in one day, done only once weekly, produced 16-fold increases in growth hormone.
- Mood benefits come through discomfort - dynorphin release during uncomfortable heat exposure upregulates feel-good endorphin systems, improving baseline mood.
Heat is a remarkable biological stimulus. When we expose ourselves to a hot environment, it triggers profound changes throughout our body and brain. From reducing cardiovascular risk to enhancing mood and potentially extending lifespan, deliberate heat exposure is one of the most potent and accessible health tools available.
In this episode of the Huberman Lab Essentials podcast, Dr Andrew Huberman, professor of neurobiology and ophthalmology at Stanford School of Medicine, breaks down the science of heat exposure. He explains the neural circuits that control body temperature, reviews the clinical evidence for sauna use, and provides specific, evidence-based protocols for achieving different health outcomes.
This article summarises the key findings and actionable tools from that discussion, with a focus on practical applications for physiotherapy patients and health-conscious individuals.
"When you understand how your shell and core temperatures work, you can design protocols that are literally perfect for your goals."
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Shell vs core temperature: a critical distinction
Throughout your entire lifespan, your body maintains two distinct temperatures. The first is your shell temperature, the temperature of your skin. The second is your core temperature, the temperature of your viscera (organs), nervous system, and spinal cord.
Your brain constantly sends signals to your body about whether to heat up or cool down based on the temperature of your shell. Understanding this distinction is fundamental to designing effective deliberate heat exposure protocols.
Important safety note: Unlike cold exposure, where you have a fairly broad range before tissue damage occurs, overheating the brain and body carries significant risk. Neurons in the central nervous system, once damaged, do not regenerate. Hyperthermia is a serious condition to avoid. Always stay within safe temperature ranges and listen to your body.
The body's heat regulation circuit
Neurons in your skin contain specialised channels called TRP channels that sense changes in heat. These neurons send electrical signals to your spinal cord, specifically to a cluster of neurons in the dorsal horn. From there, signals travel to the lateral parabrachial area (a relay station) and then to the preoptic area (POA) of the hypothalamus, which sits just above the roof of your mouth.
The POA is the master regulator. It sends signals throughout your brain and body to initiate heating or cooling responses. These include:
- Autonomic responses: Sweating (below conscious control) and vasodilation (widening of blood vessels to release heat)
- Behavioural responses: Lethargy on hot days and the agitation that makes you want to move out of a hot environment (mediated by the POA communicating with the amygdala and adrenal glands to release adrenaline)
Cardiovascular benefits and mortality reduction
A landmark 2018 prospective cohort study published in BMC Medicine examined the relationship between sauna bathing and cardiovascular mortality in 1,688 participants (mean age 63, 51.4% women). The findings were striking:
- People who used the sauna 2-3 times per week were 27% less likely to die of a cardiovascular event compared to those who used it once weekly
- People who used the sauna 4-7 times per week were 50% less likely to die of a cardiovascular event compared to once-weekly users
The researchers controlled for potential confounding variables including smoking, body weight, and exercise habits, confirming that the benefits were specifically attributable to sauna exposure rather than correlated lifestyle factors. Subsequent analyses have also found reductions in all-cause mortality (death from any cause).
"People who went into the sauna 4 to 7 times per week were 50% less likely to die of a cardiovascular event compared to people that went into the sauna just once a week."
Sauna protocols: temperature, duration, frequency
Based on the studies reviewed, the effective temperature range for deliberate heat exposure is 80-100°C (176-212°F). Session duration typically ranges from 5 to 20 minutes.
For cardiovascular and longevity benefits, the evidence supports 2-7 sessions per week, with greater frequency associated with greater risk reduction.
Core protocol for general health
Temperature: 80-100°C (176-212°F)
Duration: 10-20 minutes per session
Frequency: 2-7 times per week
Expected benefits: Reduced cardiovascular mortality, improved metabolic health, enhanced stress resilience
Alternatives to sauna
You do not need a traditional sauna to access these benefits. The key is safely heating your shell and core temperature. Alternatives include:
- Steam saunas and infrared saunas
- Hot tubs or hot water immersion (up to the neck)
- Hot rooms (crank up the heat in a small room)
- Exercise in warm clothing (hoodie, wool hat, or plastic sweat suits used by wrestlers) on a hot day
Huberman notes that sauna is simply the most convenient and controlled method for research purposes. There is nothing special about sauna itself; the biological effects come from elevating core and shell temperature regardless of method.
Cortisol reduction and stress management
A 2021 study examined the endocrine effects of repeated hot thermal stress and cold water immersion in young adult men. The protocol involved four sauna sessions of 12 minutes each at 90-91°C (194°F), followed by a 6-minute cool-down break in 10°C (50°F) water.
The major finding was a significant decrease in cortisol output. For individuals dealing with chronic stress, elevated cortisol, or low stress resilience, this protocol offers a research-backed approach to reducing cortisol levels. The practical application could be sauna followed by a cool shower, even if not as extreme as the study conditions.
Heat shock proteins and FOXO3: cellular protection
Heat shock proteins (HSPs) are protective mechanisms in your brain and body that rescue proteins from misfolding due to heat stress. When your body temperature increases, HSPs deploy to prevent detrimental protein changes.
One particularly important pathway involves a molecule called FOXO3, which sits upstream of DNA repair pathways and clearance of senescent (aged or damaged) cells. Regular sauna exposure (2-7 times weekly in the 80-100°C range) has been shown to upregulate FOXO3 activity. Individuals with hyperactive versions of FOXO3 or additional copies of the FOXO3 gene are 2.7 times more likely to live to 100 years or longer.
Deliberate heat exposure is one way to increase FOXO3 activity, potentially supporting DNA repair and cellular health.
Growth hormone: the 16-fold increase protocol
A 1986 study (still foundational in this field) examined the effects of repeated sauna bathing on growth hormone. The protocol was intense: subjects spent 30 minutes in an 80°C (176°F) sauna, followed by a cool-down rest, repeated four times in a single day (2 hours total). This was done on days 1, 3, and 7 of a week.
The results showed a 16-fold increase in growth hormone on day 1. However, the effect diminished with repeated exposure: on day 3, the increase was roughly 3-4 fold; on day 7, approximately 2-3 fold.
This diminishing effect reflects heat adaptation. Just as running up a hill becomes easier with repeated practice, your body becomes more efficient at thermoregulation, reducing the hormonal shock response.
Protocol for growth hormone release
Frequency: No more than once weekly (or once every 10 days)
Session structure: 30 minutes in sauna (80°C/176°F), cool-down rest, repeat for a total of 4 sessions (2 hours total heat exposure)
Timing: Evening, ideally fasted (no food for 2-3 hours before)
Expected benefit: Large, acute increase in growth hormone (diminishes with adaptation)
Caveat: If you become heat adapted, you will not get the same magnitude of growth hormone increase
Timing, sleep and hydration
For most people, the best time to use deliberate heat exposure is later in the day or evening. When you enter a hot environment, your shell and core heat up, but this activates cooling mechanisms through the preoptic area. After you exit, your body continues to cool down, which many people find helps them fall asleep.
This cooling effect is the opposite of cold exposure, which can make it harder to sleep for some people due to post-exposure body temperature increases.
Hydration is critical. A reasonable guideline is to drink at least 16 ounces (approximately 470 mL) of water for every 10 minutes in the sauna. Electrolyte replacement may also be necessary depending on how much you sweat and your individual salt excretion patterns.
Mood, endorphins and dynorphin
Deliberate heat exposure improves mood through a counterintuitive mechanism involving two types of opioid peptides.
Endorphins bind to mu-opioid receptors and produce pain relief and mild euphoria. Dynorphin binds to kappa-opioid receptors and produces agitation, stress, and pain. When you enter an uncomfortably hot environment, your body releases dynorphin. This is part of why you want to get out.
However, dynorphin binding to kappa receptors triggers a compensatory upregulation of mu-opioid receptors (the feel-good endorphin system). Over time, this makes the feel-good system much more efficient. People experience an elevated baseline mood and heightened pleasure in response to positive events.
"A little bit of discomfort as a consequence of deliberate heat exposure... is activating pathways that are allowing the feel-good molecules and neural circuitries that exist in your brain and body to increase their efficiency, placing you in a better position to be joyful in response to the events of life."
Protocol recap by goal
| Goal | Temperature | Duration | Frequency | Special considerations |
|---|---|---|---|---|
| Cardiovascular health / Longevity | 80-100°C (176-212°F) | 10-20 minutes | 2-7 times per week | More frequent = greater benefit |
| Growth hormone release | 80°C (176°F) | 4 x 30 minutes (with cool-down breaks) | Once weekly or less | Evening, fasted, avoid adaptation |
| Cortisol reduction / Stress | 90-100°C (194-212°F) | 12 minutes | As tolerated | Follow with cool water immersion or cool shower |
| Mood / Mental health | Comfortably uncomfortable range | 5-20 minutes | Regular (2-7 times per week) | Discomfort is the mechanism; safety first |
| Heat shock proteins / FOXO3 | 80-100°C (176-212°F) | 10-20 minutes | 2-7 times per week | Upregulates cellular repair pathways |
Key insight: The same sauna protocol (2-7 times weekly, 10-20 minutes, 80-100°C) supports cardiovascular health, mental health, and cellular repair mechanisms. The growth hormone protocol is an exception requiring less frequent, more intense exposure. Most people will benefit most from regular, moderate-frequency sauna use.
Video transcript with timestamps (click to jump)
One key insight from this episode
"Regular sauna use (4-7 times per week at 80-100°C for 10-20 minutes) is associated with a 50% reduction in cardiovascular mortality compared to once-weekly use. The benefits extend to all-cause mortality, stress reduction (via cortisol decrease), and mood enhancement through dynorphin-mediated upregulation of endorphin systems."
Frequently asked questions
Is sauna safe for people with high blood pressure or heart conditions?
This is an important question that requires individualised medical advice. While the studies discussed show cardiovascular benefits in general populations, sauna use does increase heart rate and blood flow. Individuals with known cardiovascular disease, uncontrolled hypertension, or other heart conditions should consult their doctor before starting any deliberate heat exposure protocol. The same caution applies to pregnant women and individuals taking medications that affect blood pressure or thermoregulation.
Can I combine sauna with exercise on the same day?
Yes, many people do. However, be mindful of hydration status and total physiological load. If you are doing intense exercise, your body is already generating significant internal heat. Adding sauna immediately after may increase risk of overheating. A common approach is to exercise, allow your body to cool down (10-20 minutes), hydrate, then use the sauna. Alternatively, some people prefer sauna on rest days to separate the stressors. Listen to your body.
How do I know if I am becoming heat adapted?
Heat adaptation manifests as more efficient sweating (starting sooner, producing more sweat), lower heart rate during heat exposure, reduced perception of discomfort, and blunted hormonal responses (including smaller growth hormone spikes). Adaptation is not inherently bad; for cardiovascular and longevity benefits, adaptation is part of how regular sauna use produces its effects. However, if your goal is large growth hormone spikes, adaptation will reduce that specific response.
What if I cannot tolerate 80°C?
Start lower. The studies used specific temperature ranges, but individual tolerance varies significantly based on heat adaptation, body composition, genetics, and other factors. Start at a temperature that is comfortably uncomfortable (you want to get out, but it is safe to stay). Over time, as you become heat adapted, you will likely tolerate higher temperatures. The key is consistency and safety, not hitting a specific number.
Can children use sauna?
The studies discussed focused on adult populations. Children have different thermoregulatory capacity and lower body mass to surface area ratios, which affects how quickly they heat up. If considering sauna for children, medical guidance is recommended. Generally, lower temperatures and shorter durations would be appropriate, with direct supervision.
As a physiotherapist, I often discuss recovery, stress management, and lifestyle factors with my patients. The evidence for deliberate heat exposure is compelling, particularly for cardiovascular health, stress reduction, and recovery from physical activity.
However, like any therapeutic tool, sauna use must be individualised. A patient with uncontrolled hypertension, a recent heart attack, or certain medications may not be a candidate. Always consult your doctor before starting any new heat exposure protocol, especially if you have pre-existing medical conditions.
If you are looking for ways to enhance recovery, manage stress, or improve your overall health profile, I am happy to discuss how tools like deliberate heat exposure might fit into your broader physiotherapy and wellness plan. I see patients in Port Macquarie and via telehealth.
- Grant
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Disclaimer: This information is for educational purposes and does not replace individualised medical advice. Always consult a qualified health professional before starting any new health protocol, including deliberate heat exposure. This article summarises the Huberman Lab podcast episode on heat exposure; the original source should be consulted for full context. Individual responses to heat exposure vary significantly.
1 comment
Interesting information. I’m curious, are the effective temperature ranges the same for infrared and traditional saunas?