Huberman Email Heat Exposure Summary

Heat exposure may offer tremendous benefits. However, it is extremely dangerous to use temperatures that are too hot. Pregnant women and children younger than 16 should not sauna. Start slow by using cooler temperatures that don’t significantly increase heart rate. Hyperthermia and dehydration are possible. Also, for men trying to conceive children, repeated deliberate heat exposure can reduce sperm count. The counts rebound after cessation of sauna/hot bath use, but that can take ~45-60 days. Men wishing to avoid sperm count reductions due to heat may opt to apply a cool or cold pack while in the sauna.

There are many ways to access controlled deliberate exposure to heat, including dry saunas, steam saunas, hot tubs, hot showers, or by simply increasing body temperature by wearing warm layers of clothes during a brief jog. Currently, there is insufficient evidence of infrared saunas having additional effects beyond those of a standard sauna, and more importantly, most infrared saunas do not reach the heat ranges for positive health effects.

Cardiovascular Health

Laukkanen et al. found that through regular use of sauna, participants reduced their risk of cardiovascular events/stroke that led to death. They found that increasing the frequency and length of sauna sessions subsequently decreased the long-term risk of cardiovascular disease. Further, the use of sauna has been studied by other clinical groups and positively correlated with a reduction in “all‑cause mortality”.

Heat will trigger some of the same mechanisms in the brain and body as if you were physically engaged in cardiovascular exercise. While in the sauna, heart rate and blood flow increase, and blood vessels will vasodilate (expand) as your body works to cool down in order to regulate body temperature.

Protocol #1—Sauna for Cardiovascular Health

For cardiovascular health, try the following protocol: Heat the sauna to a temperature in the range of 80-100 ℃; 176-212 ℉. NOTE: Your personal heat tolerance should determine the actual temperature. Try to stay in the sauna anywhere from 5 to 20 minutes per session and repeat the use of the sauna from 2 to 3x per week, or as often as 7x per week. More often does appear to be better with respect to cardiovascular health.

Improved Mood

The body responds to heat with a release of dynorphins and endorphins in the brain; dynorphins at first cause discomfort and agitation but biochemically set the stage for endorphins to have enhanced effects on our mood and body, which is why after sauna we feel a mild, happy euphoria.

Improved Stress Response & Overall Health

Studies have found that the regular use of sauna can decrease cortisol levels; enhance the activation of DNA repair/longevity pathways; and increase the activation of Heat Shock Proteins, which help monitor and possibly repair protein structure within our cells. 

Protocol #2—Sauna for General Health

In order to gain the benefits of deliberate heat exposure for general health, including improved mood, stress management, and the enhancement of the body’s hormetic (mild stress) response pathways, use sauna for a total of 1 hour per week, but not all at once. Rather, split that into 2 to 3 sessions. (The sauna temperature should be between 80-100 ℃; 176-212 ℉).

Growth Hormone

Growth Hormone plays a key role in stimulating muscle growth, strengthening bones, repairing tissue, and increasing metabolism. It is released at night while we sleep. Unfortunately, as we age, there is a decline in the amount of natural Growth Hormone. Occasional use of specific sauna protocols, however, has been shown to dramatically boost the amount of Growth Hormone released (up to 16-fold in one study!).

Protocol #3—Sauna for Growth Hormone Release

To use sauna for improved release of Growth Hormone, use the sauna infrequently (once per week or less). However, those days you do sauna, you will be in the sauna for multiple sessions of 30 minutes each with cool down periods in between. GH protocol: 30 minutes in sauna, then cool off outside sauna for 5 minutes, then 30 minutes more in sauna, then cool off. A few hours (or more) later in the day, you repeat that for a total of four 30-minute sessions of sauna in one day.

In order to get maximum Growth Hormone release, use the sauna in a semi-fasted state (having not ingested food for 2 to 3 hours prior). Lower blood glucose levels encourage Growth Hormone release—this is also true for daily Growth Hormone release during sleep. This protocol works best if only used once every week or so. More frequent sauna has other effects but will blunt the Growth Hormone-increasing effects.

To further increase metabolic gains, alternate periods of sauna with deliberate cold exposure during the rest periods. 

Protocol—Other Tips

Hydrate well before and after you use the sauna. Sweat is made of water and other important electrolytes. Drink at least 16 ounces of water for every 10 minutes you spend in the sauna.

Throughout the day, body temperature fluctuates in sync with your natural circadian rhythm. Using the sauna during the afternoon/evening will help match your body’s natural cooling with the “post-cooling sauna effect” in order to aid in falling asleep at night.