Thank you for joining the Huberman Lab Podcast Neural Network—a once-a-month newsletter with science and science-related tools for everyday life. The purpose of this newsletter is to provide you with actionable information in condensed form.
In many episodes and guest interviews, I have discussed the benefits of deliberate heat exposure for overall health, improved mood, adjusted hormone levels, and athletic performance and recovery. Episode 69 was a deep dive into the scientific literature about what the specific mechanisms are by which heat can positively impact the body and brain. I also outlined specific protocols aimed at providing specific goal outcomes. Below, I detail the key takeaways from that episode and outline three protocols that use deliberate heat exposure as a powerful means to improve health, mood, and longevity.
When done correctly, heat exposure offers tremendous benefits. However, it is extremely dangerous to use temperatures that are too hot. What is too hot? That will depend, but in general, pregnant women and children younger than 16 should not sauna. Start slow—using cooler temperatures that don’t significantly increase heart rate. Hyperthermia (abnormally high body temperature) and dehydration are always possible, so proceed with caution. Also, for men trying to conceive children, please know that 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; this is not possible in a hot bath/tub, for obvious reasons.
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. Pick whatever method or methods you can routinely work into your schedule and that match your budget. Note: Recently, the use of infrared saunas has become popular. Currently, there is insufficient evidence of their having additional effects beyond those of a standard sauna, and more importantly, most infrared saunas do not reach the heat ranges outlined below for positive health effects.
Regular use of sauna can improve cardiovascular health. Laukkanen et al. found that through regular use of sauna, participants reduced their risk of cardiovascular events/stroke that led to death. This paper 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”—a catchall term referring to death from any cause.
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
In order to use sauna to benefit 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.
Saunas have traditional roots in Scandinavian cultures. For centuries, many who regularly use sauna have noticed a correlation between their sauna use and 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
Hormesis is mild, tolerable stress that stimulates the body and helps it to positively adapt. Hormesis can take many forms, and heat is one such form. 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 unique heat-dependent molecular mechanisms, termed Heat Shock Proteins, which help monitor and possibly repair protein structure within our cells. The integrity of protein structures is vital to our health and wellbeing.
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 plays a key role in stimulating muscle growth, strengthening bones, repairing tissue, and increasing metabolism. (Learn more about Growth Hormone in this episode of the Huberman Lab Podcast). Growth Hormone 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. Peer-reviewed research says this protocol works well to increase growth hormone: 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 (that’s a lot!)
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. (Listen for more tips to encourage daily Growth Hormone release.) Again, 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. Read more about specific protocols for cold exposure.
Remember to 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.