Over the past 30 years, many studies have come out suggesting that regular sauna use can improve your health. Possible health benefits include increased insulin sensitivity (which can help prevent diabetes), faster recovery from injury, increased longevity, improved muscle development, and even increased neurogenesis, the creation of new brain cells.
Are saunas a health strategy all of us can adopt? If so, what are the best practices we should follow in using them? To get to the bottom of these questions, I went to the real experts on sauna use: the Finnish medical establishment. Then I followed that up with a review of the major studies on the topic.
Through this combination of Q&A and research, I’m hoping you can use this article as a guide to adopting and optimizing your own sauna strategy.
With 3 million saunas for 5 million people, Finland is the world leader in sauna usage. Virtually all gyms in Finland have saunas, as do the vast majority of homes. Even many offices have a sauna.
Over email, I interviewed two of the world’s leading academic experts on the health and hormonal benefits of sauna usage. It’s no surprise that both are located in Finland.
Juhani Leppäluoto is a medical doctor and professor emeritus at the University of Oulu’s Institute of Biomedicine. He has published over 300 research articles, including some of the most-cited articles on the hormonal effects of sauna usage.
Katriina Kukkonen-Harjula is a medical doctor specializing in exercise, sports medicine, community medicine, and public health. She has worked most of her career as a researcher at the UKK Institute for Health Promotion Research in Tampere, Finland, focusing on healthy lifestyles. For the past five years she has worked in geriatric rehabilitation in the South Karelia Hospital District in Lappeenranta, Finland.
What is the ideal sauna temperature?
Kukkonen-Harjula: 80 degrees Celsius (176 Fahrenheit) for relaxation, which also seems to prevent heart attacks and stroke. Based on recent Finnish research data, this [increases] longevity.
Leppäluoto: Recommendations are for a sauna temperature of 80–100 degrees Celsius (176–212 degrees Fahrenheit).
If you’re using a sauna at your gym, you might not be in control of its temperature. Below we cover other ways to adjust the experience.
To optimize the health benefits of the sauna, how long should a sauna session be, and how frequently should people visit it?
Kukkonen-Harjula: Sessions should be around 10–20 minutes and should be repeated a few times after relaxing outside the hot room for 5–10 minutes (showering, swimming, or just sitting) once a week or more often. This is the Finnish tradition, which can also be seen at present in people often having electrically heated sauna rooms in cities and in their own condos.
Leppäluoto: Several sessions of 5 to 20 minutes [should be conducted] lasting up to one to two hours, two to four times weekly. This [recommendation applies to] all healthy subjects.
Many studies and popular articles suggest that users should engage in just one 15-minute session in the sauna, but the Finnish tradition is to do multiple rounds of sauna time, with breaks in between. The sum of the time spent during all sessions might be an hour or longer.
Is there an ideal time of day to take a sauna bath or an ideal time relative to exercise?
Kukkonen-Harjula: Exercise before sauna bathing. Traditionally, sauna bathing took place on Saturday evening, as [the sauna] also was a place to wash oneself. Nowadays you can use the sauna any time you want, but the idea is usually for sauna bathing to relax you.
Leppäluoto: Exercise is not good 6 to 10 hours after using the sauna, but after exercising, athletes go to the sauna to relax their muscles. The more you go to the sauna, the longer you will live.
How significant and long-lasting do you think the testosterone boost from a sauna session is?
Leppäluoto: As far I know, sauna use has only minor effects on plasma testosterone.
Note: One of Leppäluoto’s studies did find that sauna usage increases growth hormone secretion, though only for about 45 minutes, and possibly only in younger (under 50) men.
Kukkonen-Harjula: It’s a stress reaction. The hormonal boost is transient and usually fades away within hours of bathing.
In America, a lot of people believe that using a sauna after lifting weights will help you build more muscle. What do you think about that?
Kukkonen-Harjula: I have not heard about this — but I have not worked with athletes, but rather with ordinary persons to get them moving instead of sitting. Does this belief also affect women? All in all, I do not believe it is true. It should be tested in a laboratory, with randomized groups in a double-blind study, but I do not think it would be worthwhile.
Leppäluoto: Repeated lifts with increasing resistance build muscle power. Weight lifters use the sauna to relax muscles and shorten their recovery time before the next exercise. The sauna is also used to reduce body weight in competitions in which body weights determine classes, such as boxing, wrestling, and weight lifting.
In the last sentence, Leppäluoto is referring to the use of saunas to temporarily lose water weight. Athletes usually refer to this as “cutting weight,” with the idea that they’ll rehydrate after the competition’s weigh-in and before the actual competition. You, the reader, probably don’t have a reason to do this.
Is there any difference between a sauna and a steam room?
Leppäluoto: In a steam room, the humidity is close to 100 percent, and therefore the temperature must be below 40 degrees Celsius (104 degrees Fahrenheit). For athletes, a steam room acts in a way similar to a sauna, [but] it may transfer heat sooner to muscles than a sauna would.
I asked this question for people outside of Finland who don’t have universal access to a sauna. It sounds like a steam room would be an effective replacement for a sauna.
How should I sit in the sauna? Should I opt for a hotter experience by increasing my skin contact with the wood (leaning against the back) or have my head higher where the air seems to be warmer?
Leppäluoto: It is recommended that you sit in the sauna. The walls and benches will be hot, and a towel should be used. If you lay down, blood will be circulated to your skin, leaving less for the heart. If you then stand up, your blood pressure will go down, and you may faint. Lying down is not recommended. If you sleep or pass out in a hot sauna, you will become dehydrated, and death will occur after some hours.
Kukkonen-Harjula: One can sit or lie down. Benches are placed at several heights, thus allowing one to select the appropriate temperature. And in Finnish sauna bathing, one always throws hot water on the stones on the stove to increase humidity and heat; in addition, one can use a bunch of birch twigs to enhance the sensation of the skin.
If your sauna temperature is lower than it was in the Finnish studies (176 degrees Fahrenheit), try to increase your contact with the wood and sit as high as possible.
What are the dangers of excessive sauna exposure? What should I do to recover if I overdo my sauna usage?
Kukkonen-Harjula: One can die in the sauna — of heart attack if the heart is weak, or from excessive heat (hours, drying, or, for example, because of alcohol intoxication).
Leppäluoto: [In a] recent article, there was no upper limit for the health benefits of sauna use.
Kukkonen-Harjula is talking about acute immediate effects, while Leppäluoto is talking about the long-term effects of sauna exposure. In a single session, don’t stay so long that you pass out. In the long term, don’t be afraid to go to the sauna as many times as you have time for.
Should people alternate heat and cold exposure, like going into the sauna and then taking a cold shower?
Kukkonen-Harjula: This is usually recommended, but the cold need not be ice-cold — go with what feels good to you.
Leppäluoto: Usually, between sessions you sit in a cool place or swim in water, sometimes even containing ice, for some minutes and then go back to the sauna. You should consume beverages [during this time], since you will lose 0.2 to 0.6 liters of water every one to two hours. Usually beer and alcohol are drunk, but they are not recommended. In Finland, almost all sauna accidents (falling, burning, even dying) are related to high blood alcohol.
Most likely, your sauna is attached to your gym, and so it will never have occurred to you to pair the sauna with alcohol. That’s good! The Finnish tradition of alternating heat and cold seems to mostly be about recovering enough to go back into the sauna.
Most sauna research seems to come from Finland, where most subjects are already regular sauna users. How much can the results of this research be generalized to other countries?
Leppäluoto: That has been a problem. If someone unaccustomed to using the sauna starts using it, they may experience a high heart rate, bad feelings, EKG changes, blood pressure changes, and fainting. Therefore, an unaccustomed person should start with short sessions, keeping cold water close by. Usually, water is thrown into the oven so that hot steam fills the sauna room. Newcomers should avoid creating much steam during their first few sessions.
Kukkonen-Harjula: This is indeed the problem with epidemiological longevity studies: data are not available from other countries. I would stress the relaxation capacities of sauna bathing and the wellness idea. Sauna studies have also been conducted in Germany (where there is an active wellness industry and saunas are clubs), in Japan, and in Russia (although [researchers there] do not publish much in other languages than Russian).
If you’re new to the sauna, you should feel comfortable starting with five-minute sessions and working your way up from there. Trust that your body will make physical adaptations that will make longer sessions easier. Those physical adaptations will include increased blood plasma and thermoregulatory control.
The Current State of Sauna Research
Much of the current research on saunas consists of epidemiological or population studies, meaning it can establish correlation but not causation. For example, the most famous sauna study looked at 2,300 Finnish men over the course of 20 years and found that those who used the sauna had major reductions in mortality. But there was no control group. A second category of sauna and hyperthermic research has only looked at the effects of sauna usage on rats.
Although the effects of sauna usage haven’t been conclusively determined in the laboratory, you should be able to see the results of sauna use in your own cardiovascular health. Is your performance on the treadmill, in heat, or on an exercise bike improving? If so, then you are getting a cardiovascular benefit. Is building muscle a goal? You can measure yourself whether you increase muscle and strength faster over a three-month period with sauna versus without.
Will regular sauna usage improve your longevity?
This Finnish study says yes: sauna bathing two to three times per week is associated with a 24 percent reduction in all-cause mortality, while sauna bathing four to seven times per week is associated with a 40 percent reduction. That study exhibits a dose-response relationship — the longer and more frequent your sauna sessions are, the longer you tend to live.
Sauna usage is also strongly associated with a decreased incidence of cardiovascular disease. Another study has found that using a sauna two to three times a week is associated with a 23 percent decrease in fatal cardiovascular incidents such as heart attacks, while sauna bathing four to seven times a week is associated with a 48 percent decrease in fatal cardiovascular incidents.
Doctors usually recommend that people with cardiovascular diseases avoid sauna bathing. However several studies have found that this is overly conservative. According to a 2006 article co-authored by Kukkonen-Harjula, sauna use “did not appear to be particularly risky to patients with hypertension, coronary heart disease and congestive heart failure, when they were medicated and in a stable condition. … Medication in general was of no concern during a bath, apart from antihypertensive medication, which may predispose [an individual] to orthostatic hypotension after bathing.”
In other words, sauna usage should be avoided if you have recently had a heart attack but is usually safe if your heart condition is stable.
There are no indications that sauna use presents longer-term dangers—if you don’t have a heart attack in the sauna, you’ll be fine once you get out. Notably, most people who have died in a sauna have been intoxicated at the time of death, and many have also suffered from a heart condition or diabetes in addition to being intoxicated.
The risks for healthy, sober people appear to be minimal. The important things are to stay hydrated, take short breaks every 10 to 20 minutes to rehydrate, and take a break if you start to feel uncomfortable or overheated. Sober individuals typically have no problem following any of these suggestions.
Does sauna usage improve endurance?
Regular sauna use improves thermoregulation and cardiovascular endurance, even in highly trained athletes. These benefits appear to be related to the sauna’s ability to increase stroke volume — the amount of blood pumped per heartbeat.
Sauna usage has strong but short-lived hormonal effects on the body. It massively increases levels of growth hormone and prolactin and also mildly increases norepinephrine secretion. However, these increases dissipate within one or two hours after sauna usage.
Does sauna usage help recovery from exercise?
Sauna usage has been found to mildly increase testosterone levels and decrease cortisol levels. Since the testosterone/cortisol ratio is the best hormonal marker we have for recovery from exercise, this may mean that using a sauna after working out can help you recover faster and may be performance-enhancing. However, these hormonal changes are short-lived, and ultimately what counts is your hormone levels over the long run, not just immediately after working out.
In rats, sauna usage has been shown to stimulate an acute rise in the production of heat-shock proteins (no surprise there). These proteins reduce the oxidative damage suffered by the muscles following exercise.
Dr. Rhonda Patrick makes the case on Tim Ferriss’s blog that heat-shock proteins improve muscle growth. In every hard workout, you’re both damaging muscle and triggering new muscle growth. Theoretically, heat-shock proteins reduce the damage that results from a workout, creating a greater net positive effect.
However, this may actually decrease muscle growth, because oxidative damage is one of the body’s anabolic signaling mechanisms, and a multitude of studies have shown antioxidant supplements actually decrease muscle growth.
On the other hand, another study has found that heat stress reduces skeletal muscle atrophy in non-exercising rats, which may also have implications for injury recovery. These same heat-shock proteins have also been demonstrated to extend lifespan in lower organisms like worms, although a similar effect has not been demonstrated in humans.
It’s also not clear if these changes in blood levels represent changes in the amount of the hormone that is being produced or merely changes in the amount that’s in the bloodstream. It’s possible, for instance, that testosterone goes up because it’s being pushed out of the muscles, which would actually be a negative for muscle growth.
Does sauna usage increase insulin sensitivity?
One study has shown that heat exposure improves insulin sensitivity and lowers fasting blood glucose in obese diabetic mice. This suggests that sauna bathing may be a valuable addition to weight loss and diabetes treatment programs. However, this study was done on mice, and this effect has not yet been proven to occur in humans.
Does sauna usage improve mental performance?
Finally, heat exposure in conjunction with exercise has been shown to increase the expression of brain-derived neurotrophic factor (BDNF), more so than exercise alone. BDNF increases neurogenesis—the production of new brain cells—as well as the survival rate of existing brain cells. Heat exposure has also been found to improve mood in cancer patients, which may or may not be caused by this same rise in BDNF.
Clearly there are a lot of potential benefits from sauna usage, but few have been conclusively proven. Even the association with increased lifespan may be a self-fulfilling prophecy caused by selection bias. That is, because sauna use is labeled as healthy, it could be that healthier people are more likely to engage in it, thus making it associated with good health and long life regardless of whether it works.
Of all the purported benefits of sauna use, the improvements in cardiovascular health are the most well supported by human experiments. I’m convinced that sauna use almost certainly does translate to increases in overall health and longevity.
The other supposed benefits of sauna usage—muscle growth, improvements in insulin sensitivity, and brain health—all need more research before any conclusions can be drawn. Right now, these claims rest almost entirely on rat and mouse studies. Thankfully, this is research you should be able to conduct on yourself.
The claim that sauna usage can help build muscle in particular rests on multiple shaky assumptions. First, it extrapolates findings from rat and mouse studies to humans. Second, it infers the existence of long-term benefits based on studies that only show acute effects. And third, it assumes—wrongly, in my opinion—that oxidative damage to the muscles caused by workouts is a bad thing that should be minimized.
The (Preliminary) Verdict on Sauna Use
If you’re not accustomed to the sauna, the best way to start is to use it immediately after working out for 10 to 20 minutes per session. Take a short break every 5 to 10 minutes, stepping outside the sauna and maybe taking a short shower or getting a drink of water.
Over time you can gradually increase the length of your sessions to a half-hour or an hour (with breaks every 15 minutes). Given that one of the main benefits of sauna use is an improvement in mood, you should spend as much time in the sauna as you like rather than pushing yourself to do more—think of this not as part of your workout, but as something you do to reward yourself after your work out.
Ultimately, sauna bathing is best thought of as an optional addition to a healthy lifestyle. It’s something you should look at adding to your routine if and when you enjoy doing it. Just don’t do it while you’re drinking.