As I’ve written about before, I’m constantly searching for therapeutic tools that are low-risk and high-upside. Dietary strategies, exercise, stress management techniques, sleep habits, and many nutraceutical supplements fall into this category of interventions that have few downsides and the potential to improve health in many different ways simultaneously. One such intervention that continues to show impressive outcomes in the scientific literature is sauna use.
Saunas, while relatively widely available in the United States in many gyms and spas, are even more commonly used in many other countries around the world. Finland is perhaps the most famous example, with nearly one sauna for every two people in the country! Saunas are thought to have originated in northern Europe perhaps around 2000 B.C, possibly even earlier. Saunas were originally heated by placing stones over a wood fire and then intermittently pouring some water on the stones to create some steam and further heat the space. They were initially used not simply for relaxation but for survival in frigid temperatures, along with allowing for a safe and warm place for important events such as human births.
Today, the majority of saunas are heated electrically rather than burning wood. You may have heard the terms “wet” or “dry” describing different kinds of saunas. These descriptors can mean different things to different people, but typically the “dry” sauna refers to the traditional Finnish-style sauna where the space is heated by warmed rocks and water poured over the rocks. This does create some level of moisture, but dry saunas have vents to filter out much of the steam.
“Wet” saunas typically refer to steam rooms where steam is pumped into the room and humidity is very high. In these saunas, the temperature in the room doesn’t reach the same kind of heights as it does in the dry saunas—but it may feel warmer because of all the moisture. We don’t have quite as much research on the effects of these kinds of saunas, but that doesn’t necessarily mean they aren’t also conducive to health benefits.
Additionally, you may have heard of “infrared” saunas. These refer to sauna therapy where heat is generated from red light. This red light heats the body directly, and because the body can absorb certain wavelengths of infrared light, there may be unique benefits to this kind of therapy distinct from the traditional sauna. This is an exciting area of research, but we just don’t have as much of it yet as we do for traditional sauna, and I won’t dive into this topic further here.
As I mentioned, there is a growing body of research that continues to point toward sauna therapy as highly beneficial to health and longevity. Typically, when analyzing research we look to the randomized clinical trials for the highest level of evidence. We don’t have too much of that for sauna, but at a certain point the amount and consistency of non-randomized research can be good enough for us to draw some conclusions from, and that is how I look at sauna research.
A 2015 study published data after tracking 2,315 middle-aged men (I’ll discuss research including women as well) for over 20 years. They found that sauna use was associated with a significantly reduced risk of sudden cardiac death, heart attacks, and even reduced risk of death from all-causes. Not only that, but the number and length of sessions was linearly correlated with better outcomes, meaning the more people were in the sauna, the better they did. There was a staggering 40% reduction in all-cause mortality (meaning death from any cause) in those who did 4-7 sessions of sauna vs those who did 1 weekly.
A 2017 paper looking at the same group of men found that using sauna 2-3 times per week as compared to once weekly led to about a 20% decreased risk of dementia and Ahlzeimer’s, with an incredible 65% reduction for those who used sauna 4-7 times a week. You may be wondering why these studies are comparing multiple times a week to once a week, as opposed to comparing people who didn’t use any sauna. This is because in the Finnish population studied, it’s rare to not use the sauna at all. It would be ideal to have more data comparing any level of sauna use to no sauna use at all, but I think we can safely assume any level of sauna therapy is likely to carry some benefit—with more being better.
An important 2018 follow-up looked at sauna bathing habits in 1,688 people, over half of whom were women. This analysis confirmed that increased frequency and duration of sauna was associated with reduced risk of cardiovascular events in women as well.
Some of these numbers are incredible, but we do need to recognize that because these were not randomized trials that there can be confounding variables. For example, those who go to the sauna more often are likely to also be more health-conscious and make other good decisions for their health. Researchers attempt to control for many of these kinds of variables, but this is always a limitation of an observational study vs a controlled trial in which people are randomly assigned to different treatment protocols. Still, the magnitude of the impact and consistency across studies are impressive enough to suggest there is really something here.
Other reported or potential benefits of sauna include relaxing muscles and improving muscle or joint paints, stress relief, improved sleep, improved detoxification, reduced blood pressure and cholesterol, and improved immune function (in one small trial those who were using sauna had reduced risk of the common cold).
Why Is Sauna Therapy So Helpful?
We don’t know all of the reasons why sauna use may be associated with so many benefits, but there are several probable mechanisms. Sauna elevates the heart rate and “exercises” the circulatory system (not through your muscles of course). Sweating provides its own benefits in helping the body eliminate toxins and waste products. During a session blood pressure and arterial stiffness are reduced, and vascular endothelial function is improved.
Like exercise, the heat from a sauna can be seen as a beneficial “stressor” on the body. Even though when you lift weights you technically damage your muscles, we all know this is a beneficial process as the body responds and adapts by building even more muscle. Similarly, sauna therapy is a stressor that even temporarily increases some inflammatory cytokines such as IL-6. However, acute elevation of IL-6 can actually then lead to anti-inflammatory effects in response. Sauna therapy also activates something called heat-shock proteins in your cells, which help with repairing damaged proteins in the body, slow muscle atrophy, and may protect against neurodegenerative disorders. You also of course sweat in the sauna, which will help with detoxification.
Lastly (and crucially), sauna is often a time of relaxation, mindfulness and rest for the body and mind. I think that cannot be undersold as one of the most important reasons we see so many benefits from sauna therapy. We could all probably use more regular healthy habits that induce a state of relaxation or mindfulness, whether in the sauna or not.
Sauna therapy is a very safe, low-risk intervention for the most part. But there are a few situations in which it may not make sense to undergo regular sauna therapy. If you are a young male looking to conceive, regular dry sauna at high temperatures may reduce sperm count and quality. This is unsurprising given that we know sperm are sensitive to high temperatures, which is why the scrotum hangs off of the body to allow for a cooler temperature. In one study, twice weekly 15-min sauna sessions at 80-90 degrees Celsius (176 to 194 degrees F) reduced sperm count and quality, but this was reversed within 6 months of stopping sauna use.
Additionally, because the sudden change in temperature is a stressor on the body, there are certain people with cardiac conditions who may be at risk using a high-temperature sauna. This would include those with unstable angina, a recent heart attack or severe aortic stenosis. However, using the sauna should be safe and arguably highly beneficial for most people, even those with pre-existing heart disease.
In summary, I see sauna as an incredibly useful intervention to help push health in the right direction, and one of the best tools we have for preventing health problems down the line. We don’t all have saunas in our homes like many of the Finns, but we probably have access to one at a local gym or spa. Additionally, some portable saunas are becoming more affordable, and though they may not operate exactly like the classic dry sauna, I think there is reason to believe many of the health benefits reported above are likely to be seen in any form of therapy in which we are safely exposing our bodies to heat stress.
To be sure, we still don’t yet fully understand exactly which aspects of the sauna are most critical for its benefits. But I would assume we can likely mimic many or most of these benefits even if we don’t have easy access to a sauna. For example, there is reason to believe that warm baths could accomplish many of the same benefits. This study set out to see if bathing saw many of the same cardiovascular benefits as sauna, and found that the frequency of bathing was associated with significant reductions in risk of stroke, heart attacks, and overall cardiovascular disease. Those who bathed nearly daily vs 0-2 times weekly had 28% less risk for cardiovascular disease and 26% less risk of strokes. So if sauna isn’t a realistic option for you, perhaps more frequent warm baths are!