It's good to get hot.
Taking a regular sauna is more than just a way to relax, according to a recent medical review of a number of studies published in the journal Mayo Clinic Proceedings. People who take saunas regularly have lower rates of cardiovascular disease and fewer problems with blood pressure.
They also have fewer issues with lung disease, cognitive disease, and mental health, according to that review.
Something about regularly exposing yourself to hot temperatures, which gets your blood pumping much like exercise, seems to be associated with a better quality of life, according to the review.
This provides yet more evidence that it may not be good for us to spend all our time in climate-controlled spaces where the temperature rarely dips below 20°C or creeps above 22°C.
Other research has shown that hot baths can provide health benefits similar to exercise, including reduced inflammation, improved blood sugar, and lower blood pressure. And still other studies have shown that exposure to extreme cold can help people burn fat, improve the immune system, and counteract some effects of type 2 diabetes.
Those findings have led some people — notably athletes and Silicon Valley biohackers — to incorporate cold showers and ice baths into their routines.
The practice of seeking out health benefits by forcing your body to cope with hot and cold temperatures is known as "environmental conditioning" among fitness experts.
Saunas are deeply embedded in Finnish culture. There, taking a sauna as a means of making the body more resilient is known as "hardening".
A sauna — or sauna bath, as some studies describe them — refers to spending a brief period of time in a hot, dry room. According to the study, temperature at head level ranges from 80- to 100°C, while temperatures tend to be lower closer to the floor. People can pour water on hot rocks to increase the room's humidity, which usually varies from 10% to 20%.
People usually spend five to 20 minutes in the sauna, according to the review, though some may spend longer periods of time. Heart rate tends to rise up to 120 to 150 beats per minute for sauna bathers, as it does during exercise, though muscles aren't activated in the same way.
Saunas are considered to be accessible to everyone and the average Finland resident takes at least one sauna a week, though some do it every day.
Because saunas are so common in Finland, researchers have been able to conduct significant research on sauna bathers. In general, they've found that the more saunas people take, the healthier they are.
Many of these studies compare people who take one sauna a week to those who immerse themselves in heat four to seven times a week. Depending on the study, those who hop in the sauna more often see their risks of cardiovascular problems like strokes, high blood pressure, heart attacks, or death drop by 37% to 83%.
Frequent sauna bathers also have more than a 60% reduced risk for dementia and Alzheimer's. Other studies show that people who use the sauna more frequently are significantly less likely to suffer from lung illnesses, psychosis, headaches, and various forms of inflammatory painful conditions like arthritis.
The researchers write that research in Japan indicates saunas may help improve the symptoms of patients with mild depression.
In most cases, researchers can't say that saunas necessarily cause these improvements, just that people who take more saunas seem to have better health in a variety of ways.
However, the authors of the new review write that they think saunas may be beneficial in ways similar to exercise because the body responds in way that's similar to a physical response to exercise. The increase in body temperature causes more efficient skin blood flow and sweating, along with increased activity from the heart. Hormone levels seem to fluctuate in ways that are similar to fluctuations caused by exercise.
There's also evidence that saunas decrease inflammation, boost the immune system, and reduce certain signs of physical stress.
Saunas aren't entirely risk-free. People tend to occasionally burn themselves, especially when they've been drinking. But all in all, a life with more saunas seems to be a healthier one.
It's not just heat that's associated with benefits, either — exposure to cold temperatures also seems to be connected to positive changes in the body. Dutch fitness guru Wim Hof, who goes by the nickname "Iceman," is credited with popularising the colder branch of environmental-conditioning practice.
Hof argues that our circulatory systems are designed to help us adapt to different surrounding conditions. He says that a lack of stress on this system, which comes from always controlling the temperature around us, could be partially responsible for diseases of the circulatory system like hypertension and stroke.
His recommendations include exposing yourself to cold, so that the body becomes more efficient at heating itself.
Earlier this year, a study published in the Nature journal Scientific Reports found evidence that exposure to cold temperatures could transform the type of fat we form in our bodies to a healthier kind of fat, helping us burn off excess body weight.
Other data indicates that Hof's cold exposure method — and an accompanying breathing regimen he teaches — can lead to better fat-burning capabilities, weight loss, improved immune-system function, and the ability to counteract some effects of type 2 diabetes in certain people.
Journalist and anthropologist Scott Carney investigated Hof's method in his book, "What Doesn't Kill Us: How Freezing Water, Extreme Altitude, and Environmental Conditioning Will Renew Our Lost Evolutionary Strength." In it, Carney suggests Hof's concept of environmental stress could be considered a third pillar of physical fitness, alongside diet and exercise.
For those interested in incorporating some of this science into their lives, hot baths and saunas might be easier to add into a fitness regimen than cold showers or ice baths. But perhaps the biggest takeaway might be that a little bit of environmental stress — allowing yourself to feel hot or cold and adapt to that — might be healthier than closely controlling the temperature around you at all times.
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