The Emerging Science of Saunas

Sweat houses have been used by cultures for centuries. Now research is supporting claims that they’re good for health.

Credit: deliormanli/Getty Images

FFinland is a country that boasts over 3 million saunas for some 5.5 million people. Like many Finns, Jari Laukkanen, a medical doctor with the Central Finland Health Care District and cardiovascular researcher with the University of Jyväskylä, has made sauna sessions a daily part of his life. He tries to go once a day, using a sauna inside his home. “Afterwards, it’s like you’re a new person,” he says.

Laukkanen says he gets some of his best ideas in sauna. During one particular session a few years ago, he wondered if there was any scientific basis for his relaxed post-sauna feelings.

He discovered that research into the medical effects of sauna use is somewhat scant. “There are some old studies on sauna, but they were very small, and from years ago,” says Laukkanen. So Laukkanen decided to conduct a series of studies of his own. He’s now produced several medical studies that dive deep into the relationship between regular sauna use and a variety of health benefits, and experts say his work is contributing to an uptick in interest in saunas from wellness seekers around the world.

InIn Laukkanen’s initial 2015 study, he looked at 2,315 healthy Finnish men aged 42 to 60 who had regularly used saunas for the last 20 years. “There were Finnish and also Japanese studies, but not many populace studies, with follow-up. This was possible in our study for the first time, ever.”

Laukkanen and his colleagues found that the more often the men in the study visited the sauna — where they were exposed for a brief period of 20 to 30 minutes to temperatures between 176 to 212 degrees Fahrenheit — and the more time they spent there, the less likely they were to suffer from sudden cardiac death, fatal coronary heart disease, and cardiovascular disease. Men in the study who said they went to the sauna four to seven times a week also had around a 65% lower risk of developing Alzheimer’s and dementia than the men who only went to the sauna once a week.

“Finally we can say the sauna itself is important.”

Laukkanen’s subsequent studies, including an article published in the journal Mayo Clinic Proceedings, also found that people who visited saunas at least four times a week had a more than 60% lower risk of stroke compared to people who went once a week. Other data he found during his research indicated that sauna use was associated with improved lung function, longer lifespan, and less pain from arthritis and headaches. People who visit saunas also frequently report an endorphin high.

“The really big numbers were unexpected,” says Laukkanen, who emphasized that more studies are needed, including research to determine how long-lasting the positive effects of sauna use are on measurements like blood pressure. But “finally we can say the sauna itself is important.”

Perhaps unsurprisingly, Laukkanen’s studies have generated a good deal of international interest in the ancient practice of Finnish sauna bathing. “I’m getting several emails a week from people who have read Jari Laukkanen’s work,” says Risto Elomaa, president of the Helsinki-based International Sauna Association. “In Finland — the country is full of sauna. But many other countries don’t have them, and the health effects are motivating different organizations to be interested.”

For purists like Elomaa, only the traditional Finnish smoke sauna, which is heated by burning wood, really counts. He calls the electrical versions widely used in Finnish urban centers and in saunas outside of Finland “toaster saunas,” but grudgingly admits that these electrical stoves — which rely on coils to heat stones, which water is then poured over to generate heat — are indeed part of the sauna family. (Laukkanen’s studies used electrical saunas). Infrared cabins — which use light to create heat, rather than generating electrical or wood-burning heat to warm the air, and do not get as hot as a regular sauna are gaining popularity in the U.S. — do not count as saunas at all, in his opinion. “The way they heat the body is completely different,” he says, since an infrared sauna heats the body without warming the air.

Researchers like Laukkanen are still trying to understand why saunas might confer health benefits. Some mechanisms are fairly straightforward: A typical hot and dry Finnish sauna increases body temperature, which can cause more efficient blood flow to the skin, says Laukkanen. This, in turn, leads to increased cardiac output, while blood flow to internal organs decreases. Meanwhile, increased sweating is accompanied by a reduction in blood pressure and a higher heart rate. Once out of the heat, the body’s heart rate decreases — just as it does after exercise.

Regular sauna bathing may also improve cardiovascular function because the heat causes cells lining the surface of blood vessels to dilate, improving blood flow and circulation. Sauna use may also reduce arterial stiffness and modulate the autonomic nervous system, which is associated with lower blood pressure and cardiovascular disease risk. Further, the feelings of relaxation and well-being associated with sauna sessions might be linked to the increased production of circulating levels of hormones such as endorphins, which are linked to feelings of relaxation, improved mood, and pain reduction.

“Evidence suggests that the responses produced by an ordinary sauna bath correspond to those produced by moderate- or high-intensity physical activity such as walking,” says Laukkanen (though exercise still provides plenty of benefits worth pursuing). “Further evidence is needed to find the mechanistic pathways.”

TThe Finnish are not alone in their love of sauna culture. In fact, many countries have an active sauna practice. “Sweat baths” is the catchall term, which includes the Finnish sauna, Russian banya, Turkish hammam, and Native American sweat lodge, among others. In Germany — where people are more likely to sauna with strangers in one of the country’s 12,000 public or semi-public saunas than in Finland, where the lion’s share of saunas are private home saunas — the health benefits of saunas are fairly well recognized. Rainer Brenke, the medical doctor for the German Sauna Association, said that in East Germany, doctors could even prescribe sauna visits as treatments (with the demise of the German Democratic Republic (GDR), this practice ended). The practice of switching between a hot sauna and freezing cold water or snow is a beloved tradition in Finland, and one Brenke believes is most beneficial. “It’s really the contrast between hot and cold that brings the health benefits,” he added. “If you just go in the heat, it feels good but it doesn’t have the same effects, like reducing the number of flu viruses and colds you get.”

Over the years, Brenke has noticed a shift in attitudes, as the sauna has gone from a health treatment to a leisure activity in Germany. “For me as a doctor, the sauna is undervalued,” he said.

When I found out I was pregnant, I was glad to hear from my gynecologist that sauna visits were fine, and for a period, I found it was one of the few things I still enjoyed. Brenke confirmed that this was normal, in Germany. “Pregnant women can go in the sauna, no problem,” he said. “As long as it is an uncomplicated pregnancy. In fact, it could be helpful, improving the blood flow to the pelvic floor.”

Mikkel Aaland, a Norwegian-American photographer, traveled around the world in the 1970s, researching sweat baths for his book, Sweat. He’s now in the process of revisiting nine of his original destinations for a TV series that will look at what has happened in the bathing cultures around the world over the last 40 years. He says that bathing practices are a reflection of the larger culture. Sweat bathing, which encompasses social, spiritual, and physical elements, is something that “humans fundamentally like to do, and they have found a lot of ways to do it,” he says.

“What I am finding is thrilling me,” says Aaland, who grew up with a Norwegian father, who built a homemade sauna in their house. “In the ’70s, I was living in Berkeley, and we had a tent sauna. But we were hippies.” Now, however, he is seeing a much more widespread adoption of sweat bathing practices. “Millennials, who have grown up with all this technology, are looking for an authentic experience, with tradition. There is an explosive interest in bathing culture.”

While several of the Finnish and German experts I talked to expressed doubt that Americans would ever take to the sauna — not least because of the nudity involved — Aaland hopes that this global surge in interest will one day make its way to the mainstream in the United States, too. “I have a fantasy that instead of Starbucks or McDonald’s on every corner, we would have a bath,” he said. “I feel like I’m like Julia Child, bringing French food here. I’m trying to bring bath culture.”

Studies like Laukkanen’s could help with sauna adoption in the United States, he believes. This echoed a common theme I heard from sauna experts — namely, in countries where sweat bath usage is not the norm, it is health statistics like Laukkanen’s that will convince new users to give the sauna a try.

“Wrap a towel around you, or even though I hate it, wear a bathing suit — whatever it takes to get you in there,” says Aaland. “The rest happens naturally.”

Sally McGrane is a Berlin-based journalist, and writes about culture, business, politics, and science. The spy thriller“Moscow at Midnight” is her first novel.

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