I spent my junior year of college in Sweden, studying, drinking snaps and glögg, and trying to adjust to the very dark days of winter (only six hours of daylight). One of my classmates had a sauna at his house, and we would occasionally fire it up and hang out until we were drenched in sweat. Then we’d step outside into the shock of cold air, roll around in the snow, and go back for more. For me, it was a novel and titillating experience. For Nordic cultures, however, sauna is a deeply engrained tradition and a routine part of life.
There’s a good reason for the enduring popularity of saunas, Japanese baths, Indian sweat lodges, Icelandic geothermal pools, and hot springs the world over. “Heat therapy” relaxes the muscles, loosens the joints, reduces physical and mental stress, and just makes you feel good. But there’s increasing scientific evidence that heat therapy also improves multiple aspects of health—and even increases longevity.
Heat Therapy Reduces Risk of Death
In Finland, where sauna originated, they take their “bathing” seriously. The majority of Finns (99 percent, according to some reports) sit in a sauna at least once a week, so this country is fertile ground for studying heat therapy benefits.
Finnish researchers enrolled 2,315 men ages 42–60 in a long-term study to evaluate risk factors for cardiovascular disease. Most of the men reported taking a sauna two or three times a week, some more and some less; only 12 of them never used a sauna at all.
When the research team tracked outcomes 20 years later, they found that the men who took two or three saunas weekly were 22–27 percent less likely to die from cardiovascular and other causes than once-a-week users. And those who spent the most time in a sauna, four or more days per week, had a 63 percent lower risk of sudden cardiac death and a 40 percent reduction in all-cause mortality.
These dramatic decreases can be explained in part by sauna’s ability to minimize stress and its negative impact on cardiovascular health. Heat therapy, however, has powerful physiological effects as well.
Heat Therapy Turns on Protective Genes
Cells respond to high temperatures by turning on stress genes and other protective mechanisms. Nitric oxide (NO) production ramps up to dilate blood vessels and dissipate heat. Heat shocked proteins spring into action to protect against damage, curb inflammation, and reduce cellular death. AMPK is activated to regulate cellular energy and glucose and fat metabolism.
As your core temperature rises, your heart beats faster, cardiac output increases, and circulation improves. These changes mimic the effects of physical exertion, and regular sauna use actually has many of the same cardiovascular benefits as exercise: improved endothelial function, lower blood pressure, higher ejection fraction (an indication of the heart’s pumping capacity), and increased vital capacity (a measure of lung function).
Heat therapy also improves insulin sensitivity and blood sugar control. A small study published in the New England Journal of Medicine demonstrated that when individuals with type 2 diabetes sat in a hot tub for 30 minutes, six days a week for three weeks, fasting blood sugar decreased from an average of 182 to 159, and hemoglobin A1C by a full percentage point.
You can see why enthusiasts consider heat therapy a promising treatment for heart disease, heart failure, hypertension, diabetes, and metabolic syndrome, but there’s more.
Sweat It Out
During a typical sauna session, the average man produces a pint of sweat, or about 1.5 pounds of fluid. The primary purpose of perspiration is regulation of body temperature, but conventional doctors scoff at the idea that it does much beyond that.
They’re wrong. Sweating helps keep the skin healthy by opening the pores and removing impurities that may cause blemishes. (My wife tells me that steam is used during facials for that very purpose.) It releases dermcidin and other antimicrobial peptides that protect against infection.
Perspiration also helps remove toxins that accumulate in the body. Analysis of sweat samples reveals traces of a number of toxins, including mercury, lead, cadmium, arsenic, and the hormone-disrupting chemical BPA. Research suggests that “induced sweating” has great potential for eliminating toxins from the body, and many people report dramatic improvements in physical symptoms and mental clarity after undergoing heat therapy.
Heat Therapy: Versatile, Accessible, and Inexpensive
The Finnish scientists who conducted the sauna study stated that their results can’t be applied to steam rooms, baths, or hot tubs, or other types of saunas. I don’t buy it. Raising the core body temperature, regardless of the method, provides remarkable benefits.
One of my friends sits in the steam room at his gym three days a week after working out, and another soaks in a hot bath for half an hour every chance she gets. My stepdaughter does Bikram yoga in a room heated to 104 degrees and 40 percent humidity. I use an infrared sauna, which I installed in my home 10-plus years ago. I sit in it for about 20 minutes almost every morning after exercising, and since there are no snow banks in my area, I take a cool shower afterwards. (Truth be told, there’s no way I’d roll around in the snow, even if I could.) I may not live to be 100, but it feels great, and I’m convinced it’s doing my health a world of good.
Heat Therapy Benefits Recap
Build up gradually to 10–20 minutes in a sauna, steam, or hot bath three or more days a week. Heat therapy is not recommended for pregnant women but is safe for most people— as long as you use common sense. Drink lots of water, don’t consume alcohol prior to heating up, take a good multivitamin supplement to replace minerals lost in sweat, and if you feel faint or dizzy, get out immediately. Overheating is more likely to happen in a hot tub or steam room because sweat evaporation’s cooling effects are minimized, so monitor time and temperature carefully. Finally, take care getting in and out of tubs and on wet floors to avoid slipping and falling.