Still, the findings suggest that saunas may help improve cardiovascular function, said Setor Kunutsor, an associate professor at the University of Leicester in England who has been involved in some of these studies. That may be because, generally speaking, short bouts of intense heat stress our heart in beneficial ways — and strengthen the cardiovascular system over time, Dr. Kunutsor said.
When we’re exposed to extreme heat, our hearts pump faster, circulating more blood through our body to cool us down as it would during exercise, said Dr. Daniel Gagnon, a researcher at the Montreal Heart Institute who has also studied the potential cardiovascular impact of heat therapy. This could explain why regular sauna use has been tied to lower rates of cardiovascular calamities, he said, but scientists haven’t definitively proved that saunas themselves can be protective.
“So far, we’re really missing the link to say, ‘Yes, for sure, it does something,’” he said. But the heart’s response to heat might mimic mild exercise, he said, perhaps like a light ride on a stationary bike.
“We know that the more you work a muscle, the better a shape it’s in, and the longer it lasts,” said Dr. Rita Redberg, a cardiologist at the University of California, San Francisco.
People with heart conditions, like angina or congestive heart failure, should speak to a doctor before going to a sauna, said Dr. Melinda Ring, director of integrative medicine at Northwestern Medicine. Pregnant women should also consult their physician. And if you’re already at the risk of getting dehydrated — for example, if you’re intoxicated — you should also steer clear of the sauna, she advised.
Steam and mirrors
Some spa companies advertise the illusion of a sauna “detox” — the idea that sitting in the heat or steam can leach chemicals from your body. “There’s this image of, ‘All the sweat is going to carry these toxins out,’” said Dr. Ring. “That’s really not how it works.” It’s not clear that sauna therapy can lower overall toxin loads in the body, she said.
