When Adam Zolot was ready to expand his paddleboard business into a warehouse-size space on San Francisco Bay, he wedged in one feature that was mostly just for himself: a sauna and cold plunge.
An avid longtime traveler, Zolot had picked up his interest in saunas overseas – in the thermal springs of the Aeolian Islands of Italy, in the onsen bathing culture of Japan, and of course in Scandinavia, the heartland of sauna culture.
He figured he and a few friends would mostly use the four-person barrel sauna and the cold pool he had installed when he expanded Dogpatch Paddle & Kayak to a spot on Illinois Street last year.
But that part of the business took off: He now has regulars, mostly from the neighborhood, but some from around the Bay Area.
“There is an absolute buzz that you will feel after a session” of hot sauna and cold plunge, Zolot said. “You feel dropped into your body and set for the day.”
Dogpatch Paddle is hardly alone in capitalizing on Americans’ growing interest in the pleasures and potential health benefits of sauna and its sister activity, the cold plunge. San Francisco is home to more than a dozen publicly accessible saunas, many of which have opened in just the past few years – and that count doesn’t include private home saunas or others with limited public access.
The science of hot and cold
Saunas are trending now, with aficionados making all kinds of claims about the health and longevity benefits. But this is one trend where the claims are at least partially backed up by the science, say experts in aging.
Large studies in Finland, where sauna is built into the culture, have shown a compelling relationship between sauna use and improved heart health and lower risk of overall death. Other studies have found that heat therapy could help with depression.
The science for cold plunge is less clear, but aging experts say there’s reason to believe that it, too, could promote healthy aging. And some longevity experts believe that sauna and cold plunge together are especially effective.
“In both cases, cold plunge and sauna, they’re deserving of more research,” said Dr. Gregory Marcus, a cardiologist at UCSF. “There is preliminary evidence that there might be benefits for sauna, and we know even less about cold plunges. But like with saunas, there could be very real and potentially meaningful effects on health.”
How to get the most out of a sauna
Saunas are generally kept between 180 and 200 degrees, either dry or with steam, and cold plunges are 32 to 60 degrees. When incorporating both, experts say people should stay in the sauna for about 20 minutes, or until they’re uncomfortable, then stay in the cold plunge for as long as they can tolerate, which is usually one to three minutes. In one session someone may do three rounds of hot and cold.
Small children, people with high blood pressure and those who are pregnant generally aren’t advised to use saunas. They also can interfere with sperm count temporarily. Cold plunges aren’t advised for people who may be at risk of sudden heart failure. But otherwise, both activities should be safe for most people, doctors said.
And saunas in particular are enjoyable for many users. It’s a health trend that many doctors said they support, even if the science isn’t yet strong enough for them to prescribe it. It’s a little bit like the science around caffeine – the health benefits seem to be there, and while the results are mixed, experts generally agree that if people like their coffee, they should enjoy it.
“From a science perspective, generally speaking there’s a lot of good and positive science out there around sauna,” said Zolot. “I have more of an experiential perspective – and it just feels good.”
“I love saunas,” said Dr. Michael Fredericson, a physiatrist and co-director of the Center of Longevity at Stanford. He uses the sauna at his gym after swimming, and he says it’s clearly become more popular in recent years, just based on how crowded it is. He doesn’t have regular access to a cold plunge, and he doesn’t enjoy the experience, “but I feel good when I come out,” he said.
The potential health benefits from sauna are tied to the body’s response to heat, which is a stressor not unlike exercise, Fredericson said. “It’s essentially like you’re exercising, but you’re not exercising,” he said. “You’re getting some of those same benefits.”
Being exposed to high heat can make blood vessels dilate and the heart work harder to move blood and cool the body, which is good for improving cardiovascular health and lowering blood pressure.
Saunas also may trigger activation of a protein called heat shock factor 1, which repairs damage in cells. “By subjecting yourself to controlled heat you are activating this protective response,” said Dr. Eric Verdin, president of the Buck Institute for Research on Aging in Novato. “You’re jacking up the whole protective system.”
Cold plunges come with more questions
Cold exposure is less well studied. Ice baths are well known for aiding in muscle repair after intense workouts, but that’s not something the average person needs, aging experts said. Some small studies have found that cold water exposure may improve metabolism and immune function.
“I don’t know as much about the stress response to cold, but clearly there is a cold response, and it seems to be working at least in part by activating some kind of stress,” said Verdin, who has a sauna at home. “I have friends who have cold plunges at home and we do it, and it just creates this sense of well-being that’s hard to describe.”
Cold plunges are also a lot less fun than saunas. Many people have to build up their tolerance. Verdin recommended starting in the shower, by slowly making the water colder and colder until it’s a full cold shower.
Zolot advises that people, well, plunge into the cold plunge. Dipping a toe and going slow just draws out the torture, he said. “I recommend powering through the first 45 seconds – your mind is going to tell you to get out, but if you can make it 45 seconds your body starts to acquiesce a little.”
Zolot said he feels like he gets the most benefit from the contrast between heat and cold. Sauna, he said, is “calming and relaxing, and I feel like it’s meditative in a sense. When you add the cold plunge it gives you a little bit of a slap.”