How good are saunas and cold water baths for your health, according to science

But reality, according to experts, is more nuanced.

“Many people swear by exposure to heat and cold, but we still don’t have enough evidence to say that it is categorically beneficial,” says Heather Massey, an associate professor at the University of Portsmouth, UK, who specializes in extreme environments and physiology.

Massey explains that our bodies are “incredibly” capable of maintaining a stable body temperature, typically between 36.5°C and 37°C.

In everyday life, many of us rarely challenge that system, spending long periods in heated or air-conditioned spaces.

However, heating or cooling the body creates a small amount of stress, he says, which can trigger adaptive or protective responses.

For some people, the sauna is a reward after exercise, while for others it is an attraction in itself.

Many regulars recommend it, convinced that 15 minutes of intense heat does wonders for the body and mind.

And it can certainly feel good.

“When you sit in a sauna and sweat, you can feel looser, freer, a little more mobile, and your aches and pains can go away a little bit on their own,” Massey tells the BBC’s What’s Up Docs podcast.

“So there is definitely some benefit to using the sauna, but the question is whether it is a long-term health benefit or more of a psychological thing,” he adds.

Massey notes that in a recent study, several people did repeated hot tub sessions and the results showed changes in insulin and blood pressure.

“We are starting to explore whether warming the body could help people living with chronic illnesses,” he says.

Still, he urges caution with strong health claims, as solid scientific evidence is still limited.

“We’ve never done a proper trial on the sauna,” he says. “I suspect we will find benefits in the future, but we are not there yet.”

For now, he says, it’s reasonable to enjoy the ritual for how it makes you feel, without assuming it’s a guaranteed shortcut to better health.

And if you try saunas or hot tubs, Massey recommends caution: “Start small,” and check with your primary care doctor first if you have any underlying health conditions or are pregnant.

Some people go in the opposite direction. Cold water swimming groups are becoming more popular and morning dips are now common at beaches, lakes and rivers.

Massey, who has swum across the English Channel and competed in the world ice swimming championships, swims in cold water once a week, but only spends a couple of minutes in the water.

It’s painful at first, but that initial shock is just what people are looking for.

“When you first dive, you experience labored, rapid breathing,” he explains. Heart rate and blood pressure increase, and stress hormones, such as cortisol and adrenaline, spike.

“That response peaks at 30 seconds and then declines very quickly,” he adds.

Repeated exposure reduces the impact response and after several short baths it can be reduced by approximately 50%.

As with saunas, the big question is whether the benefits come from the temperature itself or from everything around it.

Cold water swimming is usually practiced outdoors and in company. “It is an activity with multiple mechanisms: nature, movement and social connection, and they are all interrelated,” says Massey.

Podcast host Dr. Chris van Tulleken agrees that it’s difficult to separate those factors: “We don’t know if the benefit is in the cold water itself or in being with a group of fun people and doing something challenging together.”

For Massey, however, the starting point is not temperature, but enjoyment.

“I talk to people who go running every week and they describe the exact same feeling other people experience swimming in cold water,” he says.

“The important thing is to find something that you enjoy, that you can do regularly and ideally that you can share with others, as creating a group of friends around an activity can reduce psychological stress.”

This can be anything from gardening, bird watching, joining a choir, or just walking with friends.

So while saunas and cold baths aren’t essential for good health, Massey says, they can still offer something positive.