Can saunas actually improve your health? Is it science or just hot air?
Anthony Morgan investigates the true science of saunas and their health claims
Don't sweat it! Or should you?
Some believe that regularly sweating it out in a sauna can reduce blood pressure, benefit the skin, promote immune function and mental well-being, and even lower the risk of heart disease. But is there any truth to these claims?
In The Nature of Things documentary Sweat!, Anthony Morgan sweats it out in the name of science to investigate some of the health claims about saunas.
Morgan begins in Finland, a country with such a strong sauna culture that in 2020, UNESCO recognized it as an activity with "intangible cultural heritage" for Finns.
The city of Tampere was even declared the sauna capital of the world, making Finland the perfect place for Morgan's first sauna experience.
Saunas are a form of passive heat exposure where the body is exposed to high temperatures, without physical exertion, to induce sweating and relaxation.
Finns have used saunas for hundreds of years to help maintain good health, hygiene, foster social interactions and even deliver babies.
Could these steamy traditions be on to something?
Passive health benefits?
To find out, Morgan meets with cardiovascular epidemiologist Setor Kunutsor, whose research suggests that Finnish sauna use offers a range of health benefits, including reducing blood pressure and decreasing stress.
One of Kunutsor's studies looked at data from more than 2,000 Finnish men, spanning over 26 years. It found that three to seven sauna sessions per week reduced the risk of heart disease by about 60 per cent in those with high cardiorespiratory fitness, suggesting that a combination of good fitness and frequent sauna bathing may be a powerful combination.
In another study, Kunutsor found that moderate to frequent sauna use was associated with a reduced risk of dementia and Alzheimer's disease.
However, other researchers are skeptical, believing that the health benefits of saunas may be more limited.
The power of exercise
Exercise scientist and ultramarathon athlete Nick Tiller tells Morgan that sauna users might appear healthier due to the relaxation and stress relief the environment provides.
"There seem to be some benefits to regular sauna exposure: psychological benefits on health and wellness and quality of life. In terms of the direct physical effects, I'm not quite as convinced," Tiller says.
Sweating, whether from exercise or saunas, serves primarily as a cooling mechanism.
And as the sweatiest animals on the planet, our cooling systems are top notch. Humans have millions more sweat glands than even our closest cousin, the chimpanzee.
But it's the well-established benefits of physical activity — not simply the act of sweating — that is known to drive health improvements.
"If you really want the true health and wellness outcomes, it takes time and it does take effort," says Tiller.
He points out that most studies on sauna benefits are observational, and says that the few experimental investigations that have been conducted "show no difference in cardiovascular function."
For example, a 2023 controlled trial showed that sauna use did not improve markers of vascular health in people with stable coronary artery disease.
Other research suggests that sauna bathing does not decrease long-term levels of cortisol, commonly known as the stress hormone.
But while sweat may not offer significant health benefits beyond cooling the body, it could serve as a useful, non-invasive health indicator.
Not all sweat is created equal
Research suggests that sweat from sauna bathing contains higher levels of minerals such as magnesium and calcium, while sweat from exercise has more metabolic byproducts like urea.
In the documentary, Morgan visits sweat researcher Sira Karvinen and works up a sweat, which he then donates to help confirm her findings: that certain biomarkers in exercise sweat are absent in passive sweat.
By analyzing exercise sweat, Karvinen and her team can also optimize the training programs of Finnish Olympic athletes.
For example, an athlete's sweat sample can help show whether they're getting sick or if they may be recovering from an illness. "If you're only training based on how you feel, it might sometimes go wrong," she says.
Although sweating it out in a sauna may not be the cure-all it's claimed to be, sauna bathing and other passive heat–related activities remain as popular as ever.
Hot yoga studios, for instance, promise to deliver some of the same purported health benefits as saunas.
However, one study found that there was no significant difference between practising Bikram yoga in a heated and non-heated environment when it came to improving participants' vascular health.
Passive heat applications like saunas can also pose risks such as dehydration, heatstroke, low blood pressure, respiratory issues or complications for those with heart conditions or sensitive skin if not used properly.
So while saunas might help melt off some stress, they should be used with caution — and you might want to take any health claims with a grain of salt.
Watch Sweat! on CBC Gem, CBC Television and on The Nature of Things YouTube channel.
