Newsletter #167: Saunas for Health and Exercise Performance 🧖
Good morning humanOS friends! This week, we decided to take a closer look at research into the health benefits associated with sauna use.
Various forms of passive heat therapy have been used around the world since ancient antiquity, ranging from traditional Finnish saunas to Turkish baths to onsen in Japan. Of course, most people use saunas or hot baths to relax, but modern science has revealed that saunas are linked to a plethora of interesting physiological effects, like lower risk of heart disease, lower risk of dementia/Alzheimer’s disease, lower blood sugar and blood pressure. It may even boost athletic performance - athletes preparing for the Tokyo Olympics have been using saunas to improve fitness and muscle growth.
Incidentally, you'll notice that a lot of the research elucidating the health benefits of saunas has been conducted by Jari Laukkanen in Finland. Finland is an ideal place to study this phenomenon, as 99% of Finns use a sauna at least once per week (no joke, a Burger King in Helsinki even has a sauna, to give you a sense for how insanely ubiquitous they are). If you’d like to gain some more insight, you should definitely check out our interview with the man himself from a few years ago!
This Week's Research Highlights
🚴 A sauna session has effects on the cardiovascular system that mirror that of a brief workout.
Researchers recruited 19 volunteers and exposed them to a 25-minute sauna session, while having their blood pressure and heart rate assessed. Both blood pressure and heart rate rose immediately during the sauna, but then subsequently dropped below baseline levels after leaving the sauna. On a separate day, the same participants performed a short workout on a stationary bicycle. During the exercise session, blood pressure and heart rate rose to the same levels that they had during the sauna session, suggesting that the bike workout and the sauna session were eliciting similar challenges to the cardiovascular and respiratory systems. Luckily, gyms nowadays are often equipped with saunas, so it’s not too hard to take advantage of both!
🧖 Sauna bathing has acute vascular benefits in older adults with cardiovascular disease.
In a similar study to the one above, 22 older adults with stable coronary artery disease underwent two periods of 10 minutes in a Finnish sauna, separated by 10 minutes of thermoneutral rest. About an hour after, researchers found that the sauna sessions had elevated heart rate (+27 bpm), lowered systolic (-19 mmHg) and diastolic (-6 mmHg) blood pressure, and had increased brachial artery flow-mediated dilation (+1.21%). There is reason to think that these short-term effects on vascular function may translate to long-term benefits - an observational study showed that risk of developing high blood pressure was nearly 50% lower in men using saunas multiple times a week.
🔥 Frequent sauna use is associated with lower systemic inflammation.
Researchers assessed sauna bathing habits in 2269 middle-aged men, and then followed the participants for eleven years. Over the course of the study period, it was revealed that more frequent sauna use was linked to significantly decreased levels of inflammatory markers. Specifically, they found that partaking in 4-7 sauna sessions per week (compared with one sauna session per week) was associated with a reduction of 1.66 mg/L in high sensitivity C-reactive protein (hsCRP), a key biomarker of systemic inflammation. To put that number into some clinical context, the CDC defines the low risk range for hsCRP as less than 1.0 mg/L, and high risk as above 3.0 mg/L. So even though it doesn’t sound like much, a decline of 1.66 ml/L is actually pretty big! And importantly, this association was independent of multiple potential confounding variables, including age, BMI, smoking, health history, socioeconomic status, etc.
🧠 Regular sauna use is linked to lower risk of stroke.
Researchers examined data from 1628 men and women living in eastern Finland. Participants were divided into three groups, based on their frequency of sauna use: those taking a sauna once a week, those taking a sauna two to three times a week, and those taking a sauna four to seven times a week. Over a fifteen year follow-up, the researchers found that the more frequently that subjects used saunas, the lower their risk of having a stroke during the study period. For those who used sauna 2-3 times per week, risk of stroke was decreased by 14%, compared to those who only used the sauna once per week. Participants who used the sauna 4-7 sessions per week were 61% less likely to suffer a stroke, compared to those taking a sauna once a week.
🫀 Men who frequently use saunas have reduced risks of cardiovascular events and death from any cause.
Researchers in eastern Finland (noticing a trend?) looked at data on sauna use and incidence of cardiovascular events and all-cause mortality in a group of 2315 middle-aged men, who were followed for a median of nearly 21 years. Compared to those reporting only one sauna session per week, those who used sauna 2-3 times per week had 22% lower risk of sudden cardiac death, 23% lower risk of fatal coronary heart disease events, 27% lower risk of fatal cardiovascular disease, and 24% lower risk of dying from any cause. Benefits were more pronounced for more frequent sauna use: those who used sauna 4-7 times a week had 63% lower risk of sudden cardiac death, 48% lower risk of fatal coronary heart disease events, 50% lower risk of fatal cardiovascular disease, and 40% lower risk of dying from any cause.
Helpful infographic summing up the benefits of sauna bathing.
Duration of individual sauna sessions also seemed to have an impact. For example, compared to men who spent less than 11 minutes in the sauna, the risk of sudden cardiac death was 7% lower for sauna sessions of 11-19 minutes and 52% less for sessions lasting more than 19 minutes. So you might want to shoot for, over a period, getting up to twenty minutes in the sauna or more to maximize benefits. But also consider that time in the sauna is dependent on temperature. If you’re in a hotter sauna, for instance, the same benefits may occur in shorter periods of time. Which reminds me of the time I was in Japan in a sauna of 212 °F. I could barely handle 7-8 minutes. 🥵
Random Trivia Question of the Week
🤔What is the Antarctic 300 Club? (hint: sauna is involved here)
❄️ ANSWER
Videos We Loved This Week
- Jari Laukkanen: Sauna Use for the Prevention of Cardiovascular & Alzheimer’s Disease. Via Found My Fitness.
- Annamaria Peltokangas: Sauna Culture in Finland. Via UNESCO.
Products We Are Enjoying
Drip Drop
Obviously, whenever you’re doing something that causes you to sweat (whether it be through physical exertion or heat exposure, or both), adequate hydration can become an issue. DripDrop is an oral rehydration solution that was originally developed by a doctor to treat victims of cholera, and is also used now by athletes and firefighters. Each 10-gram serving contains just 35 calories and 7 grams of sugar - half the sugar of a comparable serving of a sports drink - but packs around three times the electrolytes that you find in drinks like Gatorade. And it comes in convenient packets, so it’s easy to carry around in your gym bag.
humanOS Catalog Feature of the Week
See y'all next week!