00:00In the early 1980s, a group of scientists set out to conduct a long-term study on heart health. They focused on Finnish men, recruiting over 2,000 participants and monitoring everything from their behaviors, diets, lifestyle choices, and fitness over the course of 20 years. As they dug into the data, researchers were stunned to find that one habit— something they hadn’t expected— was linked to better health: frequent sauna bathing. Yet this likely didn’t surprise the Finnish participants. Finland is a country with 9,000 years of sauna traditions. And they’re not alone: Roman balneae, Japanese onsen, and Indigenous American sweat lodges are just a few examples of how cultures across the globe have long considered exposure to extreme temperatures therapeutic. But today, scientists are only just beginning to unravel how and why
01:00this may be the case. So, what exactly is happening in your body when you feel the heat? To understand how extreme heat affects the body, let’s explore what happens when you enter a sauna. Traditional Finnish sauna temperatures can top out at 90°C, or just below the boiling point of water, and are typically dry, at about 20% humidity. This blast of dry heat ignites your thermoregulatory response. Specialized temperature-detecting proteins in the skin change shape, triggering sensory neurons to send this high heat message to the brain. Blood vessels widen, and your heart rate ticks up to circulate blood faster. To shield your vital organs from intolerable temperatures, your skin absorbs heat, creeping up to 41°C, and dumps this heat from your body's surface. You sweat. If this response reminds you of exercise, that’s no coincidence. Physiologists who study sauna use have likened the body's heat response
02:00to a moderate workout. And while time in the sauna isn't a replacement for exercise, regular exposure to controlled heat may stress the heart and, over time, strengthen the cardiovascular system in similar ways. Heat may also complement exercise and help aid recovery. In strenuous workouts, muscle fibers acquire microtears. This summons immune cells that help repair and strengthen the tissue. But this process also releases waste, which can cause even more inflammation and pain. Inflammation is a natural phase of healing, but too much inflammation can paradoxically slow recovery. This is where sauna use comes in— physiologists suspect that increased blood flow can help pump in the biological ingredients needed to rebuild and help pump out waste. This give and take between heat and inflammation may even lead to greater health benefits. As we age, cells naturally accumulate more and more inflammatory damage,
03:00which is thought to contribute to different health problems. And there is some early evidence that frequent sauna use could help regulate this inflammation. There’s one more way regular heat exposure may impact health. Molecules called “heat shock proteins” safeguard your cells by repairing damaged DNA and monitoring when important enzymes aren’t functioning properly. And studies show regular sauna users tend to have higher levels of these proteins. So, back to the Finnish findings. Scientists found that men who used saunas four to seven times per week were healthier by several measures, including a reduced risk of high blood pressure, healthier cholesterol, and even a lower risk of dying in general. Despite these promising results, the world of heat offers more questions than conclusive answers. First, the Finnish study was unable to fully rule out how other lifestyle factors may have influenced the health differences they detected.
04:00And even if the results do hold, this study covers just one demographic, from one region, over one period of time. Scientists are still working to understand the full extent of sauna’s benefits, as well as its limits. After all, we already know that heat can affect people differently. For example, an intense thermoregulatory response can be dangerous for pregnant people or those with certain health conditions. So, while it’s not yet possible to declare a true cause and effect between saunas and health, many enthusiasts are optimistic that with further investigation, these beneficial findings will handle the heat.