As the UK grapples with its fourth heatwave this summer, scientists are examining whether sauna use can enhance our ability to withstand extreme heat. While the sauna trend continues to gain popularity, experts caution against its effectiveness as an immediate remedy for heat-related illness, urging safety and proper hydration instead.
The Growing Sauna Trend
In recent years, saunas have surged in popularity, with many venues promoting them as a means to escape the summer heat. However, as temperatures climb, the UK Health Security Agency (UKHSA) has issued heat health alerts across large parts of England. This comes in the wake of an unprecedented summer, marked by Western Europe experiencing its hottest June on record.
Nicola Pegues, who oversees operations at the not-for-profit Community Sauna Baths, observed an initial decline in bookings as temperatures rose. Yet, she notes a resurgence, attributing it to the outdoor nature of their facilities, which feature both saunas and cold plunges. “You get real relief out of it, actually,” she stated, emphasising the appeal of alternating between heat and cold.
The Science Behind Heat Training
Professor Jari Laukkanen, a cardiologist at the University of Eastern Finland, has conducted extensive research into the health benefits of saunas. He posits that regular heat exposure can train the body to better manage high temperatures. “This is well established in sports physiology, where athletes deliberately use repeated heat exposure to improve heat tolerance before competing in hot environments,” he explained.
Laukkanen highlighted several physiological adaptations that occur with repeated exposure to heat, such as more efficient sweating, enhanced skin blood flow, increased plasma volume, and reduced cardiovascular strain during subsequent heat exposure. “In other words, regular heat exposure may help the body regulate temperature more efficiently,” he added.
Dr Jessica Mee from the University of Worcester is currently recruiting participants for a study investigating whether regular hot water immersion can improve the body’s response to heat. She noted that individuals accustomed to heat tend to pace themselves better, stay hydrated, and recognise their own warning signs earlier.
The Risks of Heat Acclimation
However, the benefits of heat acclimation are not universal. Dr Heather Massey, an expert in extreme environments and physiology at the University of Portsmouth, pointed out that the effectiveness of adaptations heavily relies on the body’s ability to sweat and maintain skin blood flow. Moreover, certain individuals should avoid saunas altogether, including those with acute illnesses or conditions such as unstable angina or uncontrolled low blood pressure.
Experts recommend that heat training involves 40 to 60 minutes of exposure each day for a minimum of four to six days, with benefits lasting about a week. Nevertheless, Laukkanen cautioned against the misconception that saunas offer immediate protection from heat-related illnesses during a heatwave. “The benefits are more likely related to long-term adaptation through regular heat exposure rather than using a sauna as an acute treatment during very hot weather,” he said.
Dr Mee added that heat acclimation is a preparation strategy for milder months, not a coping mechanism for the hottest days of the year. On particularly hot days, using a sauna can compound existing thermal stress, especially if individuals are already dehydrated and sleep-deprived. “You are stacking one thermal challenge on top of another,” she warned, noting that this profile can lead to heat-related illnesses.
Safe Practices During Heatwaves
While studies on heat acclimation have typically been conducted in controlled environments, Dr Mee expressed concerns regarding the safety of unsupervised sauna use at home. “We do not yet know how safely or effectively this transfers to people doing [hot baths] unsupervised,” she cautioned, adding that the immediate risk of fainting should not be overlooked.
In light of the current heatwave, Laukkanen reiterated the importance of following public health advice. “Regular heat exposure is not a substitute for staying hydrated, avoiding strenuous activity during the hottest part of the day, and looking after vulnerable people,” he concluded. These remain the most crucial measures for safeguarding health during extreme temperatures.
Why it Matters
As climate change fuels increasingly severe heatwaves, understanding our body’s response to extreme temperatures is more critical than ever. While saunas may offer long-term benefits for heat acclimation, they are not a panacea for immediate heat stress. Prioritising hydration and safety is essential in protecting against heat-related illnesses, particularly as we face a future where such extreme conditions may become the norm.
