Hot & Healthy
Hot & Healthy - How Heat Exposure Can Extend Lifespan
As with cold exposure, the short-term discomfort of extreme heat leads to long-term benefits, with numerous studies showing that enduring intensely hot sweat-sessions can protect against a range of chronic diseases and extend healthspan. Throughout history, cultures around the globe have independently developed their own forms of therapeutic hot immersion, from Finnish saunas to Japanese sentōs, Russian banyas, Turkish hammams and most recently infrared saunas. Now, a growing body of research is helping us better understand the powerful impact heat can have on health and longevity.
How heat exposure affects the body
When your body is exposed to high temperatures, it compensates by activating cooling processes to reduce core temperature including:
- Increased blood flow to the skin surface to dispel excess heat
- Vasodilation (dilation of blood vessels) to further increase the amount of blood exposed to the outside air, giving the skin a pink flush
- Increased heart rate
- Increased stroke volume (the amount of blood expelled with each pump of the heart)
- Increased blood pressure
If these processes sound familiar, it's because they are very similar to the normal physiological response to exercise. In fact, it’s likely that exposure to heat results in many of the same benefits as cardiovascular exercise! Studies have shown that a 25-minute sauna session is equivalent to a 15-minute jog in terms of calories burned and changes in heart rate and blood pressure [1]. That’s not to say you should replace regular cardiovascular exercise with heat exposure - there are vast benefits to your muscles, mental health and other faculties that only exercise can offer - but for rest days, injury recovery or other times where exercise is impossible, heat can be a useful tool.
Key benefits of heat exposure
- Sauna use reduces the risk of mortality in a dose-dependent manner, which means two or more sessions a week causes a far greater reduction in risk than just one [2, 3].
- Sauna use improves heart function, decreases blood pressure, and enhances arterial flexibility (preventing hardening of arteries) [4].
- Heat exposure activates heat shock proteins, initiating cellular repair mechanisms that extend lifespan [5].
- Heat exposure stimulates the release of growth hormone, helping to build muscle mass [6].
- Regular sauna use has been linked to a decreased risk of dementia and Alzheimer's disease [7].
- A single infrared sauna session was found to alleviate major depressive symptoms in a double-blind randomized controlled trial [8], and repeat sessions caused a sustained decrease in depressive symptoms [9].
- Heat exposure stimulates the release of dynorphin, a molecule that causes the intense feelings of discomfort experienced at high temperatures but which can enhance your future body’s sensitivity to endorphins, elevating baseline mood and heightening positive responses to pleasurable events [10].
How should I bring heat into my routine?
The traditional sauna is the most popular and well studied heat exposure method. You should aim for sessions lasting between 8 and 20 minutes at 80-100°C and research (endorsed by longevity scientist Andrew Huberman) indicates that 57 minutes per week is the minimum needed to realise the powerful longevity benefits we’ve discussed here [11].
Research on infrared saunas has shown promising results, particularly for depression (as mentioned earlier), but the general consensus is that there isn’t quite enough evidence yet to say whether they are as effective as the traditional alternative. Most studies that have demonstrated benefits have used protocols of 15-minute sessions at 60°C, 5-7 times a week [12].
Hot baths or jacuzzis (at around 40°C) have also been shown to bring about some benefits, including cardiovascular impacts and increased heat shock proteins, however they require longer sessions of 30-60 minutes to have an impact [13].
General tips for any kind of heat exposure:
- Heat exposure should feel uncomfortable, but if you start to feel seriously unwell, get out immediately.
- Ensure you stay hydrated to replace the water you lose through sweating. As a general rule you should try to drink 0.5L (or 16 fl oz) of water for every 10 minutes you spend in a traditional sauna. You may also consider taking in electrolytes, especially for long sessions.
- Use heat exposure later in the day to optimise your sleep. Your core body temperature decreases as you get closer to your bedtime in order to help you get to sleep more easily, so in the evening the physiological mechanisms for lowering body temperature are activated and align with the cooling response provoked by heat exposure.
- If you’re combining hot and cold exposure, you should aim to finish on a cold exposure, as metabolism is beneficially stimulated by your body warming itself up.
