The science of sauna use
While saunas may be unavailable for most people right now, the vast benefits of their use are still worth knowing. They have been used for centuries, originating in Finland, with the initial aim being to provide warmth. Other cultures also used saunas for those sick with disease, hoping that they would profusely sweat and be purified of the disease.
While saunas are used mainly for relaxation, there are also numerous health benefits. This blog will explore the benefits that have been linked to sauna use through academic studies and research.
Infrared sauna v traditional dry sauna
Infrared saunas are a more modern version of the traditional sauna, using infrared heaters to radiate infrared light. This light is felt as heat, which then warms the body directly. The main difference between them is the source and intensity of the heat. While infrared saunas are around 50-60 degrees Celsius, traditional saunas are typically 70 – 100 degrees Celsius. While some of the research around sauna use has found that heat of 80-90 degrees Celsius is optimal(1), infrared therapy also comes with its own benefits which we have written more about here.
Traditional dry saunas are considered to be better for you than high humidity saunas, due to their impact on sweat. When the humidity is too high, sweat won’t evaporate as easily, and this reduction in evaporative cooling leads to more strain on our cardiovascular system. The potential for removing toxins via our sweat is also reduced in a high humidity environment.
How saunas can help with cardiovascular health and circulation:
Saunas may have significant benefits for your cardiovascular system. When using a sauna, your heart rate can increase to 100-150 beats per minute, depending on the temperature(2) and individual. This not only replicates passive medium-intensity exercise, but blood pressure and heart rate post-sauna have been shown to be below pre-sauna levels(3).
A number of studies have found that sauna use can be effective in supporting healthy blood pressure levels, boosting circulation and improving blood flow(4). Further, another study discovered that blood pressure dropped for individuals with type 2 diabetes after using an infrared sauna(5).
Using a sauna often (4-7 times a week), and for a suitable amount of time, is significantly and negatively correlated with cardiovascular disease events for middle-aged to elderly individuals(6). It is expected that frequent sauna users are half as likely to be a victim to cardiovascular-related deaths, when compared to non-sauna users(7).
Sauna use and cognitive health:
Sauna use can have beneficial impacts on cognitive health and function, and has been shown to provide a potential barrier against cognitive decline, depression and poor focus(8). The blood flow requirements of a healthy brain are significant, and sauna use is known to increase cerebral blood flow which is one possibe reason behind these impacts(9). As well as being a relaxing leisure activity, sauna use has been shown to reduce the possibility of dementia and Alzheimer’s disease, and it may help to reduce mild symptoms of depression(10)(11).
Even a single sauna session may have lasting benefits for mental health. In a randomised, double-blind study on depression, people who were exposed to a single sauna session experienced an “acute antidepressant effect that was apparent within a week of treatment and persisted for six weeks after treatment”(12). In another study, sauna use was found to reduce symptoms of appetite loss, struggling to relax and generally negative reports of well-being(13).
In terms of cognitive function and concentration, further research has found that after using a sauna, participants norepinephrine levels increased(14). Norepinephrine is a chemical within the body that prepares the mind for action and helps concentration.
How sauna use reduces inflammation and supports immune health:
In general, thermotherapy for the body has been found to have a negative relationship with inflammation pathway activities(15). More specifically, saunas have been found to help decrease inflammation and support the immune system. One study found that sauna use can increase IL-6 and IL1-RA levels in healthy individuals(16). IL-6 is a cytokine which the body produces when tissue damage and infection is detected and has been found to help with rheumatoid arthritis (RA)(17). Similarly, IL1-RA has been suggested to help with RA, as well as potentially reducing osteopenia, a bone loss condition(18).
Optimise athletic performance with sauna use:
Sauna use provides a passive way of mimicking exercise in the body and can help with muscle recovery and endurance. Sauna use has also been suggested to increase red blood cell count. Higher levels of red blood cells (RBC) help to optimise athletic performance(19). The mechanism behind this may be related to the hormetic effect of heat stress in the form of heat shock proteins.
Heat shock proteins are created when the cells experience higher temperatures than they are used to, such as in a sauna and during exercise. As the job of heat shock proteins (HSP) is to search for damaged proteins and ensure that they are recovered, an increase in HSP activity has been related to stronger biochemistry and increased longevity(20).
Sauna use can trigger heat acclimation, which is the set of changes that we undergo in response to heat stress within a controlled environment. Heat acclimation can support the preservation of muscle mass by helping to increase HSP and growth hormone release, as well as decreasing oxidative damage within the muscles(21). This means that saunas can be especially beneficial for those recovering from minor injuries, who may be unable to exercise.
Saunas can be much more than just a leisure activity, with numerous benefits that contribute to general wellbeing. Using a sauna can support healthy blood pressure levels, circulation and blood flow, positively impacting cardiovascular health. In turn, a healthy cardiovascular system can aid cognitive health also.
Saunas may also help to decrease inflammation and support immunity by creating an increase in IL-6 and IL1-RA levels. Both of these have been found to help with rheumatoid arthritis (RA).
Finally, sauna use can optimise athletic performance by improving endurance and red blood cell count, triggering heat acclimation which helps to preserve muscle mass.
Sauna use can affect people differently, so it’s important to investigate whether it’s suitable for you. The length of time spent within a sauna should be investigated to find the optimal time for you. Consult a health professional before frequent use of saunas.
When using a sauna, keep track of time spent inside and be aware of dehydrating and electrolyte loss. Drinking plenty of water and replacing salts that you will have lost through your sweat is vital to staying hydrated during, and after, your sauna.
Would you like to know more about the science of sauna use? Check out Dr Rhonda Patrick's in-depth sauna research over at FoundMyFitness.
1 Association between sauna bathing and fatal cardiovascular and all-cause mortality events
2 Cardiac Responses to Thermal, Physical, and Emotional Stress
3 The blood pressure and heart rate during sauna bath correspond to cardiac responses during submaximal dynamic exercise
4 How Sauna Use May Boost Longevity
5 Do Far-infrared Saunas Have Cardiovascular Benefits in People with Type 2 Diabetes?
6 Sauna bathing is associated with reduced cardiovascular mortality and improves risk prediction in men and women: a prospective cohort study
7 Association between sauna bathing and fatal cardiovascular and all-cause mortality events
8 How Sauna Use May Boost Longevity
10 Sauna Bathing and Risk of Psychotic Disorders: A Prospective Cohort Study
11 Repeated Thermal Therapy Diminishes Appetite Loss and Subjective Complaints in Mildly Depressed Patients
12 Whole-Body Hyperthermia for the Treatment of Major Depressive Disorder
13 Repeated Thermal Therapy Diminishes Appetite Loss and Subjective Complaints in Mildly Depressed Patients
15 Clinical Effects of Regular Dry Sauna Bathing: A Systematic Review. Evidence-Based Complement and Alternative Medicine
16 Impact of Finnish sauna bathing on circulating markers of inflammation in healthy middle-aged and older adults: A crossover study
17 The role of Interleukin 6 in the pathophysiology of rheumatoid arthritis
18 Inhibition of Interleukin-1 as a Strategy for the Treatment of Rheumatoid Arthritis
20 Heat Shock Proteins and Exercise in Humans