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The good heat

The good heat

We have all come across jacuzzis, hammams, saunas, and other types of hot baths. While they are very relaxing for most of us, the scientific literature has shown more benefits for one in particular, the dry sauna, also known as the Finnish sauna.

It provides a very mild sympathetic stimulus that triggers the body's adaptive mechanisms without placing physical stress on the body. In simpler terms, it provides a mild stimulus to the body, activating its adaptive mechanisms without causing any harm.

Benefits

Multiple studies have shown that the dry sauna is beneficial for a range of health conditions. A big part of it is due to the fact that it mimics the body's response to exercise: heating, sweating, increased heart rate, and blood flow[1]. And as we know, exercise is one of the three pillars to improve health and longevity.

Saunas have been widely recommended for recovery after intense exercise. Indeed, it has been shown to reduce oxidative stress after a 30-minute aerobic exercise[2]. It has also been shown that heat exposure reduces muscle atrophy (in case of immobilization) by up to 37% compared to a placebo[3]. In the most extreme cases, it can even increase the growth hormone by 16-fold[1].

Not only does it improve recovery, but it tends to reduce cardiovascular-related risks by enhancing blood supply, protecting cells, and reducing inflammation through a increased expression of heat shock proteins. Furthermore, it creates a cardiac response similar to moderate-intensity physical exercise [1][4].

Observational studies have shown that the risk for sudden cardiac death was 63% lower for men who used the sauna 4–7 times per week, compared to men who used the sauna 1 time per week. Men who reported using the sauna 4–7 times per week had a 46% lower risk for developing hypertension, compared to men who used the sauna only 1 time per week [1].

The range of benefits also include cognitive improvements. Again, observational studies showed that men who used the sauna 4–7 times per week had a 65% reduced risk of developing Alzheimer's disease, compared to men who used the sauna only 1 time per week [1][5]. In addition, it increases the expression of brain-derived neurotrophic factor (BDNF), a protein promoting the growth of new neurons[1].

Methodology

The exact procedure for sauna use has not been commonly shared in the literature, but most observational studies rely on the recommended sauna practice, which is as follows:

The sauna should be at a temperature of 80 to 100 degrees Celsius at face level with low humidity (~10-20%). The practice consists of 2 to 3 rounds of:

  • A 5-10 minutes sitting in the sauna
  • Followed by a 2-3 minutes cold shower

This should be repeated 4 times per week to maximise the benefits [1].

It is important to note that, in general, there are no contraindications to sauna use, but people with chronic heart failure or other cardiovascular contraindications should consult with their doctor first. Additionally, consuming alcohol or drugs while taking a sauna can create serious health risks and should be avoided [6].

Longer exposure to heat can also be beneficial, but it should be recommended on an individual basis, and a period of adaptation may be required.

Summary

Heat exposure through dry sauna has a wide range of benefits including:

  • Increasing growth hormones
  • Improving recovery after exercise by reducing oxidative stress
  • Improving brain health and cognitive function
  • Reducing risks of cardiovascular diseases

Observational studies have shown that the more frequently sauna sessions were performed (up to once per day), the greater the benefits. However, it's important to note that such studies can only show associations and not causation.

References

  1. Patrick, R. P.; Johnson, T. L. Sauna; 2021. Use as a Lifestyle Practice to Extend Healthspan. Experimental Gerontology , 154
  2. Sutkowy, P. et al; 2014 The Effect of a Single Finnish Sauna Bath after Aerobic Exercise on the Oxidative Status in Healthy Men. Scandinavian Journal of Clinical and Laboratory Investigation, 89–94
  3. Hafen, P. S. et al; 2019. Atrophy in Human Skeletal Muscle Subjected to Immobilization. Journal of Applied Physiology, 47–57
  4. Ely, B. R.; Clayton, Z. S et al;  2018 Meta-Inflammation and Cardiometabolic Disease in Obesity: Can Heat Therapy Help? Temperature, 9–21
  5. Laukkanen, T. et al; 2017 Sauna Bathing Is Inversely Associated with Dementia and Alzheimer’s Disease in Middle-Aged Finnish Men. Age and Ageing, 245–249.
  6. Hannuksela, M. L.; Ellahham, S. 2001 Benefits and Risks of Sauna Bathing. The American Journal of Medicine, 118–126