The Evidence on the Benefits of Sauna

Sauna use is becoming increasingly popular with a number of facilities offering the service and promoting numerous health benefits associated with it. From a subjective standpoint, sauna users report that a deep, healthy sweat relieves stress, reduces muscle tension, and delivers an overall sense of relaxation and well-being. Today we are going to dive into the science behind it and look at what the evidence actually says.

What is Sauna?

Let’s keep thing simple and call sauna what it is, which is mode of heat therapy. Heat therapies have long been used for healing and wellness, dating all the way back to the ancient Greeks, Romans, and Mayans. A sauna is really just a room designed specifically to help you sweat by generating heat. What’s exciting though about Sauna is that not only does it feel good but we now have some scientific evidence behind saunas and its clinical health benefits. How goods that!

Types of Sauna

There are a number of different types but the good news is the health benefits across them all is relatively consistent. While across cultures there are a number of types including the Finnish outdoor saunas, Swedish batsu, the Korean jjimjilbangs, and Japanese sento, you may be more familiar with the conventional dry and steam (or wet) saunas, as well as the latest infrared saunas, all offering a variety of health benefits. 

Conventional vs Infrared

Conventional saunas generate body heat by heating the air and room temperature around you. This is done with fire, hot stones, gas or electricity. Then the wet sauna is just the application of water on theses elements to generate steam and therefore more heat. Infrared sauna on the other hand delivers direct heat to the body. They generate heat by emitting infrared light that delivers radiant heat that’s absorbed by the surface of the skin. 

Looking at the Evidence and Mechanism

A systematic review was performed by Hussain J and Cohen M collating and reviewing 40 papers since 2000 onwards looking into the mechanism and effects of repeated dry sauna and infrared interventions on human health.

Several mechanisms of action have been proposed for the health effects of frequent sauna but the key primary effects of exposure to heat are:

• Increases cardiac output 
• Reduces peripheral vascular resistance 

These 2 factors induce other physiological changes in cardiovascular parameters such as:

• Decreased systolic and/or diastolic blood pressure 
• Increased HRV (heart rate variability) 
• Improved cardiac function markers
• Improved flow-mediated arterio- and vasodilatation of small and/or large blood vessels

Regarding hormonal and metabolic models:

• Reduced levels of epinephrine and/or norepinephrine 
• Increased levels of nitric oxide metabolites in blood and urine 
• Decreased total and LDL (low density lipoprotein) cholesterol levels 
• Increased serum levels of growth hormone, adrenocorticotropic hormone (ACTH), and cortisol 
• Decreased fasting blood glucose levels 
• Increased plasma ghrelin levels 
• Reduced urinary levels of prostaglandins (8-epi-prostaglandin F2α) 

The systematic review established that these findings “support complex multipathway end-organ effects on the central and autonomic nervous system, the peripheral vascular endothelium, and the hypothalamus-pituitary-adrenal axis, as well as on the kidneys and the liver that are continuing to be documented.”

While most of the evidence shows the effects of sauna on the decreased risk cardiovascular disease, other conditions have also been explored. There is evidence showing that sauna may benefit people with rheumatic diseases such as fibromyalgia, rheumatoid arthritis, and ankylosing spondylitis, along with individuals with chronic fatigue and pain syndromes, chronic obstructive pulmonary disease, and allergic rhinitis. Sauna has also been suggested to improve exercise performance in athletes, skin moisture barrier properties, and quality of life.

Adverse effects

Most studies reported beneficial health effect with only one reporting adverse health effects specifically regarding disrupted male spermatogenesis. Effected parameters included:

• Reduced sperm counts 
• Reduced sperm concentrations
• Fewer motile sperm 
• Abnormal sperm parameters (histone-protamine replacement, chromatin condensation, mitochondrial function)

Now don’t be too alarmed because these effects were shown to be temporary. All of the above changes were shown to return back to normal levels 6 months after ceasing sauna activity

There is not yet enough evidence to distinguish any particular health differences between dry and infrared sauna bathing. Further study is needed to determine the optimal frequency and duration of distinct types of sauna bathing for targeted health effects and the specific clinical populations who are most likely to benefit. But with so many proposed and recorded benefits, the bottom line seems to be this.. Go get your sweat on!

Important note: If you have any pre-existing cardiovascular conditions and are unsure if sauna is appropriate for you ensure that you are cleared by your GP first.

References:

Hussain J, Cohen M. Clinical Effects of Regular Dry Sauna Bathing: A Systematic Review. Evid Based Complement Alternat Med. 2018 Apr 24;2018:1857413. doi: 10.1155/2018/1857413. PMID: 29849692; PMCID: PMC5941775.