A comprehensive overview of the sauna, its benefits and biological processes that occur when we go into the sauna.

Questions

What are the benefits of Sauna? What occurs biologically when we use the sauna to produce such benefits?

This short article will answer the questions listed, there will be scientific language used, but the aim is for everyone to understand, and come away with more knowledge on the sauna

History of the sauna

The famous Finnish sauna, is a room that is designed for users to experience, wet or dry heat sessions, the sauna temperature ranges from around 65°C - 90°C. The sauna was invented over 2,000 years ago by the Finns. Back then, the saunas were made of wood logs, and they used smoke and fire to create the heated cabin. The Sauna, or the "suavu sauna" as it was called back then, was a place of relaxation and cleansing for the Finns. Now, in the modern day, although technology has improved significantly, the theme is still the same. The modern-day sauna is a place for relaxation and stress relief.

At a temperature of 65°C - 90°C, most would assume you're going to sweat. Well, it turns out you do sweat... a lot, it is not uncommon to lose up to a 500ml of sweat after 10 minutes in the sauna, and sweating therapy has been around for a while now. Ancient Mayans were also using sweat therapy up to 3000 years ago.

Benefits of the Sauna

• Heart health improvements

• may help reduce the effects of asthma

• brain health improvements

• pain relief

• relaxation

• Toxin removal

Research studies

Heart health

Laukkanen et al. reported from a large European study that men who attended a sauna bathing session two–three times per week reduced their cardiovascular mortality rates by 30% and men who attended a sauna session four or more times per week reduced their risk by 50%, Similarly, Zaccardi et al. observed that men who attended a sauna bathing session two–three times per week reduced their risk for hypertension (high blood pressure) by 25% and men who attended a sauna session four or more times per week reduced their risk by 45% - Source (The Cardiometabolic Health Benefits of Sauna Exposure in Individuals with High-Stress Occupations. A Mechanistic Review, O'neal. E et al 2021).

Lung health

Other research studies that looked at the sauna and lung function showed: Twelve patients with obstructive pulmonary disease who took part in a sauna study, showed improved lung function and studies by Ernst et al a suggest that regular sauna bathing may reduce the incidence of respiratory infections.

Brain health

Finally, In 2016, researchers from Finland published findings of a 20-year study that linked sauna use with a lower risk of dementia and Alzheimers disease. The study involved 2,315 healthy men aged from 42 to 60 years. Those who used a sauna 2 to 3 times per week were 22 percent less likely to get dementia and 20 percent less likely to get Alzheimer’s than those who did not use a sauna. Those who used a sauna four to seven times a week were 66 percent less likely to get dementia and 65 percent less likely to get Alzheimer’s than those who used a sauna once a week. - source (what are the benefits and risks of sauna, Sara Lindberg 2022)

How do these benefits occur on a biological level?

There are two different types of stressors, there is acute stress and chronic stress, when you go into a sauna for 10-15 minutes, the heat acts as an acute stressor on your body. Acute stress is generally beneficial, as acute stress exposure upregulates mitochondrial adaptations such as mitochondrial fusion and mitochondrial biogenesis, resulting in a more robust intracellular antioxidant system. Additionally, the acute activation of the autonomic nervous system increases the release of glucocorticoids and catecholamines which are hormones released in the presence of physical stress. Glucocorticoids and catecholamines alter your metabolic rate and increase the activity of transcription factors that increase protein synthesis (thus more muscle mass or heat tolerance). Over time, repeated exposure to acute stressors will result in an overall stronger version of you, as a new physiological state or equilibrium is achieved through a process known as heterostasis. When we go into the sauna, the acute stressor of heat send us into the non-dangerous mild hyperthermia (an elevation of core body temperature). This results in redistribution of blood toward the skin to promote sweating to cool us down and the removal of waste products such as carbon dioxide and sodium as well as water. All of this creates a rise in blood pressure, heart rate and cardiac output. Thus, the effects of the sauna are mimetic to moderate exercise.

Continuing with the example of a sauna, tolerance to heat increases due to healthier mitochondria. We get healthier mitochondria because the heat stress increasing the expression of 5'-AMP-activated protein kinase (AMPK) in all cells including mitochondrial cells. AMPK acts as a cellular energy sensor, capable of detecting changes in the AMP/ATP ratio. When ATP levels decrease, AMPK activity increases, which subsequently upregulates metabolic pathways, such as glycogenolysis and lipolysis, to restore energy availability to cells. it is important to note that when do exercise or sauna therapy ATP levels are depleted. AMPK also shows the ability to modulate glucose in the blood which leads to better insulin sensitivity, which reduces the risk diabetes or obesity.

When we get into the sauna, the heat exposure also triggers the release of the interleukin-6 in the body. an anti-inflammatory cytokine, interleukin-6 also has some pro-inflammatory properties, but it is also anti-inflammatory because it triggers the release of interleukin-10, interleukin-10 is an important cytokine in the healing process of the body as it inhibits the production of pro-inflammatory cytokine such as C-reactive protein (CRP). CRP is considered one of the strongest markers of inflammation in the body, and an elevation in CRP plasma levels correlates strongly with the risk of future adverse cardiovascular events.