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What Happens in Our Body in a Sauna


Sauna bathing can be considered an exemplary biohack. By modulating the temperature of our environment, we have the power to influence the biochemical and physiological processes in our body, and we will feel the effects on our psyche as well. In this article we will explore what happens in the body during sauna bathing. And to make things even more interesting, we will go through one such sauna ritual together. Let’s get started.

Phase I: Heat

We have already showered and are now entering the sauna room. We settle ourselves comfortably on the rather uncomfortable wooden benches. After a few minutes, our capillaries begin to dilate. Through them, blood rushes to our extremities and closer to the body surface. That is the moment when your sauna companion tells you that you look like a lobster. The sympathetic nervous system is activated and our heart rate quickens [1]. The blood flowing through our sophisticated network of blood vessels sets out on a detoxifying mission to capture metabolic waste, such as lactic acid, heavy metals, and toxins. Metabolic waste is formed in the body naturally as a byproduct of metabolic processes or physical exercise (lactic acid). Breathe in. Breathe out. Try to focus only on breathing. Our sole purpose now is to relax completely.


At this moment, certain (welcome) guests enter the scene. Beta-endorphins and dynorphins. Dynorphins are something like the counterparts of endorphins. While endorphins usually bring about feelings of well-being, dynorphins make themselves known in moments of discomfort, whether it is more strenuous exercise, or exposure to extreme temperatures [2, 3]. So it is dynorphins that are responsible for our initial unpleasant feelings during sauna bathing. They are welcome, nonetheless, because they make our cells more receptive to the beta-endorphins that come later. Beta-endorphins are naturally occurring opioids which our body produces as a part of a pain-relieving strategy [4, 5]. They improve our mood and induce feelings of happiness. It is true euphoria caused by a self-produced inner opioid. Breathe in. Breathe out. Finally, we begin to acclimatise to the sauna. After a certain time (subjective to each individual) comes the right moment for the next step of the sauna ceremony. Time for the other extreme. Cold.

Phase II: Cold

Whether you choose an ice cold shower, pool, lake, or snow, we are literally going from one extreme to another. At this point, our blood vessels constrict. The process is called vasoconstriction and our blood vessels start to pump blood from our extremities to the core [6]. Why? It is a preventive mechanism of the body when it limits circulation only to vital body parts. After all, we can do without a limb, and so priority is given to the vital organs found in the trunk and head at this moment. Although it may sound scary, don’t let it discourage you. It is for a good reason that in Finland, sauna is called a poor man’s medicine.


Breathe in, breathe out. We should not forget to consciously control our breathing. Intense cold caresses every last bit of our skin. Blood rushes to our core and there, internal organs take charge. The liver and kidneys filter our blood to a certain extent and strive to eliminate the aforementioned metabolic waste, heavy metals, and toxins. Dynorphins make themselves known again. Meanwhile, thoughts that usually swirl around in our head dissipate. How could they not? Our brain is focused only on the temperature shock to which we have exposed it. Does it feel comfortable? Does it feel uncomfortable? I admit that the line for the final decision is very fine. In any case, this is a singularly auspicious opportunity to instantly find yourself in the present moment, fully aware of your own body, your beating heart, and the rhythm of your breath. Breathe in, breathe out.

Phase III: Relaxation

Whether you repeat the cycle of heating up and cooling down several times or not, do not skip the final stay in a place at room temperature. This is an important part of the sauna ceremony. Give your body the opportunity to relax after the extreme temperatures. Our good friends, beta-endorphins, but also the famous dopamine will keep you company. These substances will help bring about a feeling of bliss and inner peace.

All in moderation, but through extreme temperatures to health

Heat shock proteins

At the beginning of this article I mentioned that by sauna bathing regularly, we can influence the biochemical processes in our body. Through sauna and the associated temperature changes, we activate numerous cellular reactions in the body. One of them is an increased production of heat shock proteins [8]. In this context we could think of heat shock proteins as a sort of internal guards and repairmen. Proteins found in our body require very specific folding and organisation in order to be active. Among other things, they serve a biochemical thermoregulatory function. They protect enzymes and proteins from damage caused by extreme temperatures [9]. At the same time they ensure and check if other proteins have proper conformation and folding. They are even able to unfold incorrectly folded proteins. Heat shock proteins also support the immune system by encouraging immune cells - white blood cells, such as macrophages and lymphocytes - to work [10]. 

Increasing the number of white blood cells

Studies show that regular sauna bathing promotes white blood cell production [11]. Do you remember the children’s series Once Upon a Time… Life [12]? In it, lymphocytes belonged to the flying patrol unit of the immune system. Lymphocytes are one of the subtypes of white blood cells and their realm is the bloodstream and extracellular matrix. They are excellent seekers capable of identifying and dealing with intruders or abnormal cells infected with a virus or damaged by stress [10]. Macrophages are the largest of white blood cells. They benefit us in many ways - for example, by regulating inflammation or eliminating foreign, non-functional, or dead cells in a process called phagocytosis. You may remember them from the series as yellow toad-like mobile objects. They performed phagocytosis by literally gobbling up intruders with their big mouths. 


Let’s finish by summing up the ways in which sauna represents a copybook biohack:

  • By practising sauna bathing regularly, we train our own biochemical processes

→ vasodilation and vasoconstriction, promoting the production of white blood cells and heat shock proteins

  • Positive effect on our physiological processes

→  improved organ function, better blood perfusion in organs and skin

  • Positive effect on our psyche

→ better resistance to stress, both physical and mental


If you want to know about the mental health benefits of sauna, don’t miss this article that Veronika wrote for you.


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[5] Kukkonen-Harjula, K., and K. Kauppinen. How the sauna affects the endocrine system Ann. Clin. Res. 20, no. 4 (1988): 262–66.



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