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10. Sauna effects on athletic endurance and recovery >>

Reading time: approx 6 min 

3. Sauna and detoxification

Humans sweat for one reason only, to dump the heat load. Is detoxification a by-product of this function? Let's find out!

 

"Do you think they clean the walls in this sauna often enough?" one of the three friends who had just sat down in the sauna asked, somewhat anxiously. "I hope so; otherwise, there could be toxins all over the walls," replied one of the others.

And the conversation continued in the direction of detoxification and its importance. They explained that they don't clean the walls very often in some public saunas, so toxic substances are present. I admit that I wanted to engage in a conversation at some point, but I took the opportunity to be quiet. That way, I could learn more about some so-called bro-science*, I thought.

* Bro-science - The Urban Dictionary says that bro-science is a term for misinformation circulated among men, usually claims among fitness enthusiasts not backed by science. 

The story continued as in an advertising brochure. It went something like this: "In the last century, with the development of the oil industry, industrial agriculture and consequently with industrial food, pesticides, cleaners, beauty products, synthetic clothing, medicines and many other products, we have begun to introduce many new substances into the body. The body doesn't know what to do with them. That is why it can't get rid of them quickly enough through regular detoxification pathways, so it usually stores them in fat cells, which act as a buffer to protect other organs from toxins. Sounds interesting and common sense able, I thought. Then followed: "Sweating in the sauna removes these toxins from fat cells. As a result, toxins accumulate on the walls of public saunas, so regular cleaning of the walls is important." At this point, I had to bite my tongue, honestly.

Admittedly, such and similar detox stories are quite logically composed, intuitive, easy to read or hear, and consequently sell well. They remind me of the story of intermittent fasting. It is often possible to listen to the explanation that it is wise and healthy to avoid breakfast because it prolongs the night's fast or does not interrupt it. 

That this is indeed the case is supposedly confirmed by the very word breakfast, as it derives from the interruption of fasting. (Break-fast - how convenient.)

What particularly fascinates me about this story is that it isn't used only by so-called bro-scientists but by some scholars who have professional literature at their fingertips. 

But science is evident. Our metabolic capacity and our cells' sensitivity to insulin are higher in the morning than in the evening. In other words, if we eat two identical meals, one in the morning and the other in the evening, the evening's one will show up on the scale more. (1,2) Besides, the night is for rest. Not only for the muscles and the brain but also the digestive organs. So, it would make a lot more sense to skip dinner than breakfast. This often does not coincide with big dinners' custom or culture, which prevail in the Western world and many places in Asia. So, the story of breakfast is very convenient, although contrary to the facts, which, obviously, does not bother the narrators. 

After all, our grandmothers were right when they claimed that it is wise to have breakfast like a king, lunch like a prince, and dinner like a beggar.

And if we go back to detox, various treatments and programmes promise "deep" cleansing of toxins through sweating. In doing so, they "forget" to explain what science has to say about it, so let me try to make up for it at this point.

Firstly, something to warm up. Linguistically, toxins are toxic substances, small molecules, peptides or proteins produced in living cells or organisms, so synthetic poisons created by artificial processes do not fall into the category of toxins. Not to be accused of trifling, I will continue to ignore this linguistic detail and consider both the toxins and other potentially harmful substances that sweat may contain.

If we want to understand the answer to the question of whether a sauna helps remove toxic substances from our body, we need to find out answers to 3 questions:
1. How does the system or process of eliminating toxins and other unwanted substances in the body works?
2. Where does sweat come from, and what does it consist of?
3. What do measurements and scientific research say on this topic?

 

1. Process of eliminating toxins and other unwanted substances

Let's take a brief look at the process of removing toxins and other unwanted substances in the body. As we know, metabolic processes constantly take place in cells. There is no life without them. By-products of these metabolic processes are various substances that are not very toxic, but if they accumulate, they can cause problems. Therefore, we regularly eliminate them in multiple ways. For example, ammonia and urea derive from the breakdown of proteins. An excess of ammonia in the blood (hyperammonemia) may lead to brain injury and death. (3,4) So homeostatic mechanisms must work correctly. And the elimination of ammonia through the known mechanism of urine excretion is a regular part of those mechanisms. We also recycle about two and a half million red blood cells every second. They produce bilirubin, the kind of waste that turns mud brown. Breathing produces carbon dioxide, which we get rid of by exhaling. Through food, respiration and skin, we also bring various substances that do not benefit us, and we would like to get rid of them. In doing so, we rely heavily on a sophisticated cleansing system represented by the liver and kidneys. The liver plays a decisive role in detoxification and represents a genuine chemical factory for decomposition. Toxic metabolic wastes are chemically modified and converted into less toxic substances. With powerful, versatile enzymes, they turn, say, pesticides or other harmful molecules into less harmful substances. Some liver waste is excreted in a fluid called bile. Other waste goes through the bloodstream into the kidneys, representing a kind of filtration system for the blood. The kidneys store nutrients and other beneficial molecules and excrete waste, such as broken-down molecules from the liver and excess hormones and other toxic substances in the urine. Their job is to maintain homeostasis (optimal level) of minerals, water and electrolytes in the blood. So, the liver and kidneys are the ones that take care of removing toxins and other harmful substances in the body. And if they are healthy, they do it very well. 

The idea that sweat is vital in eliminating toxins may stem from the fact that the sweat glands are, in fact, quite similar to the kidneys. Their microscopic structure and capabilities strongly suggest this notion. (5) Some experts, therefore, recommend thermally-stimulated sweating as an additional therapeutic regimen for renal patients. (6) One way to determine whether sweating may play a role in detoxification is to analyse its composition. 

2. Sweat composition

Sweat is a very complex aqueous mixture of chemicals, explains Lindsay B. Baker, PhD, in her extensive and in-depth article on sweating (7). Although mostly water and salt (NaCl), sweat also contains many other solutes in various concentrations. Most substances originate from the interstitial fluid (a part of the extracellular fluid between the cells), a precursor to sweat. So, we can conclude that sweat will contain the same substances as said liquid.

Measuring and analysing sweat composition is not as easy to do as it may seem at first glance. It is necessary to be very careful and use a valid methodology; otherwise, we may get very misleading results. What can happen quickly is that substances on the skin before sweat get into the measured composition. The liquid and residues collected from the surface of the skin may contain more than just sweat. Besides, thermal sweat secreted by the eccrine sweat gland also deposits sweat duct contents, sebum secretions (an oily, waxy substance produced by your body's sebaceous glands), the skin cells and other surface contaminants on the skin, including substances that entered the skin with potential contamination via steam in the sauna. Ignoring this fact can lead us to wildly inaccurate conclusions, explains Baker.

So, what can we expect or find in the sweat? In addition to water, there are a few other substances that we classify as micronutrients. Most are electrolytes, Na, Cl and K, and some vitamins and trace minerals, i.e. minimal amounts, and those that are not considered micronutrients. These include waste products of metabolism, proteins, amino acids and various toxic substances. (7) Given the established composition, one might conclude that sweat plays some role in the excretion of unwanted substances. However, if we look at the matter in a little more detail, things get a little more complicated.

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Note: In continuation, you can read more about this somewhat controversial topic and the excretion of toxic substances through sweat, about cases where the sauna has been successfully used clinically for detox, and whether the claim that the sauna supports detoxification processes is a fact or a myth.

Reading time: approx 6 min 

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10. Sauna effects on athletic endurance and recovery >>