“I didn’t even break a sweat” – says my husband disapprovingly when his workout doesn’t meet his intensity expectations. We’ve come to associate sweating with working hard, and many folks also believe that it helps us to detox – release harmful toxins that accumulate in our bodies from living in a polluted world. As a result some yoga teachers have adopted the attitude of “sweat them good” as an intention for their yoga classes, both to give their students a sense of working hard and to help them “detox”. So they crank up the external temperature and the intensity of the workout (both generate heat). Today we will take a closer look at those claims.
There is no shortage of articles and books on the subject of detoxification and it immediately becomes clear that there are two conflicting opinions on the subject. But first let’s take a closer look at the process of sweating.
There are two types of sweat glands in your body: eccrine and apocrine. Eccrine glands are located all over the body, their job is to regulate body temperature. It goes like this: your body temperature goes up (because of exercising or high external temperature) – your brain triggers your eccrine glands to produce moisture that shows up on your skin’s surface – moisture evaporates, cooling you down. (That is why if the environment is humid, the sweat doesn’t evaporate as well, the body doesn’t cool down as well, and you have higher risk of overheating and dehydrating). Apocrine glands exist only in certain areas of the body (like armpits and navel), they produce sweat in response to stress or stimulation.
According to most MDs, all sweat consists mostly of water, some sodium and chloride, a bit of potassium and a very small amount (less then 1%) of toxins. Because of that most doctors will tell you definitively – no, sweating does not help you release toxins. Toxins are mostly released through urine and feces, once the liver, kidneys and intestinal tract are done processing them.
Then there are natural medicine advocates that proclaim that “New research is revealing something remarkable about why the body sweats. Beyond its obvious role in regulating body temperature, sweating has been found to facilitate the elimination of accumulated heavy metals and petrochemicals, indicating that if we want to be healthy we should put regular effort into doing more sweating.” Those claims seem to hinge mostly on the work of Canadian scientist, Stephen Genuis, PhD and his team. In his articles Dr Genuis [don’t you love that name?!] states: “Toxic elements were found to differing degrees in each of blood, urine, and sweat. […] Many toxic elements appeared to be preferentially excreted through sweat.” His studies, along with other smaller studies, seem to point toward the conclusion that “Sweating offers potential and deserves consideration, to assist with removal of toxic elements from the body.” (See the summary of the research)
All the studies mentioned here are small (between 2 and 30 people), include much speculation and possess many limitations.
“Although authors described thorough precleaning methods, sweat concentrations measured in research settings are not well validated and varied according to the location on the body, collection method, and from day to day according to other variables such as hydration. Sweat contains metals not only from the blood plasma, but also evidently originating from dermal layers (particularly with significant dermal exposures, as for workers in welding, smelting, or battery manufacturing). It would appear that large variabilities in measured concentrations, apart from collection methods as mentioned above, were likely the result of differences in excretion amongst widely varying individuals with ranges of body burdens, genetic polymorphisms affecting detoxification efficiency, and physiological states, coupled with necessarily crude if simple experimental techniques. These variations were very much greater than would be expected due to limitations of analytical methods.”
This basically means that the results were all over the map – sweat concentrations varied greatly from day to day and from one body part to another; sweat contained metals from the skin’s surface; both concentration and detoxification efficiency varied widely from individual to individual. And we also have to remember that the amount of toxins was very, very small.
After analyzing the studies the authors state that “Undoubtedly further research in this area would improve understanding, but the available evidence suggests that physicians could consider recommending sweating as tolerated via exercise (preferred) and/or use of a sauna as a low-risk, potentially beneficial treatment for individuals who may be experiencing effects of toxic elements, or for individuals with regular exposure to or accretion of toxicants.”
Where does it leave us? It is possible that the traditional medical approach underestimates the potential benefit of sweating, and it is just as likely that the natural health-oriented community overestimates it.
Sweat does contain trace amounts of toxins, says Dr. Dee Anna Glaser, a professor of dermatology at St. Louis University and founding member of the International Hyperhidrosis Society, a medical group dedicated to the study and treatment of heavy sweating.
Sweating definitely won’t help clear the body of mercury or other metals, says Donald Smith, a professor of environmental toxicology at UC Santa Cruz, who studies treatments for metal poisoning. Almost all toxic metals in the body are excreted through urine or feces, he says. And less than 1% are lost through sweat.
Roger Clemens, director of an analytical laboratory at the University of Southern California that evaluates environmental toxins in the food supply says that the most efficient system for detoxification is the kidneys, liver, gastrointestinal tract and immune system. “Except when one of the major organs breaks down, there isn’t a medical device or any diet that can accelerate the body’s natural process of detoxification,” he says. Or any type of exercise, for that matter.
It seems possible to release a small amount of toxins via sweat during an intense physical activity. But you do not have any control over whether or not it will happen to you, which toxins get released and how much. And we certainly cannot say that specific activities and/or poses can facilitate that process. So if a yoga program claims to help you release toxins, it basically means that it will make you sweat by making you very, very hot. Anything beyond that is an overreach.
So does breaking a sweat indicate a more complete yoga practice? It depends on what you are after. I like to differentiate between the internal and external intensity. External intensity means dialing up the actual physical challenge of the practice, which will make you sweat and might give you a sense of accomplishment. Internal intensity means staying present with what you are doing, moving with your breath and using your yoga practice to gain deeper understanding of who you are. In my book, internal intensity is more important then external intensity. I can be sweating buckets in a yoga class and feel completely untouched. Or I can be doing very little movement but come out of my practice feeling more focused, vital and strong. You can certainly combine the two, if it is appropriate for your health, activity level, physical conditioning, and so on. We just need to be clear about our goals – are we after strictly physical benefits or do we want the full experience of what yoga has to offer?
Now back to detoxification. If it takes place in the kidneys and liver, is it possible to promote detoxification by “massaging” those organs, increasing the blood flow via certain poses? We will continue this conversation next week!