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“Detoxification” or “detox” for short has become a standard justification for all sorts of treatments that are not based on solid scientific principles or evidence. As we often refer to it – the “toxin gambit” is a marketing technique for scaring the public about the menace of unspecified toxins, then offering a treatment that will remove those vague and mysterious toxins. It is best not to reference specific amounts of specific toxins, because then they could be measured and the scam blown.

Any claim to detox, therefore, is a red flag for quackery. It is a hand-waving explanation to fill in the gaps of a lack of a plausible mechanism, along with antioxidant, or increasing oxygen (take your pick), increasing blood flow, boosts the immune system (or, alternatively, is anti-inflammatory) or at the extreme woo end of the spectrum, balancing your energy or harmonizing your vibrations.

In 2016 Jann Bellamy did a great job debunking the sauna detox claims. The idea here is that toxins come out in our sweat, so that if you sweat a lot in a hot sauna that will provide a nice deep detox. The problem with this claim is that it’s not true. More specifically, sweat releases an insignificant amount of substances that you would want removed from your body, like heavy metals, for example. If, for some reason, you had too much of these substances in your body and needed to remove them, don’t head for the sauna, head for your doctor’s office.

In fact, saunas can be counterproductive. The liver and kidneys are the primary organs evolved to remove toxins from the blood. By increasing your sweat you are actually decreasing the amount of urine produced and may in fact reduce toxin excretion. There is one potential exception to this, based on preliminary case-report level evidence – heavy metals like cadmium, lead, mercury, and arsenic. A 2011 review did find case reports of clinically relevant excretion of one or more of these heavy metals in sweat. This is not sufficient to justify sauna as a medical intervention, however. It is also not evidence for using sauna treatments to maintain health or routine “detox”.

The bottom line is that there is no evidence or rationale to think that sweating for the sake of sweating is good for you. But there are two further wrinkles I would like to explore. One is the evidence for health benefits from regularly using a sauna, independent of the sweating aspect, which I will deal with later. But first, now there are claims being made for infrared saunas.

One infrared sauna claims at the top of their website:

Sweating is good for you. Sweating is one of the body’s safest and most natural ways to heal and maintain good health. And that’s why every Sunlighten sauna is specifically designed to promote a deep, healthy and natural detoxifying sweat. Detoxification is important because it strengthens the body’s immune system and helps the body’s biochemical processes function efficiently so that we are better able to digest the nutrients in our foods.

This is all complete nonsense, but hits many of the marketing points for medical scams I listed above, throwing in that it’s “natural”. Promoters further claim that infrared detox (unlike regular saunas – I love how they throw older scams under the bus) mobilizes toxins from deep inside the tissue. The evidence for this claim: zero. The site has a single reference – to a promotional blog.

But this does get us to the broader claim – are there any health benefits (unrelated to detox) from regular use of saunas or specifically far-infrared saunas (FIRS)? Even mainstream sources will claim that there is some evidence for possible cardiovascular benefits. But let’s look at the state of the evidence, which is sparse.

A 2018 systematic review published in a CAM journal found:

Only 13 studies were randomized controlled trials and most studies were small (n < 40). Reported outcome measures were heterogeneous with most studies reporting beneficial health effects.

Small preliminary studies with heterogenous outcomes could describe any of hundreds of implausible therapies not likely to work, or that are later determined not to work by more rigorous testing. In other words, this level of evidence does not predict that a treatment will ultimately be found to work.

Most studies also do not report on side effects. While saunas are relatively safe, they are not risk-free. There are also case reports of sudden cardiac death while using a sauna, probably from dehydration. It is easy to get too overheated or dehydrated if not done properly. Everything in medicine is risk vs. benefit – you can’t just look at potential benefits and claim a treatment is worthwhile. What we are lacking with saunas, including FIRS, are the kinds of net health outcome studies that would be necessary to make a risk vs. benefit assessment.

Most of the mainstream attention is on the cardiovascular effects. Using a sauna does correlate with reduced blood pressure (in some, BP may also increase), increased heart rate, increased dermal perfusion with a reduction in organ perfusion, and increased left ventricular function and arterial flexibility. There are several problems with linking this evidence to alleged health benefits.

First – these effects are all short term, during the sauna and for 30 minutes following. We don’t know if there is any sustained change in cardiovascular function. Second, we don’t know that these changes are improvements. This relates to the third issue, it is possible that at least most of these changes may simply be due to dehydration. Reduced blood volume from water loss (similar to a diuretic effect) will reduce the blood pressure and increase the heart rate, relaxing blood vessels to increase perfusion. So perhaps all we are seeing is a transient effect of the dehydration that accompanies using a sauna.

What we need are longer-term studies and studies that follow net clinical outcomes. There is observational data, but this is highly problematic because it cannot be controlled.

At this point we can conclude that there is a thin rationale and little evidence to support sweating as a mechanism for detox. It is far better to allow the kidneys and liver to do their job. Saunas, both regular dry saunas and FIRS, result in short term changes to cardiovascular function, but there is no convincing evidence this is sustained or beneficial. In this latter case, more and better research is needed. Specific health claims are not justified, but if you choose to use a sauna for relaxation or because it feels good, remember to keep well-hydrated and keep the time limited.

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Posted by Steven Novella

Founder and currently Executive Editor of Science-Based Medicine Steven Novella, MD is an academic clinical neurologist at the Yale University School of Medicine. He is also the host and producer of the popular weekly science podcast, The Skeptics’ Guide to the Universe, and the author of the NeuroLogicaBlog, a daily blog that covers news and issues in neuroscience, but also general science, scientific skepticism, philosophy of science, critical thinking, and the intersection of science with the media and society. Dr. Novella also has produced two courses with The Great Courses, and published a book on critical thinking - also called The Skeptics Guide to the Universe.