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In reply—Sauna Bathing and Healthy Sweating

      To the Editor:
      We thank Eiser and Brooks for their comments about the health benefits of sauna bathing. Regular sauna bathing has some beneficial effects on blood pressure, cardiometabolic biomarkers, arterial compliance, and cardiovascular function.
      • Laukkanen J.A.
      • Laukkanen T.
      • Kunutsor S.K.
      Cardiovascular and other health benefits of sauna bathing: a review of the evidence.
      Our prospective studies have shown that higher frequency and duration of sauna bathing are related to a lower risk of cardiovascular mortality, sudden cardiac death, stroke, hypertension, pulmonary diseases, and dementia.
      • Laukkanen J.A.
      • Laukkanen T.
      • Kunutsor S.K.
      Cardiovascular and other health benefits of sauna bathing: a review of the evidence.
      • Laukkanen T.
      • Khan H.
      • Zaccardi F.
      • Laukkanen J.A.
      Association between sauna bathing and fatal cardiovascular and all-cause mortality events.
      • Kunutsor S.K.
      • Khan H.
      • Zaccardi F.
      • Laukkanen T.
      • Willeit P.
      • Laukkanen J.A.
      Sauna bathing reduces the risk of stroke in Finnish men and women: a prospective cohort study.
      The feelings of relaxation and promotion of mental health and well-being associated with sauna sessions might be linked to the increased production of circulating levels of hormones such as endorphins.
      • Laukkanen J.A.
      • Laukkanen T.
      • Kunutsor S.K.
      Cardiovascular and other health benefits of sauna bathing: a review of the evidence.
      We have also reported an inverse association of frequency of sauna with several inflammatory markers, suggesting that the beneficial effect of sauna bathing on disease outcomes may in part be mediated via reduced inflammation.
      • Kunutsor S.K.
      • Laukkanen T.
      • Laukkanen J.A.
      Longitudinal associations of sauna bathing with inflammation and oxidative stress: the KIHD prospective cohort study.
      The inverse associations between sauna bathing and adverse outcomes have persisted despite adjustments for socioeconomic status and physical activity, which are potential surrogate markers of healthy lifestyles.
      In the typical warm and relatively dry Finnish sauna, skin blood flow usually increases from 5% to 10%, leading to a higher cardiac output, whereas blood flow to internal organs decreases with an increased body temperature. Sweat is secreted at a rate of 0.6 to 1.0 kg per hour at 80°C to 90°C temperature (176°F to 194°F, respectively), with an average total secretion of 0.5 kg, during a warm sauna bathing session.
      • Laukkanen J.A.
      • Laukkanen T.
      • Kunutsor S.K.
      Cardiovascular and other health benefits of sauna bathing: a review of the evidence.
      Sweat is known to contain solutes that accumulate in patients with renal failure.
      • Hanafusa N.
      • Lodebo B.T.
      • Shah A.
      • Kopple J.D.
      Is there a role for diaphoresis therapy for advanced chronic kidney disease patients?.
      Intensive sweating, induced by heat treatment with saunas (dry heat) or hot baths (wet heat), can increase loss of water, urea, sodium, potassium, chloride, lactate, and possibly other solutes.
      • Hanafusa N.
      • Lodebo B.T.
      • Shah A.
      • Kopple J.D.
      Is there a role for diaphoresis therapy for advanced chronic kidney disease patients?.
      However, although possible, it is not known how effective diaphoresis therapy might be in removing uremic toxins and if sauna bathing helps to get rid of toxins, as the liver and kidneys usually remove more toxins than sweat glands. It is also unclear whether the minuscule amount of toxins in sweat actually indicates a health concern. In addition, the concentrations of metals or other toxins detected in sweat are quite low. Whether sauna bathing will be a useful strategy for the elimination of toxins, including organochlorinated pesticides, from the body is a topic for further investigation. Indeed, randomized controlled trials are needed to further explore the potential health effects of sauna bathing.
      Sauna is a potential novel tool to promote public health in addition to many other previously known means, being an enjoyable way to take care of general health and well-being among many people; but its effectiveness and safety as an additional diaphoretic or diuretic therapy need to be carefully investigated. Sauna bathing may be a remedy to the call for additional lifestyle interventions needed to enhance both general health and wellness, possibly in populations that have difficulty exercising, and at least as an adjunct to exercise training. Most people usually tolerate a typical warm dry sauna, which is a pleasurable activity with potential health benefits. Overall, we warmly recommend taking sauna bath as part of a healthy lifestyle for the prevention of chronic diseases.

      References

        • Laukkanen J.A.
        • Laukkanen T.
        • Kunutsor S.K.
        Cardiovascular and other health benefits of sauna bathing: a review of the evidence.
        Mayo Clin Proc. 2018; 93: 1111-1121
        • Laukkanen T.
        • Khan H.
        • Zaccardi F.
        • Laukkanen J.A.
        Association between sauna bathing and fatal cardiovascular and all-cause mortality events.
        JAMA Intern Med. 2015; 175: 542-548
        • Kunutsor S.K.
        • Khan H.
        • Zaccardi F.
        • Laukkanen T.
        • Willeit P.
        • Laukkanen J.A.
        Sauna bathing reduces the risk of stroke in Finnish men and women: a prospective cohort study.
        Neurology. 2018; 90: e1937-e1944
        • Kunutsor S.K.
        • Laukkanen T.
        • Laukkanen J.A.
        Longitudinal associations of sauna bathing with inflammation and oxidative stress: the KIHD prospective cohort study.
        Ann Med. 2018; 50: 437-442
        • Hanafusa N.
        • Lodebo B.T.
        • Shah A.
        • Kopple J.D.
        Is there a role for diaphoresis therapy for advanced chronic kidney disease patients?.
        J Ren Nutr. 2017; 27: 295-302

      Linked Article

      • Cardiovascular and Other Health Benefits of Sauna Bathing: A Review of the Evidence
        Mayo Clinic ProceedingsVol. 93Issue 8
        • In Brief
          Sauna bathing, an activity that has been a tradition in Finland for thousands of years and mainly used for the purposes of pleasure and relaxation, is becoming increasingly popular in many other populations. Emerging evidence suggests that beyond its use for pleasure, sauna bathing may be linked to several health benefits, which include reduction in the risk of vascular diseases such as high blood pressure, cardiovascular disease, and neurocognitive diseases; nonvascular conditions such as pulmonary diseases; mortality; as well as amelioration of conditions such as arthritis, headache, and flu.
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      • Effect of the Significant Loss of Salt in Sweat
        Mayo Clinic ProceedingsVol. 94Issue 4
        • In Brief
          The review article on the health benefits of sauna bathing in the August 2018 issue1 appeared comprehensive but failed to mention the effect of the significant loss of salt in sweat that occurs with this clearly beneficial event repeated on a regular basis. Wouldn't most— if not all—of these benefits occur simply as a result of regularly repeated substantial losses of salt from the body? Is this counter-balanced by the consumption of salt-preserved fish in Finland?
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      • Sauna Bathing and Healthy Sweating: II
        Mayo Clinic ProceedingsVol. 94Issue 4
        • In Brief
          In their review on Cardiovascular and Other Benefits of Sauna Bathing, Laukkanen et al1 observed that, in a previous population cohort study, they detected that frequent use of sauna bathing (4 to 7 times a week), showed a 66% reduction in dementia in Finnish men compared with those who had 1 session per week. Regarding a possible mechanism for such a dramatic effect, toxicologists have shown that sweating is a major means of excreting both organochlorine pesticides2 and a variety of toxic metals including cadmium, lead, and aluminum.
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