Heat Therapy and Your Immune System
Over time our bodies have adapted to respond to infection by rising the internal temperature (ie. spiking a fever). When your internal body temperature is raised it can strengthen your immune system by causing an increase in white blood cells, lymphocytes, neutrophils and improving the function of natural killer cells. Rising temperatures can also help your body to produce heat shock proteins (HSP) which can reduce the formation of inflammatory cytokines. HSPs increase the master antioxidant glutathione, helping to clear free radicals and inflammatory cellular debris. There is also evidence that HSPs (specifically HSP70) block viral ribonucleoprotein from being exported - therefore reducing an RNA virus's ability to replicate. Hyperthermia treatment has also been shown to increase Nitric Oxide (NO) formation in the body. Nitric oxide is a gas formed in the body which can result in vasodilation, which is why you may have heard of it in regards to hypertension (high blood pressure). There is research to support that NO prevents the entry of SARS-CoV (coronaviruses) into cells by preventing fusion of Spike proteins (S Protein) and Angiotensin Converting Enzyme (ACE) (Akerstrom). NO has also been shown to suppress the viral replication cycle of SARS-CoV (Akerstrom). From this we can conclude that mild temperature elevations may be helpful in fighting and preventing infections. So how does one take advantage of these benefits without having the active infection to cause higher temperatures? Hop in the sauna! Hyperthermia (rising one’s body temperature) can be achieved by exposing oneself to high temperatures at increasing temperatures and durations as tolerated. This can typically be achieved through a sauna, steam room or hot baths.
Hormesis is our body’s response to stressors. A small amount of stress (heat, cold, fasting, exercise) causes a slight damage response from the body, which allows it to adapt and compensate in the future, building resilience. Based on studies of Hyperthermia from Finland (the home of the Finnish sauna and where most of the research regarding heat therapy comes from) it is ideal to sit in a sauna at least 2-4 times a week for 15-30 minutes per session. The ideal temperature for sauna therapy is between 156-212F (based on tolerance - this can take time to work up to!). Also note that this temperature range is for a typical Finnish sauna (the type in your gym) while infrared saunas are often operated at a lower temperature due to deeper tissue penetration. Interestingly, sauna therapy has been studied as a possible defense against influenza since the late 1950s. One study of 2000 men found that those who partake in sauna 4 times per week were 41% less likely to have a respiratory disease and had a 47% reduced risk of pneumonia following respiratory infection (Kunustor). Another study found that the frequency and duration of the common cold was cut in half in individuals who had been regularly undergoing saunas (Ernst).
It is important that you move at your own comfort level, start with short sauna sessions and increase the duration as your body increases resistance. Be sure to hydrate well before and after using the sauna. Never use the sauna while under the influence of drugs, alcohol or other dehydrating substances. Consult with your doctor before you begin using the sauna to make sure that it is safe for you specifically.
Akerström S, Gunalan V, Keng CT, Tan YJ, Mirazimi A. Dual effect of nitric oxide on SARS-CoV replication: viral RNA production and palmitoylation of the S protein are affected. Virology. 2009 Dec 5;395(1):1-9. doi: 10.1016/j.virol.2009.09.007. Epub 2009 Oct 1. PMID: 19800091; PMCID: PMC7111989.
Ernst E, Pecho E, Wirz P, Saradeth T. Regular sauna bathing and the incidence of common colds. Ann Med. 1990;22(4):225-7. doi: 10.3109/07853899009148930. PMID: 2248758.
Kunutsor SK, Laukkanen T, Laukkanen JA. Sauna bathing reduces the risk of respiratory diseases: a long-term prospective cohort study. Eur J Epidemiol. 2017 Dec;32(12):1107-1111. doi: 10.1007/s10654-017-0311-6. Epub 2017 Sep 13. PMID: 28905164.
Kunutsor SK, Laukkanen T, Laukkanen JA. Frequent sauna bathing may reduce the risk of pneumonia in middle-aged Caucasian men: The KIHD prospective cohort study. Respir Med. 2017 Nov;132:161-163. doi: 10.1016/j.rmed.2017.10.018. Epub 2017 Oct 23. PMID: 29229091.