Can Sitting in a Sauna Help Fight Infections?
Dr. James DiNicolantonio
Did you know that since 1957 sauna therapy has been used as a potential way to prevent the flu?  It’s true! During World War II, sauna therapy was even noted to prevent the spread of typhus fever in Finnish troops, “The main method of typhus prevention in Finland consisted of regular sauna bathing, which was culturally acceptable and very efficient.”  Since then, numerous studies have been published confirming that sauna therapy is indeed beneficial for fighting infections.[3,4]
For example, a clinical study divided 50 patients into two groups, one group of patients were assigned to sauna sessions over several months and the other group did not receive sauna therapy; can you guess what happened? The group that received sauna sessions had their incidence of the common cold cut in half.  And the benefits of sauna therapy don’t stop at the common cold. People who use saunas at least 4 times per week, compared to those who use the sauna once per week or less, have approximately half the risk of developing pneumonia or respiratory diseases. [5,6]
So how does going into a sauna help fight against infections? For one, our body’s first defense against infection is a fever. By boosting core body temperature, and mimicking a fever, sauna therapy may help our bodies fight off infections before they take hold. It’s not recommended to go into a sauna once you have a fever because at that point your body is doing sauna therapy on its own. However, the consistent use of a sauna may help reduce the ability of viruses to replicate in the body. [4-6] And this is important, especially early on in an infection, prior to it causing a fever, spreading to the lungs and taking a firm hold.
Going into the sauna causes hyperthermia or a rise in core body temperature. Essentially, sauna therapy is “heat shock” therapy. It shocks the body with heat and induces a short-term stress on the body. However, once the body has recovered from a sauna session it is more resilient to other stressors. This is known as hormesis. Basically, what doesn’t kill you makes you stronger (think of sunlight, exercise, or cold therapy). And in the case of sauna therapy we are talking about the immune system getting stronger.
We didn’t know exactly how saunas worked against viruses until recently. For example, when we go into a sauna our body increases the production of something called heat shock proteins (HSPs).  HSPs are released to prevent proteins from degenerating from heat shock or other stress.  They also help stimulate both our innate and adaptive immune system.  Thus, making our overall immune system more robust. Additionally, heat shock proteins can directly inhibit influenza viral replication [10-12] and make our cells more resistant to death from external stressors. [13, 14] In other words, the release of heat shock proteins with sauna therapy may, 1.) boost our immune system, 2.) inhibit viral replication and 3.) protect our immune and lung cells during cytokine storms. Talk about a triple combination punch!
The benefits of HSPs and sauna therapy on our immune system don’t stop there. Heat shock protein-70 can stimulate the release of nitric oxide from monocytes.  And nitric oxide can inhibit the replication of severe acute respiratory syndrome (SARS). [16 , 17 , 18] Additionally, sauna therapy boosts nitric oxide,  as it increases the expression of endothelial nitric oxide synthase (eNOS), which is the enzyme that makes nitric oxide in the body. [20, 21] Infrared sauna therapy stimulates eNOS above and beyond any thermal effect, suggesting that infrared saunas may have an advantage over traditional saunas.[20, 22, 23]
A 15-minute sauna session can also stimulate the immune system, increasing the number of white blood cells, lymphocytes, neutrophils and basophil counts.  Hyperthermia, as found with sauna therapy, also increases the antiviral effect of interferons. [25 , 26] Interferons are produced by our body to increase antiviral antibodies and to stimulate our immune system. Thus, there are many pathways for how sauna therapy may help us fight against infections.
Overall, sitting in a sauna for approximately 15-30 minutes per day, for 4 or more days per week, is a great way to increase heat shock proteins, activate the immune system and potentially inhibit viral replication. Clinical evidence in humans suggests that sauna therapy reduces the incidence of the common cold and may reduce the incidence of influenza, pneumonia and respiratory diseases.
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