Studies: Sauna and Cold Showers May Boost Immunity and Reduce Sick Days
Finnish researchers found that 30 minutes in a sauna temporarily raises white blood cell counts in the bloodstream. A Swiss study found that people who regularly take cold showers missed 26% fewer workdays due to illness.
Ahead of the flu season, scientists have published two studies related to immunity: one carried out in Finland on the effects of the sauna, the other in Switzerland on cold showers. Both suggest that temperature extremes may benefit health.
Sauna activates immune cells
Finnish researchers at the University of Turku examined the effect of the traditional Finnish sauna on the body. The reason was that scientific research on the sauna's effects has been fairly limited, even though many Finns are convinced of its restorative power.
The experiment involved 51 middle-aged participants. After 30 minutes in a sauna with dry air at around 70 degrees, the number of white blood cells in their bloodstream rose significantly. These cells help protect the body against pathogens. The counts of the fastest-reacting neutrophils and of lymphocytes rose, as did monocytes, eosinophils and basophils. Levels of cytokines, the immune system's signalling proteins, changed only slightly on average.
Exercise researcher Ilkka Heinonen wrote in the journal Temperature that the sauna appears to mobilise extra white blood cells from tissues into the bloodstream, and that they return to the tissues after the session. In his view, this periodic influx is useful because the cells can patrol the body more effectively.
The effect was short-lived: within 30 minutes most changes had disappeared, with only a few monocytes remaining. The immune response is therefore activated during the sauna visit but gives no lasting advantage. White blood cell counts also rise after physical exercise.
Cold showers and fewer sick days
Lena Glaser, a psychologist at the University of Basel, studied how cold water affects people and which psychological factors encourage them to adopt uncomfortable habits. She analysed the illness records of 719 Swiss residents. People who regularly took cold showers missed 26% fewer workdays due to illness than those who used only warm water. Cold-shower fans also reported slightly better psychological well-being. The results were published in the Journal of Health Psychology.
