Sauna sessions of about 30 minutes may boost immune cell circulation

A Finnish study found that a 30-minute sauna session with a brief cooling shower midway led to a temporary increase in circulating neutrophils and lymphocytes, which returned to baseline after about 30 minutes.

A recent Finnish study found that a 30-minute sauna session with a cooling shower midway increased the circulation of certain white blood cells in participants. The study recorded spikes in neutrophils and lymphocytes during the session that returned to baseline after roughly 30 minutes. Lead authors suggested this pattern could reflect mobilization of immune cells from tissues into the bloodstream and their redeposition after the session. Sauna bathing and related contrast-therapy practices have long cultural roots in Finland and parts of northern Europe. Key findings: - Finnish researchers reported that a 30-minute sauna session, combined with a short cooling shower halfway through, increased counts of neutrophils and lymphocytes in the bloodstream. - The elevated white blood cell levels returned to normal about 30 minutes after the session ended. - The lead author, Ilkka Heinonen, said this may indicate movement of immune cells from storage sites into circulation where they can perform surveillance, followed by redeposition. - The article notes that other activities, such as exercise, similarly increase white blood cell circulation. - Observational studies have associated regular sauna use with various health outcomes, but they do not establish direct causation. Summary: The study suggests that a brief sauna session can temporarily mobilize immune cells into the bloodstream, which researchers describe as potentially beneficial for immune surveillance. Broader health effects and long-term implications remain undetermined at this time.