Finnish study finds 30-minute sauna session boosts immune defence

A new Finnish study suggests that a 30-minute sauna session may strengthen the immune system by increasing white blood cell counts, reports public broadcaster Yle. The findings have drawn global attention, with coverage from major outlets including the BBC, New York Times, Reuters, and CNN.

Researchers at the University of Eastern Finland, led by Professor Jari Laukkanen, found that sauna bathing triggers the release of white blood cells—key components of the body’s defence against disease—into the bloodstream. The study also observed changes in cytokine levels, signalling molecules that regulate immune responses.

The trial involved 50 participants who spent 30 minutes in a sauna, including a short cooling break. Blood samples were taken before, immediately after, and 30 minutes post-sauna. While white blood cell counts rose initially, they returned to baseline within half an hour.

“This suggests sauna bathing could benefit immune defence, though further research is needed,” Laukkanen said. He emphasised the need for longer-term studies on how repeated sauna use affects inflammation markers like white blood cells and cytokines over time.

Laukkanen’s team has conducted multiple studies on sauna health effects since the 2010s, linking frequent sauna use to reduced risks of dementia, stroke, and high blood pressure. Their work has sparked a global “sauna boom,” with Laukkanen noting his group’s research likely contributed to the trend.

The mechanisms behind sauna’s health benefits remain partially unclear. While heat-induced vascular expansion and contraction may improve blood vessel flexibility, Laukkanen suggests other factors—such as relaxation and mood enhancement—could also play a role in disease prevention.

“Sauna bathing is a holistic experience,” he said. “It’s harder to measure how it reduces stress, boosts wellbeing, or improves mood—but these factors may be significant in preventing various illnesses.”