By Alex Fradera

Exposing your body to cold water has been promoted as a health tonic since at least the Roman period, so it’s about time we gave this a thorough investigation. In a new paper in PLOS One Geert Buijze and his colleagues report on the health and wellbeing effects of the “cool challenge” – a 30-day event in the Netherlands that involved more than 3000 people taking daily showers that ran cold for at least the last 30 seconds each time.

The clearest finding was a 29 per cent reduction in sickness absence for those who took cold showers compared with their colleagues who weren’t involved in the challenge; the length of the cold blast, whether 30 seconds or 90, didn’t matter. However cold showers didn’t provide an immunisation against sickness as such. The challenge participants felt ill as frequently as their colleagues, it’s just that somehow they were better able to fight through it and make it to work.

Most of the psychological factors that the researchers measured were not influenced by the chilly treatment. Participants reported a small increase in quality of life after 30 days, but that disappeared when re-measured later; meanwhile work productivity and levels of anxiety were unaffected. But the participants did report some other benefits such as higher energy levels, comparable to drinking a coffee, and over two thirds chose to continue the challenge for a further two months.

On this evidence, cold showers don’t refresh all the parts we might desire, but seem to insulate against the effects of illness and provide some yet to be determined energetic effects. Why? Maybe thanks to effects on the levels of hormones such as cortisol and norepinephrine, which respond in the short-term to a cold dousing. Or simply the benefit of a short daily physical activity – the power of a good shiver.

—The Effect of Cold Showering on Health and Work: A Randomized Controlled Trial

Alex Fradera (@alexfradera) is Contributing Writer at BPS Research Digest