Cold showers are rarely the most tempting way to get clean, ranking only slightly above a cold bath for many people. But findings from a new 12 week experiment suggest the chilly routine may come with benefits that make it worth considering.

Choosing cold water also has an obvious budget advantage because it avoids the energy needed to heat a shower. For many households, however, a cold shower remains something endured only when the boiler breaks or hot water is unavailable.

Researchers from the University of Basel in Switzerland focused on cold showers while examining what might encourage people to adopt simple ways of reducing their environmental impact. The research has not yet undergone peer review, and its preprint is posted on the university website.

The team recruited 719 healthy participants between the ages of 18 and 65. None were already taking cold showers voluntarily, and each was asked to use water as cold as their plumbing allowed for 12 weeks.

Quite a few participants abandoned the experiment during its first two weeks. After that initial period, however, the dropout rate declined significantly, suggesting many of those who continued were able to maintain the routine.

“Our primary findings demonstrate that participants who take cold showers over the course of 12 weeks experience a significant reduction in illness days and sickness absence,” the team wrote. “Importantly, and contrary to widespread belief, participants who took cold showers were able to maintain this behavior throughout the study duration of 12 weeks.”

Compared with the control group, whose members continued showering normally, participants taking cold showers recorded 31% fewer days away from work because of illness. They also reported 26% fewer illness days, including days when they felt sick but did not necessarily miss work.

The cold shower volunteers also reported improvements in their physical and mental wellbeing, although those findings were less significant and were assessed through a questionnaire. The experiment was primarily designed to explore behavior change rather than provide an overall assessment of how cold showers affect health.

Even so, the findings were consistent with earlier research involving 3,018 participants in the Netherlands. That study found a 29% reduction in sickness absence among volunteers assigned to take cold showers, although it found no significant reduction in the number of days participants reported feeling sick.

Researchers in that earlier study attributed the difference to reduced symptom intensity, which may have allowed participants to manage their illness without missing work. The research also found that many participants appeared willing to continue their cold shower routines despite experiencing discomfort.

“Even though the vast majority of participants reported a variable degree of discomfort during cold exposure, the fact that 91% of participants reported the will to continue such routine (and 64% actually did) is perhaps the most indicative of any health or work benefit,” the team explained. “The most commonly reported beneficial effect was an increase in perceived energy levels (including many reported comparisons to the effect of caffeine).”

The new study also supported the idea that people may stick with a behavioral change when it offers both personal and environmental value. Researchers estimated that each participant reduced CO2 emissions by 15 kilograms (33 pounds) during the 12 week experiment.

That reduction was roughly equivalent to the emissions produced by driving 100 kilometers (62 miles). The calculation assumed that a typical five minute shower uses 45 litres of water that would otherwise need to be heated from 15°C to 40°C.

“When people see a personal benefit from changing their behavior and don't feel that they're giving something up or missing out, they're more motivated to stick with it,” Dr Lena Glaser, lead author on the study, explained. She added, “we need a more empathetic approach if we want people to change their behavior.”

Glaser also warned against forcing people to abandon every source of comfort or pleasure. “If we force ourselves to give up every comfort and pleasure, it will eventually take a toll on our well-being and mental health. And getting sick doesn't help the environment either,” she said.

For anyone intrigued by the results but not eager to endure an icy blast every morning, the routine does not need to be rigid. “The water doesn't have to be equally cold every day. We don't feel equally brave every day, and that's okay,” Glaser said.