Cold showers: what holds up and what doesn’t

The largest randomized trial of cold showers we know of took place in the Netherlands in early 2015. 3,018 adults aged 18 to 65, without serious illness and with no habit of cold showering, were randomly split into four groups. Three groups ended every shower with 30, 60 or 90 seconds of cold water for 30 days; the fourth showered as usual. After that, the shower groups could decide for themselves for another 60 days.¹

What came out

The cold showerers reported 29% fewer days off work sick. But there was no statistically clear difference from the control group in the number of days on which they felt ill. Whether people showered cold for 30, 60 or 90 seconds made no recognizable difference. There were no serious side effects from the showers; a lingering feeling of cold was common. At 90 days, 64% were still showering cold regularly.¹

The researchers point out the weaknesses themselves: participants knew which group they were in, all data came from online questionnaires, and about a fifth dropped out early. They cannot rule out a placebo effect.¹ Someone convinced that cold water toughens you up may be more likely to go to work with a cold. Whether that is healthy is another question.

What else is known

A 2022 review found 104 studies on voluntary exposure to cold water, such as winter swimming. Many showed measurable changes in the body. Cold appears to change fat tissue and improve the body’s response to insulin, for example. But most studies were small, often included only men or only women, and used different water temperatures. Whether winter swimmers are healthier because they swim, or healthier people are more likely to winter swim, is an open question.²

Careful after strength training

If you want to build muscle, skip the cold-water bath after training. In one study, 21 physically active men did strength training twice a week for 12 weeks. Half of them spent 10 minutes in cold water after each session; the other half recovered with light activity. Strength and muscle mass increased more in the group without cold.³ Our article on the minimum dose shows how little strength training is enough for your health.

Cold water can be dangerous

You can turn off a cold shower at any time. Cold open water is different: sudden immersion can lead to drowning, cardiac arrest and hypothermia. The evidence for the claimed benefits of cold water immersion also varies, and some rests only on anecdote.⁴