Dr Michael Mosley

Dr Michael Mosley: How cold showers could boost your immune system

There is mounting evidence that braving an icy shower in the morning could keep illness at bay and may even help your brain stay sharp. Brrrrrr!

Recently, I made a 10-part BBC Radio 4 podcast called Just One Thing where in each 15-minute episode I explored the science behind simple things you can add to your daily routine, like squats, eating more fermented food or going for brisk, early morning walks.

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It was an instant hit and was immediately recommissioned. You can find the original series on BBC Sounds, where you will also find the latest episodes of the second series.

One of the most popular episodes from the first series explored the risks and benefits of cold water immersion. For this episode I started having cold showers every morning, starting with a brief burst of hot water, followed by 45 seconds or so of an icy cold blast.

It certainly perks you up, but is there anything more to it than that? Well, there was a Dutch study published in 2016 in the journal PLOS One where they recruited 3,018 people online and then randomly allocated them to having a cold shower every morning for a month, or to a control group who continued as normal. Those having the cold shower were further divided into those asked to do it for 30 seconds, 60 seconds or 90 seconds.

Over the following winter there was an outbreak of flu and it turned out that those people having cold showers were 30 per cent less likely to take time off for sickness than those in a control group, though it didn’t matter whether you were in the 30-second group or either of the longer groups.

As for improving mental health, there haven’t been any shower-related studies I could find, and even the cold water swimming claims rely more on anecdote and case studies than strict randomised controlled trials.

Illustration of a person taking a cold shower © Joe Waldron
© Joe Waldron

That said, researchers from Cambridge University appear to have found a mechanism. A few years ago they identified a ‘cold-shock’ protein called RBM3, which in mice rises in response to sudden cooling and seems to be important for creating new connections between neurons in the brain. More recently, they found higher levels of RBM3 in the blood of regular cold water swimmers.

If you like the idea of cold water swimming during the coming months, do be cautious and go with a friend or join a club. A few years ago I was out swimming with my wife, Clare, when suddenly everything went black. A few hours later, I came to in hospital. Clare said I had swum to the shore and then looked around blankly, with no idea where I was.

It turns out I’d experienced something called ‘transient global amnesia’, brought on by the cold water. Thankfully it soon passed and the consultant said it was unlikely I would experience it again. Nonetheless, come the end of September I will stop outdoor swimming, but continue with the cold showers.

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