There is evidence that cold water encourages the development of brown fat (which burns calories) and clearly, if you do a lot of swimming in cold water then you are going to burn your way through a lot of calories. But I suspect most of us will not stay in long enough for this to have a significant impact on our body mass.
As for boosting your immune system, the jury is still out. There have been plenty of animal studies, but few randomised human trials. One Dutch study published in 2016 in the journal PLOS One recruited 3,018 people and randomly allocated them to having a cold shower every morning for a month, or to a control group.
By chance, while the experiment was going on, 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. Even better, a 30-second blast of cold water gave the same benefits as sticking to it for longer.
But what about improving mood? Again, there’s not a huge amount of research or randomised trials, but there was a rather brutal study from 2000 where scientists looked at the impact of keeping young men in a tank of chilly water (14°C) for up to an hour.
Among other things they found that being in cold water increased their metabolic rate by 350 per cent and boosted levels of dopamine (a ‘feel-good chemical’) by 250 per cent.
There have, been some intriguing individual stories linking cold water swimming to improvements in mental health, like one published recently in the British Medical Journal. It looked at the case of a 24 year old woman called Sarah who had been taking antidepressants since the age of 17.
A couple of years ago she began a programme of weekly cold water swimming, which led to an instant improvement in her mood and in time she was able to come off medication.
Cold water therpay has been proven to increase endorphins, dopamine, brown fat burning capabilities, decrease in cortisol production and overall immunity. So whats stopping you from taking the plunge?