‘Christmas Swim Anyone?’ - The Science behind the Cold

Feeling chilly? Sure it's good for ya! This year know what you're in for with the Christmas Swim...


On the lead up to Christmas Day there are always a few ideas that make their way around the dinner table and more often than not are discarded in the bin with a derisive laugh. An example might be a tentative ‘Can we do a vegetarian Christmas?’, the response being a quick-fired but absolute ‘Haha. Haha. Absolutely not.’ Another controversial one could be the question of the Caribbean Christmas. 

However, one idea that can sometimes garner a bit more contemplation is the ‘Are we doing the Christmas swim?’. Despite the obvious health implications in terms of risk of hypothermia (albeit small), to many the cold Christmas dip is alluring. As to why this is, aside from the weighty influence of communal comradery and tradition, science has recently indicated that the cold, with a dose of respect and moderation, is actually good for you. 

The Forty Foot in 2010 [Photocall Ireland]

To understand why this is we’ll turn to previous Science Gallery Dublin exhibitor, FAT artist Nuala Moore, who, so she’s told me, will be cheerily dipping a digit this Christmas near her hometown of Dingle, Co. Kerry. For those who haven’t heard of her Nuala is an amazing woman; she spends a large amount of time swimming at temperatures most of us would find impossible. She was part of a team of six swimmers who front-crawled their way around the Irish coastline (all 1,300km of it) in just 56 days. On top of that she holds a record that only seven other women can boast; she swam an icy kilometre at 0°C inside the Arctic Circle. She also swam as part of a relay team across the Bering Strait. It's no wonder then that she can respond to the cold water with a cheer and not the usual grimace, shiver, and retraction of said digit; she’s got to know the cold well. 

Training in cold waters can deliver salvation from the cold then, no surprise there. However, how this is possible is only just beginning to be understood, and the prime suspect responsible for this trainable, cold-enduring capacity is a little known tissue called Brown Adipose Tissue (BAT), or brown fat. Brown fat works by burning food to produce heat, via a special protein called UCP-1, rather than the cellular norm which is to burn food in order to produce a biochemical currency, known as ATP

Brown fat is very important for new born babies in order to keep warm, and also for hibernating animals such as brown bears; both of these startling creatures have ample stores of brown fat. It was thought that brown fat disappears entirely as we age, but this was recently found to be not true, and that adults actually keep stores of brown fat around our shoulders and necks (have you ever felt how warm it is up there?), and interestingly some people have more of brown fat than others.

Then earlier this year a study was published in the journal Diabetes that demonstrated that brown fat stores in healthy volunteers were plastic, and that the number of the heat producing cells increased directly with cold exposure. The study, authored by Dr. Paul Lee, provided an alternative night-home to five young men over the space of 4 months; they spent the nights (at least 10 hours) of their first month in a private room at an ambient 24°C, the second month at a nippy 19°C, the third at 24°C again, and the fourth at a cosy 27°C. 

The team monitored the subjects' brown fat stores at the end of each month by means of PET/CT and using the end-first month level as a control, found that by the end of the cold second month the subject’s brown fat levels had increased on average by 30-40%. These bumper brown fat stores returned to baseline at the end of the neutral third month, and were completely abolished by the month in the 27°C night-swelter. 

More so than simply producing more heat-generating brown fat cells, cells which hold a post that requires the burning of a lot of calories (something that should interest those struggling with excess weight), the team found that the month in the cold actually improved the men’s insulin sensitivity following a meal (i.e. cold exposure increased the amount of glucose absorbed from the bloodstream); a finding which should perk up the ears of those suffering with diabetes. 

However as with the majority of studies, this study is not without its limitations (the book ‘Bad Science’ by Ben Goldacre is highly recommended for clarification/identification of these), and the major drawbacks of this study are the low number of subjects (n=5), and the fact the subjects are young and healthy, which may muddy the metaphorical waters of the applicability of cold-exposure as a treatment for those suffering with obesity and diabetes. But still, these results are certainly promising. 

More than that, it joins other studies which are elucidating the potential healing properties of the cold; from the well documented preservation of organs for transplant to its use as a preventative for excess stroke damage, and now maybe to obesity and diabetes. The cold, if wielded correctly, could possibly be a powerful ally. 

But back to the question of the chilly Christmas swim, should you do it? As a once off; yes, yes you should, but for reasons of tradition and communal comradery and hot tea.* However if you make the decision to take up the cold-dip regularly, or simply turn down the thermostat at night, the implications for your health could likely be profound indeed. 

[* Some wise-words from Nuala on this; the cold is powerful, minimise the drinking the night before and get a good night’s sleep. Monitor your breathing and try to relax; your body will adjust if you give it a time. Keep an eye out for yourself and others around you, especially the Freddo-filled kids. Be prepared; bring two towels, sandwiches, headgear, gloves, and plenty of tay.] 


This blog post was written by James Morris, a member of our multi-talented Mediator Team here at Science Gallery Dublin. He can be found on Twitter at @JMorrisj6.


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