Should you take the (cold) plunge?

I love to try most things health related—in the interest of science, that is. Recently I went to a Nordic style spa. In case you do not know the theory, these spas offer variations on this theme: You spend about 20 minutes getting warm, either in a steam room or a dry sauna. Then you reluctantly sit in a very cold tub of water (8C) or drop a bucket of cold water over yourself. Following that, you relax in a comfy lounge chair at room temperature for a while then repeat the cycle. This cycle can be repeated at a relaxed pace about 2-3 times. As promised on the spa’s website, I certainly felt refreshed and invigorated after my time there. But are there any scientific benefits to this healthcare practice? Let’s start with stage one, getting warm. This can also be referred to as passive heat therapy. There is evidence to suggest that regular use of a passive heat therapy (aka sauna) can reduce the risk of developing many health conditions; from dementia/Alzheimer's, depression and CVD.1 There is more robust evidence for regular sauna use and the reduction of CVD mortality.2 One mechanism by which this works is through reduced blood pressure and improved flow-mediated dilatation.3 Much of this data comes from Nordic countries and Finland in particular, countries where people regularly incorporate saunas into their lifestyle. But I am more interested in the cold portion of this ritual. Mainly because my spouse wants to skip this step which she finds is actually physically painful. Perhaps we should define what this cold plunge is (or is not). This is not whole-body cryotherapy—which involves standing in an enclosed chamber while very cold air (-165C) is circulated for about 2-3 minutes. What we are discussing cold plunge or ice bath therapy. This involves jumping into a very cold bath of water and remaining there for as long as possible, around 2-8 minutes. Think: polar bear swim.Read: Beyond the heatThere is some evidence that Cold Water Immersion (CWI) can have positive effects on emotions.4 In this small study, 33 healthy adults did a CWI in 20C water for five minutes. Self-reported emotional states improved. Participants self-reported feeling more active, alert, proud, inspired and less nervous. Also interesting was that the brain activity of these same participants were measured with a fMRI machine. This showed an association with a temporal correlation across multiple neural networks. Another study showed similar results.5 In a small group of university undergrads, a single 20 minute CWI (13C) led to self-reported effects on mood compared to a control group. Reported health benefits include reduction in inflammation; however these claims might not be accurate. Several small studies have shown no reduction in inflammatory markers in athletes after CWI compared to active rest.6,7,8 However, CWI has been shown to improve recovery time in athletes.9,10 When you hear about the benefit of Cold Water Immersion, these are mainly based on regular and prolonged exposure, which can be demonstrated in regular cold water swimmers.11 Sadly, these benefits do not apply to my trips to the Nordic spa. However, if I were to take up regular swims in the ocean…Are there any risks to CWI? One author argues that the risk of “kill’ outweighs the “cure” potential of CWI.12 Those findings are based on risks of hypothermia, drowning and cardiovascular events. So should you go for an occasional cold plunge for your long term health? Probably not, but it does feel really good in the short term, as confirmed by one study that showed a 530% and 250% increase in plasma noradrenaline and dopamine concentrations after 14C CWI.13 REFERENCESLaukkanen JA, Kunutsor SK. 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