Taking a dip in cold water may cut 'bad' body fat in men and reduce the risk of disorders such as diabetes, suggests a major scientific review, but the new research was overall inconclusive on the health benefits the practice purportedly offers.
Swimming or immersion in cold water has become increasingly popular worldwide with advocates for the hobby trumpeting its supposed health benefits, including weight loss, increased libido and improved mental wellbeing. This activity can take many forms, including swimming in cold water during the winter; others are proponents of ice baths.
But taking the plunge may not reap the reported rewards, according to the new research, with a review by Norwegian scientists being inconclusive overall as to whether cold-water bathing offers any of its widely touted health benefits.
To conduct their research, the authors analysed 104 previous studies that demonstrated significant effects from swimming in cold water. Although their review was inconclusive overall, the authors noted that many of the previous studies had found there were health benefits to cold-water bathing, including weight loss. The studies found the activity had positive effects on 'good' brown fat, which helps burn calories, as well as on 'bad' white fat, which may protect against obesity and cardiovascular disease.
However, whether these effects are beneficial for our health, or indeed caused by the cold water, is tricky to assess, the scientists said. They noted that many of the purported health benefits may not actually arise from taking regular polar plunges, but simply from cold water swimmers' otherwise active lifestyles - including training to handle stress, active social lives, and positive dispositions. Essentially, it's unclear whether or not those who choose to swim during the colder months are naturally just healthier people.
"From this review, it is clear there is increasing scientific support that voluntary exposure to cold water may have some beneficial health effects," said lead author James Mercer, a professor in the Cardiovascular Research Group at UiT's Faculty of Health Sciences.
"Many of the studies demonstrated significant effects of cold-water immersion on various physiological and biochemical parameters. But the question as to whether these are beneficial or not for health is difficult to assess.
"Based on the results from this review, many of the health benefits claimed from regular cold exposure may not be causal. Instead, they may be explained by other factors including an active lifestyle, trained stress handling, social interactions, as well as a positive mindset.
"Without further conclusive studies, the topic will continue to be a subject of debate."
Published in the peer-reviewed International Journal of Circumpolar Health, the scientists - from UiT The Arctic University of Norway and the University Hospital of North Norway - noted that much of the available research they reviewed involved small numbers of participants, often of one gender, and with differences in water temperature and salt composition.
The main aim of the review was to determine whether voluntary exposure to cold water offered benefits for human health. The methodology involved a detailed search of the scientific literature. Excluded from the review were studies where participants wore wetsuits, accidental cold-water immersion, and water temperatures greater than 20 degrees centigrade. Themes covered by the studies that were eligible for review included inflammation, adipose tissue, blood circulation, immune system, and oxidative stress.
The review provided insights into positive links between cold water swimming and brown adipose tissue (BAT), a type of 'good' body fat that is activated by cold. BAT burns calories to maintain body temperature unlike 'bad' white fat which stores energy.
Cold exposure in water – or air – appears also to increase the production of adiponectin by adipose tissue. This protein plays a key role in protecting against insulin resistance, diabetes and other diseases.
Repeated cold-water immersions during the winter months significantly increased insulin sensitivity and decreased insulin concentrations, according to the review. This was for both inexperienced and experienced swimmers.
However, the authors pointed out that the profile of swimmers participating in the studies did vary. They ranged from elite swimmers or established cold-water bathers to those with no previous experience. Others were not strictly ice bathers but used cold-water immersion as a treatment post-exercise.
Education is also needed on the health risks associated with taking a dip in icy water, said the authors. These include the consequences of hypothermia, and of heart and lung issues which are often related to the shock from the cold. Immersion in cold water has a major impact on the body and triggers a shock response, such as an elevated heart rate.
