Immersion in cold water can reduce “bad” body fat in men and reduce the risk of diseases such as diabetes, suggests a major scientific review published in the peer-reviewed journal International Journal of Circumpolar Health.
The authors say many of the 104 studies they analyzed showed significant effects of cold water swimming, including on the “good” fats that help burn calories. This can protect against obesity, cardiovascular disease, they add.
However, the review was generally inconclusive about the health benefits of cold water bathing, an increasingly popular hobby.
Much of the available research involves small numbers of participants, often of the same gender and with differences in water temperature and salt composition. It is also unclear whether winter swimmers are naturally healthier or not, says the scientific expert team of review authors from UiT The Arctic University of Norway and the University Hospital of North Norway.
“It is clear from this review that there is growing scientific support that voluntary exposure to cold water may have some beneficial health effects,” said lead author James Mercer of UiT.
“Many studies have demonstrated significant effects of cold water immersion on various physiological and biochemical parameters. But the question of whether they are beneficial or not for health is difficult to assess.
“Based on the results of this review, many of the health benefits claimed for regular cold exposure may not be causal. Instead, they may be explained by other factors, including an active lifestyle, trained stress management, social interactions, and a positive mindset.
“Without further conclusive studies, the topic will continue to be a matter of debate.”
Weight loss, better mental health and increased libido are among the many health and well-being claims made by regular cold water immersion followers or anecdotal.
This activity takes many forms, such as swimming in cold water in winter, and is the subject of increasing interest worldwide.
The main aim of the review was to determine whether voluntary exposure to cold water has health consequences in humans. The methodology included a detailed search of the scientific literature.
Studies where participants wore wetsuits, accidental immersion in cold water and water temperatures above 20 degrees Celsius were excluded from the review.
Topics covered by studies eligible for review included inflammation, adipose tissue, circulation, immune system, and oxidative stress.
Immersion in cold water has a great impact on the body and causes a shock response, such as an increased heart rate.
Some studies provide evidence that cardiovascular risk factors actually improve in cold-acclimated swimmers. However, other studies have shown that the workload on the heart is still increased.
The review provided insight into the 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.
Exposure to cold water – or air – also appears 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 immersions in cold water during the winter months significantly increase insulin sensitivity and decrease insulin concentrations, according to the review. This was for both novice and experienced swimmers.
However, the authors point out that the profile of swimmers participating in the studies varied. They ranged from elite swimmers or established winter bathers to those with no previous winter swimming experience.
Others were not strict ice bathers, but used cold water immersion as post-treatment exercise.
Education about the health risks associated with ice water immersion is also needed, the authors say. These include the consequences of hypothermia and heart and lung problems that are often associated with cold shock.