Scientists lukewarm on the benefits of cold swimming
Even well into her ninth decade, American actress Katharine Hepburn used to take a daily dip in the chilly waters off the Connecticut coast, ostensibly to keep winter colds at bay.
Enthusiasts have touted coldwater swimming and ice bathing as natural panaceas, capable of dispelling virtually every ill from depression and insomnia to arthritis and subdued libidos.
The evidence behind these claims, however, is often as thin as a crust of lake ice, according to scientists in Norway who have reviewed 104 studies on the subject.
While the researchers found ‘‘positive signs’’ of benign shifts in the body’s biochemistry, they said many of the experiments were too small to be conclusive, and it was often hard to tell if the subjects were healthy because they swam or swam because they were healthy.
There were also a few hints of negative effects.
There has been a strong revival of interest in outdoor swimming since the start of the pandemic. It appears to stimulate mitochondria-rich brown fat, which burns energy to keep the surrounding tissue warm, as well as helping to rein in certain kinds of inflammation.
Three researchers at the Arctic University of Norway and the University Hospital of North Norway read every scientific paper they could find on the ostensible health benefits of bathing in water at 20C or below.
Wild swimmers exhibited elements of a more active immune system, such as elevated levels of white blood cells and several kinds of T cell.
One Czech study involving 10 cold-water swimmers and 16 novices found that the former had much lower risk factors for cardiovascular disease, and reduced chemical markers of stress. However, a separate Czech study of eight seasoned wild swimmers after a set of races found that their blood contained raised levels of troponins, which can reflect damage to heart tissue.
The review was published in the International Journal of Circumpolar Health.