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The power of a very cold plunge

The mental and physical benefits of swimming in frigid waters are finally becoming better understood.

A Russian Orthodox believer immersed in frigid water during a traditional Epiphany celebration in Moscow in January.
A Russian Orthodox believer immersed in frigid water during a traditional Epiphany celebration in Moscow in January.Pavel Golovkin/Associated Press

Last weekend, I went to the beach. To swim. In the English Channel.

Sea temperatures in the Channel are never exactly warm, but in the middle of October, the water was a bracing 54 degrees Fahrenheit. I wore a swimsuit, swim cap, and goggles. After 25 minutes, my fingers were white and useless; after 40 minutes, electric zings raced up my arms every time I stretched into my stroke. When I got out after 50 minutes, I couldn’t feel the stones on the beach bruising my feet because I couldn’t feel my feet.

But I felt great. Genuinely. Swimming or bathing in cold water has been a “cure” at least as far back as the “father of medicine,” Hippocrates, who regularly prescribed cold (and hot) baths for various ailments. In the early 18th century, medical treatises like physician J.S. Hahn’s excessively titled book, “On the Healing Virtues of Cold Water, Inwardly and Outwardly Applied, as Proved by Experience,” made the rounds of European medical circles, inspiring other physicians and healers; soon, “hydrotherapy” or “hydropathy” became part of the expanding medical marketplace. Thomas Jefferson reportedly swore by a cold foot bath every morning to “maintain his good health.” “Sea bathing” — especially in winter — was meant to be particularly healthful. The first sea bathing hospital in Britain was founded by a Quaker physician in 1791.

Cold water therapy fell out of fashion with the rise of drugs and surgery, but maybe it shouldn’t have. More and more evidence is suggesting that Hippocrates and Hahn were on to something. Scientists are exploring whether even a once-a-week plunge in frigid waters can alleviate anxiety, depression, chronic pain, and the symptoms of menopause.


Just this week, scientists from the UK Dementia Research Institute at the University of Cambridge told the BBC that cold water swimming might protect the brain from developing dementia.


Professor Giovanna Mallucci’s research group has found that the utter physical panic of the body’s response to cold water generates “cold shock proteins,” including one, RBM3, that is also implicated in the formation of new synaptic connections in the brain. After demonstrating how the protein functioned in hypothermic mice, the researchers wanted to find the protein in humans. Forcing people into hypothermia, however, is frowned upon by human subject research approval boards. Luckily, a group of winter swimmers at Parliament Hill Lido, an open-air, unheated swimming pool in London where water temperatures dip as low as 40 degrees Fahrenheit, stepped up to the task. Over the course of three consecutive winters, Mallucci’s lab found that many of the swimmers exhibited remarkably high levels of the protein, higher than the control group, members of a tai chi club who practiced beside the pool through the winter. Notably, all of the swimmers became clinically hypothermic during their swims.

This latest study is still unpublished, but the neuroprotective role of RBM3 has been seen in previous research. Mallucci’s group hopes that pinning down why it works will be useful in the potential development of therapies for people suffering from Alzheimer’s and dementia — no cold water required.

Linda Rodriguez McRobbie is a freelance writer in London.