The health benefits of ‘ice swimming’ are still unclear

With summer losing its grip on the Northern Hemisphere, long days at the beach eating ice cream or splashing in the ocean are long gone for most. But for some swimmers, the fun is just beginning.

“It is best to go to Brighton Beach in the fall. Every week the water is a little colder than the last. Before you know it it will be 48 degrees!” Bonnie Schwartz Nolan, a management, surgery and financial advisor, swim coach and successful English Channel swimmer from New York, tells Popular science. She’s been bobbing in the cold waters of Brooklyn for over two decades.

To train for most marathon swims (a swim of more than 10km or 10km), swimmers must get used to spending time in the cold, as swimmers often cannot wear a wetsuit or technical suit to keep warm and instead have to rely on their own bodies.

“Your core temperature is 98 degrees, so even something like 80 degrees will feel cold after a while,” explains Nolan. To even qualify to swim in the English Channel, swimmers must undergo a documented six hours under 60, or a continuous dive in water below 60 degrees Fahrenheit (about 15 degrees Celsius).

[Related: Swimming is the ultimate brain exercise. Here’s why.]

Swimming in open water has even evolved into ice swimming or swimming in waters below 41 degrees Fahrenheit (5 degrees Celsius). For me, it’s all about the challenge,” said Elaine K. Howley, a journalist and accomplished swimmer, in an interview with PopScic. “It’s that uncertainty about ‘can I do it,’ the same way as marathon swimming.” Howley is an accomplished marathon and ice swimmer who completed an ice mile in 2012 and is currently training for her second.

Some anecdotal “wellness” claims, including weight loss, better mental health and increased libido, have been made by supporters of regular cold water immersion, but what about concrete evidence?

A scientific review published today in the peer-reviewed International Journal of Circumpolar Health notes that a dip in cold water can reduce white adipose tissue (WAT) in men and reduce the risk of conditions like diabetes, but other benefits of ice swimming are inconclusive.

The authors analyzed 104 scientific studies and found an additional impact on brown adipose tissue (BAT). The difference between the two is that WAT stores energy instead of burning it like BAT does. Repeated exposure to cold water or air increases the production of BAT, which is also found in the blubber of marine mammals such as whales and seals to keep them warm.

BAT helps the body burn calories, retains body heat when exposed to cold temperatures, and also helps the body control blood sugar and insulin levels. It produces heat in the blood when it is cold outside and is mainly around the neck, kidneys, adrenal glands, heart and chest in adults. According to the Cleveland Clinic, it is brown because the fat cells are full of mitochondria, which are high in iron. The iron gives BAT the brown tint.

Exposure to cold water or air also appears to increase adipose tissue’s production of a protein called adiponectin. This is a protein that plays a key role in protecting against insulin resistance, diabetes and other diseases. According to the data reviewed in these studies, repeated cold water immersion in winter increased insulin sensitivity and significantly decreased insulin concentrations. This occurred in both inexperienced and experienced swimmers.

Swimming in cold water also has a major impact on the body, triggering a shock response such as an increased heart rate. Some of the reviewed studies showed evidence that cardiovascular risk factors actually improved in swimmers who have adapted to the cold. However, other studies suggest that the load on the heart is still increasing. All in all, the authors were inconclusive about the overall health benefits of the ‘fastest growing extreme water sport’.

“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 The Arctic University of Norway, in a press release.

According to the authors, many of the available studies examining the health benefits of ice swimming involved a small number of participants, often of one gender, and did not take into account differences in water temperature or whether the water was fresh or salty. It is also unclear whether winter swimmers are naturally healthier than the general population.

[Related: How to avoid (and treat) hypothermia.]

“Many of the studies have shown significant effects of cold water immersion on various physiological and biochemical parameters. But whether or not these are beneficial for health is difficult to estimate. Based on the results of this review, many of the health benefits claimed from regular cold exposure may not be causal. Instead, they can be explained by other factors, including an active lifestyle, trained stress management, social interactions and a positive mindset,” Mercer added.

The authors point out that swimmers who participated in these studies ranged from elite swimmers or established winter swimmers to those with no previous ice swimming experience. Some were strictly ice bathers, but used cold water immersion as a post-exercise treatment.

The review also found that there is a need for better education about the health risks associated with taking a dip in icy water. These include hypothermia if a swimmer is in the water for too long or jumps in without acclimating, as well as heart and lung problems related to the shock of the cold. Simply jumping into cold water is very dangerous and it is best to start ice swimming slowly over a period of time.

If swimming in icy water sounds like fun, Howley and Nolan recommend taking progressively longer dips in colder water to acclimate. Nolan also took cold showers, slept with the windows open and a lighter blanket, and wore a vest instead of a jacket outside to help her body acclimate to the frigid temperatures.