Are They Really Good for You?

People around the world regularly swim in frigid water, plunge into ice baths, or hop into cold showers. Those who practice cold plunges or other cold therapy say it makes them feel enlivened, improves their mood, and soothes sore muscles. Many believe it boosts their immune system and protects them from cardiovascular and metabolic diseases, including obesity and insulin resistance.

So far, though, the scientific evidence supporting these benefits is pretty scant, and experts caution that shocking the body with cold water could do some people more harm than good.

So before you take the plunge—literally—you should weigh the potential risks and benefits.

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Some Evidence of Benefits Exists

A group of researchers in Norway, who know a thing or two about cold water, conducted a thorough review of published studies touching on the health benefits of voluntary cold-water plunges.

One of the authors, James B. Mercer, Ph.D., professor emeritus at The Arctic University of Norway, notes that only a small number of proper studies are available, and they vary in factors such as the number of subjects, water temperature, and type of immersion. And even when there are clear changes in the body, such as a blood pressure response, it can be difficult to say whether that equates to a health benefit. Plus, many apparent benefits may be due not to cold water, but due to factors like an active lifestyle, social interactions, time spent in nature, a healthy diet, or a positive mindset.

Still, the review found that cold water immersion seems to kick off a number of physiological activities: it burns brown fat—your body’s natural fuel for warmth, affects insulin resistance and sensitivity, lowers cholesterol, and helps regulate stress. Cold water could also be an effective treatment for chronic autoimmune inflammation. Scientific evidence for the benefits of cold water for athletes seems the most solid, with ice baths known to reduce muscle damage and improve recovery time after a hard workout.

“Generally speaking, we felt that evidence of benefits is beginning to appear,” Mercer tells Popular Mechanics. “These activities have become amazingly popular all over the world, and hundreds of thousands of people can’t be wrong. You very rarely meet people who participate who say it is bad for you. And while that is not very scientific, it indicates there probably is something there.”

Cold Water Exposure Both Stresses and Exhilarates

One theory holds that cold water may be good for us because our bodies need a certain amount of physiological stress for adequate brain functioning. Lack of this type of stress can lead to mental health problems, such as depression.

But while there is a lot of anecdotal evidence that cold therapy helps depression, Mercer notes it’s hard to design a scientific study to provide hard evidence. Part of the benefit could be simply due to overcoming the challenge of actually getting into the water, he adds.

Studies about the mental health benefits of swimming in cold water also tend to look at people who swim with others, so it could be the socializing that really matters, according to Dr. Richard A. Friedman, professor of clinical psychiatry at Weill Cornell Medical College. However, cold water exposure appears to increase many substances involved in regulating mood, he tells Popular Mechanics in an email. Healthy subjects immersed in cold water show a spike in the stress hormones cortisol and norepinephrine, and exposure to cold water causes release of endorphins and dopamine, neurotransmitters that convey a sense of pleasure.

Not to mention that swimming is a form of aerobic exercise, which is definitely good for you, and one that is easy on the joints. Dr. Friedman says he has probably prescribed more exercise than antidepressants over the years.

Perhaps not surprisingly, just sitting in cold water may not be as beneficial as exercising in it, although trendy cold plunge tubs often have a social aspect. And a cool shower can have benefits, even though it doesn’t involve exercise or socializing (at least not usually).

Cold water is typically defined as below 60 degrees Fahrenheit; Mercer and his colleagues examined studies involving water from 32 to 68 degrees Fahrenheit. But Dr. Friedman says that exposure to chilly water, between 60 and 70 degrees Fahrenheit, has been shown to boost the same exhilaration-inducing neurotransmitters.

Know The Risks Before You Dive In

Before you dare to feel the “Brrr!” you must remember the potential risks. These include frostbite, hypothermia, heart arrhythmias, and even heart attacks. The American Heart Association cautions that cold water triggers the cold shock response—a sudden, rapid increase in breathing, heart rate, and blood pressure. In addition, blood rushes to the body’s core, reducing circulation in the arms and legs and causing loss of strength and coordination. Hypothermia also makes it harder to think clearly. Water takes heat away from the body 25 times faster than air, triggering hypothermia faster than just by being out in the cold.

Signs of hypothermia

This shock response can be lessened by gradually building up your tolerance and staying submerged for no more than 10 or 15 minutes. And keep your face out of the water; receptors on the face trigger the diving response and can slow your heart rate to as little as 25 or 30 beats a minute. If you opt for the cold shower route, Dr. Friedman suggests gradually turning down the hot water and getting your body used to cooler water over a week or so.

“On balance, the benefits probably outweigh the risks,” Mercer says. “But there are risks, and we have to be aware of those.” He suggests a medical checkup to make sure you are healthy and joining a club or at least finding a buddy to take the plunge with you.

Science Writer

Austin-based science writer and author Melissa Gaskill focuses on ocean issues, endangered wildlife, the environment, and space. She has written for dozens of publications including Mental Floss, Scuba Diving Magazine, Men’s Journal, Alert Diver, Stardate, and Scientific American.