People are plunging into frigid water for their social media feeds, but the science on benefits is lukewarm

People are plunging into frigid water for their social media feeds, but the science on benefits is lukewarm

The coolest thing on social media these days might be celebrities and regular people diving into freezing water or taking ice baths.

The proposed benefits include improved mood, more energy, weight loss and reduced inflammation, but the science supporting some of those claims is lukewarm.

Kim Kardashian posted her outing on Instagram. Harry Styles tweeted about his dips. Kristen Bell says her dives are “brutal” but uplifting. And Lizzo claims that ice dipping reduces inflammation and makes her body feel better.

Here’s what medical evidence, experts and fans say about the practice, which dates back centuries.


You can call Dan O’Conor an amateur authority on cold water immersion. Since June 2020, the 55-year-old Chicago man has been diving in Lake Michigan almost daily, including on freezing winter mornings when he has to kick through the ice.

“The endorphin rush … is an incredible way to wake up and just kind of jolt the body and get the engine going,” O’Conor said on a recent morning as the air temperature dipped to a frigid 23 degree wash. Endorphins are “feel good” hormones released in response to pain, stress, exercise and other activities.

With the lake temperature at 34 degrees, the bare-chested O’Conor did a running jump from the snow-covered bank to launch a forward spin into the icy gray water.

His first dip came early in the pandemic, when he went on a bourbon bender and his exasperated wife told him to “go jump in the lake.” The water felt good that June day. The world was in a coronavirus funk, O’Conor says, and that made him want to keep going. As the water got colder with the seasons, the psychological effect was even greater, he said.

“My mental health is much stronger, much better. I found some Zen down here come down and jump into the lake and shock that body,” O’Conor said.

Dr. Will Cronenwett, chief of psychiatry at Northwestern University’s Feinberg medical school, tried cold water immersion once years ago while visiting Scandinavian friends on a Baltic island. After a sauna, he jumped into the ice-cold water for a few minutes and had what he called an intense and invigorating experience.

“It felt like I was being stabbed with hundreds of millions of very small electric needles,” he said. “I felt like I was strong and powerful and could do anything.”

But Cronenwett says studying cold water immersion with a gold-standard randomized controlled trial is challenging because designing a placebo for cold immersion can be difficult.

There are a few theories about how it affects the psyche.

Cronenwett says cold water immersion stimulates the part of the nervous system that controls the state of rest or relaxation. It can enhance feelings of well-being.

It also stimulates the part of the nervous system that regulates the fight-or-flight stress response. Doing so regularly may dampen that response, which in turn may help people be better able to deal with other stressors in their lives, although this has not been proven, he said.

“You have to overcome your own trepidation. You have to muster up the courage to do it,” he said. “And when you finally do, you feel like you’ve achieved something significant. You have achieved a goal.”

Czech researchers found that cold water plunges can increase blood concentrations of dopamine – another so-called happy hormone made in the brain – by 250%. High amounts are linked to paranoia and aggression, noted physiologist James Mercer, a professor emeritus at the Arctic University of Norway who co-authored a recent scientific review of cold water immersion studies.


Cold water immersion increases blood pressure and increases stress on the heart. Studies have shown it is safe for healthy people and the effects are only temporary.

But it can be dangerous for people with heart problems, sometimes leading to life-threatening irregular heartbeats, Cronenwett said. People with heart conditions or a family history of early heart disease should consult a doctor before diving, he said.


Repeated cold water immersions during winter months have been shown to improve how the body responds to insulin, a hormone that controls blood sugar levels, Mercer noted. This may help reduce diabetes risks or keep the disease better under control in people who are already affected, although more studies are needed to prove this.

Cold water immersion also activates brown fat – tissue that helps keep the body warm and helps control blood sugar and insulin levels. It also helps the body burn calories, which has led to research into whether cold water immersion is an effective way to lose weight. The evidence so far is inconclusive.


Anecdotal research suggests that people who regularly swim in cold water get fewer colds, and there’s evidence that it can increase levels of certain white blood cells and other infection-fighting substances. Whether an occasional dunk in ice water can produce the same effect is unclear.

Among the biggest unanswered questions: How cold does water need to be to achieve any health benefits? And will a quick dunk have the same effect as a long swim?

“There is no answer to ‘the colder the better,'” Mercer said. “It also depends on the type of reaction you’re looking at. For example, some occur very quickly, such as changes in blood pressure. … Others, such as the formation of brown fat, take much longer.”

O’Conor dunks year-round, but he says winter dunks are best for “mental clarity,” even if they sometimes only last 30 seconds.

On those freezing mornings, he “blocks out everything else and knows that I have to get in the water, and then more importantly, get out of the water.”

— By LINDSEY TANNER, AP Medical Writer

The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Science and Educational Media Group. The AP is solely responsible for all content.

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