Perhaps the coolest thing about social media these days is celebrities and regular people throwing themselves in cold water or taking ice baths.
The touted benefits include improved mood, increased energy, weight loss and reduced inflammation, but the science supporting some of these claims is lukewarm.
Kim Kardashian posted her foray on Instagram. Harry Styles tweeted about his dips. Kristen Bell says her jumps are “brutal” but mentally uplifting. And Lizzo claims ice diving reduces inflammation and makes her body feel better.
Here’s what medical evidence, experts, and fans are saying about the practice, which dates back centuries.
THE MIND
You could call Dan O’Conor an amateur cold-water immersion expert. Since June 2020, the 55-year-old Chicago native has thrown himself into Lake Michigan almost every day, including on cold winter mornings when he has to shovel through the ice.
“The endorphin rush… is an incredible way to wake up and just shock the body and get the engine running,” O’Conor said on a recent morning when the air temperature was a freezing 23 degrees (minus 5 degrees Celsius). Endorphins are “feel good” hormones that are released in response to pain, stress, exercise, and other activities.
With a sea temperature of 34 degrees (1 degree Celsius), the shirtless O’Conor took a running leap off the snow-covered shore to launch a forward somersault into the icy gray water.
His first jump came early in the pandemic when he went on a bourbon bender and his angry wife told him to “jump in the lake.” The water felt good that June day. The world was on a coronavirus funk, O’Conor says, and that drove him to keep going. As the water got colder with the seasons, the psychological effect was greater, he said.
“My sanity is much stronger, much brighter. I found some zen down here that came down and jumped into the lake and shocked that body,” O’Conor said.
dr Will Cronenwett, director of psychiatry at Northwestern University Medical School in Feinberg, tried cold water immersion years ago while visiting Scandinavian friends on a Baltic island. After a sauna session, 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 really small electric needles,” he said. “I felt like I was strong and powerful and could do anything.”
However, Cronenwett says studying cold-water immersion with a gold-standard randomized controlled trial is challenging because developing a placebo for cold-diving could be difficult.
There are some theories as to how it affects the psyche.
According to Cronenwett, immersion in cold water stimulates the part of the nervous system that controls the state of rest or relaxation. This can increase well-being.
It also stimulates the part of the nervous system that regulates the fight-or-flight stress response. Doing it regularly can dampen that response, which in turn might help people feel more empowered to deal with other pressures in their lives, although this hasn’t been proven, he said.
“You have to overcome your own fear. You have to have the courage to do it,” he said. “And when you finally do it, you feel like you’ve accomplished something significant. You have achieved a goal.”
Czech researchers found that cold water can increase blood concentrations of dopamine – another so-called happiness hormone produced in the brain – by 250%. High levels have been linked to paranoia and aggression, noted physiologist James Mercer, a professor emeritus at the Arctic University of Norway and co-author of a recent scientific review of cold water immersion studies.
THE HEART
Cold water immersion raises blood pressure and increases the workload on the heart. Studies have shown that this 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 disease or a family history of early heart disease should consult a doctor before diving, he said.
METABOLISM
Repeated cold water immersion during the winter months has been shown to improve the body’s response to insulin, a hormone that controls blood sugar levels, Mercer noted. This could help reduce the risk of diabetes or better control the disease in those who already have it, although more studies are needed to prove this.
Cold water immersion also activates brown fat — tissue that helps keep the body warm and helps it 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.
IMMUNE SYSTEM
Anecdotal research suggests that people who routinely swim in cold water get fewer colds, and there’s evidence that doing so may increase levels of certain white blood cells and other infection-fighting substances. Whether an occasional dip in ice water can achieve the same effect is unclear.
One of the biggest unanswered questions: How cold does water have to be to get health benefits? And will a quick dip have the same effect as a long swim?
“There’s no answer to ‘the colder the better,'” Mercer said. “Also, it depends on the type of reaction you’re looking at. For example, some occur very quickly, such as changes in blood pressure. … Others, like brown fat formation, take much longer.”
O’Conor dives year-round, but he says winter dunks are best for “mental clarity,” even if they sometimes only last 30 seconds.
On those frigid mornings, “he locks everything else out and knows I need to get in the water and, more importantly, out of the water.”
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Follow ` Medical Writer Lindsey Tanner at @LindseyTanner.
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