From the rise in polar swims to the explosion of trendy bathhouses offering group cold plunges and CEOs like Jack Dorsey touting ice baths, it seems like taking an icy dunk is the hottest wellness trend.
But is it really good for you?
That’s the question a group of University of South Australia researchers set out to answer through their unique meta-analysis of 11 global studies. But the results, published in the PLOS One journal on Jan. 29, were murky.
The researchers analyzed studies of cold-water immersion (CWI), through plunges or showers in a range of 44 to 59 degrees Fahrenheit, for durations of at least 30 seconds and up to two hours. And the findings were—sorry, Wim Hof!—very mixed: There are some possible benefits, but not a ton, and they are mostly without staying power.
“CWI has gained widespread popularity among the general public, despite most evidence focusing solely on its effects among athletic populations,” the researchers note in the study about their motivation. “This knowledge gap is particularly concerning given the increase in consumer adoption of CWI, with largely unsupported claims in mainstream media about its benefits for physical health and mental wellbeing.”
Chilly water and stress, sleep
One of the top benefits, according to the analysis, was a significant reduction in stress—but only at 12 hours post-immersion. No evidence of such reductions was seen immediately—nor at one hour, 24 hours, or 48 hours after the plunge.
Also observed, on the positive side, were improvements in sleep quality—although more research is needed here, as the study on this topic was limited to men.
Perhaps most promising, though, was a 29% reduction in sick-related work absences among those who took cold showers. Still, the meta-analysis showed no significant effects on immune function either immediately or one hour post-immersion.
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Cold plunging and inflammation
One of the most surprising findings, considering how celebs from LeBron James to Lady Gaga swear by ice baths for post-performance recovery, was the effect of cold plunges on inflammation: Instead of it reducing the inflammation, according to the researchers, it led to “significant increases in inflammation,” both immediately and one hour post-immersion. This, according to the study authors, indicates “an acute inflammatory response.”
“At first glance this seems contradictory, as we know that ice baths are regularly used by elite athletes to reduce inflammation and muscle soreness after exercise,” study coauthor Ben Singh said in a news release. “The immediate spike in inflammation is the body’s reaction to the cold as a stressor. It helps the body adapt and recover and is similar to how exercise causes muscle damage before making muscles stronger, which is why athletes use it despite the short-term increase.”
But, he added, “knowing this, people with preexisting health conditions should take extra care if participating in cold-water immersion experiences, as the initial inflammation could have detrimental health impacts.”
The bottom line is that much more research is needed into the practice of cold plunging. And, stresses lead study author Tara Cain, “Whether you are an elite athlete or everyday wellness seeker, it’s important to understand the effects of what you put your body through.”
More on wellness trends:
- This 48-year-old CEO wakes up at 4:15 a.m. to work out and meditate. Here’s his daily routine
- Are cold plunges and saunas safe for kids?
- The key to a long life is avoiding the ‘poisonous 5 P’s,’ says one of the world’s top anti-aging experts
