Cold Water Swimming and Your Health?
Down at Aquatic Park, Dr. Thomas Nuckton was stripped to his swimsuit and neck deep in 50-degree bay water. And he wasn't alone. Winter is the time of year that the truly devoted - or truly crazy - swimmers come out, those hardy folk who dive nearly naked into San Francisco Bay, into waters 25 or 30 degrees colder than the average swimming pool. The health benefits of these swims are debatable, the risks less so. And yet every year, dozens, maybe a hundred, people swim all through the winter months, putting in miles and hours in the water. "People will go down there to swim, and it's almost like a spiritual experience," Nuckton said. "It's not quite the same for me. I hate getting in the water," he added with a laugh. "But I have my good days. And I'd much rather be there than in a pool, staring at a black line and just going back and forth." Nuckton is a doctor at UCSF and California Pacific Medical Center, focused primarily on studying survival prognoses for patients in intensive care wards. But he's taken a side interest in swimming and, in particular, the effects of cold-water dips.
Nuckton's most recent study was prompted by a comment he overheard from a tourist standing on the Hyde Street Pier, watching the Aquatic Park swimmers. "He pointed at the swimmers and said, 'They're fatter than us. That's how they endure the cold,' " Nuckton recalled.
There is no doubt, doctors say, that regular cold-water swimmers are healthier overall than most Americans. But whether it's the cold or the simple act of regular exercise that helps them is unclear.
"I'm not convinced that, physiologically speaking, cold-water swimming helps. I think these people are already healthy to begin with and they want to challenge their bodies," said Dr. Malini Singh, medical director of emergency medicine at San Francisco General Hospital. There are theories, but not much evidence, about how cold water can improve health. Some studies have shown that people who swim through the winter have higher immune cell counts than nonswimmers. And some scientists, and swimmers, have speculated that cold-water swimming increases production of what's known as brown fat, thought to be a healthy fat that burns energy and creates heat. Many cold-water swimmers believe they're burning more calories in the bay as their bodies struggle to stay warm than they would in a heated pool, but scientists aren't convinced that's the case. Cold water, in fact, slows the metabolism, which may mean that the body is actually burning fewer calories. Even if there is a larger calorie burn, it's probably negligible, doctors say.
It's not just the benefits of cold-water swimming that are tough to document. The risks are poorly understood and probably overstated too, some doctors said. Two studies of athletes competing in long-distance, open-water swims found that most of them were suffering mild hypothermia by the end of the race, even when the water temperatures were in the 60s or higher. "I know people do it. Anecdotally speaking, they say they feel refreshed, they feel less stress and less fatigue," she added. "But I've been in that water, in a wet suit, and I just felt terribly cold to my bones." Nuckton studied 11 participants in a 2000 Alcatraz swim and found that five were suffering mild hypothermia by the end of the event. And perhaps more concerning, their temperatures continued to drop after they got out of the water. But mild hypothermia on its own is not necessarily a dangerous thing. In Nuckton's study, most swimmers' temperatures dropped about 2 degrees below normal, which probably wouldn't produce any noticeable symptoms or discomfort. In order for hypothermia to cause major damage or become deadly, the body temperature needs to drop to the low 90s.
|Last week, the Bay Area was quivering through a cold snap, and the tourists along Fisherman's Wharf were, for once, dressed for the weather, bundled in jackets and scarves, mittens and caps.|
|Aided by extra fat? More fit, but why? Risks overstated Peril of sudden shock|