Drinking too much water could kill an athlete

MEDICAL MATTERS

April 22, 2005|By JUDY FOREMAN

Runners at the finish line of this week's Boston Marathon said they had taken very much to heart a series of new warnings about drinking too much water during a race.

"I was conscious of not taking huge amounts of water," said Ian Bloomfield, 52, of England, who pronounced himself "quite pleased" with his time of 2 hours 45 minutes on Monday. "I was very aware of hyponatremia," he added, referring to the potentially fatal result of overhydration.

Brian Paff, 24, of Chicago said he had had hyponatremia in a college race. "I passed out from it," he said. This week, he was careful not to drink too much.

In a dramatic turnabout from years past, sports doctors now have hard evidence that drinking too much water can be as bad as or worse than not drinking enough.

This holds for both endurance athletes and weekend warriors, though most people who exercise for just an hour or so don't need to worry about dehydration or overhydration, and certainly don't need to make heroic efforts to stay hydrated.

In a study published last week in the New England Journal of Medicine, Boston doctors, who have long made Boston Marathon runners their living laboratory, found that hyponatremia (a low concentration of sodium in the blood because of too much water) occurred in a whopping 13 percent of participants.

Of 488 marathoners in the 2002 study, three had such low blood sodium that they were at risk of severe brain swelling, which can lead to brain damage, coma and death.

It was during the 2002 Boston Marathon that 28-year old Cynthia Lucero died of hyponatremia. Worldwide, some researchers believe there may be as many as one death per marathon, though not all are due to hyponatremia.

Sports drinks, once thought to be an athlete's protection against hyponatremia, turn out not to be a guarantee. Though they contain some sodium, it's not enough to make a difference, the study showed.

Many endurance athletes, especially smaller, slower runners who take longer to finish and therefore have more time to drink, actually gain weight during marathons, sometimes as much as 8 to 10 pounds, said Dr. Christopher S.D. Almond, lead author of the study and a cardiology fellow at Children's Hospital in Boston.

Women are at greater risk because they tend to be smaller and slower and also, perhaps, because they may be more diligent at adhering to the old belief that it's wise to drinks lots of water.

Excessive water drinking among athletes has become such a concern among sports doctors that guidelines are rapidly changing. "This has been a major paradigm shift in the last few years," said Dr. Benjamin Levine, co-author of an editorial in last week's medical journal and a cardiologist at the Presbyterian Hospital of Dallas and the University of Texas Southwestern Medical Center.

"It used to be thought that thirst was a poor measure" of impending dehydration and therefore, that athletes should drink as much as they could before thirst set in. "That is clearly not correct," he said.

In 2003, USA Track and Field, which governs track-and-field events, began saying that athletes should use thirst as a guide for fluid replacement. The International Olympic Committee Medical Association began recommending caution in fluid consumption last year, just before the Athens games. The International Marathon Medical Directors Association now advises drinking no more than about 12 to 25 ounces of fluid an hour, especially for slower, back-of-the-pack runners, though that's just a rough guide. The higher number may not be enough for fast runners yet may be too much for slow ones.

Other guidelines now in the works are likely to follow suit, including some from the American College of Sports Medicine and a consensus statement from experts who met recently in South Africa and will publish their recommendations this summer.

This shift in thinking reflects the growing awareness of the dangers of excess fluid consumption.

"Hyponatremia is less common, but more dangerous" than dehydration, said Dr. Peter Moyer, medical director of Boston Fire, Police and Emergency Medical Services. In one study, one-quarter of Boston Marathon participants finished the race dehydrated, but mild dehydration poses little problem.

Dehydration does have clear, adverse effects on performance, which is a major issue for elite athletes, said Michael Sawka, an exercise physiologist and chief of the thermal and mountain medicine division at the U.S. Army Research Institute of Environmental Medicine in Natick, Mass.

"But if you're not doing high-level performance and you're not losing a lot of water, it's not important to drink," he said. "There are no real adverse health consequences except low blood pressure, susceptibility to heat exhaustion and, if you're out there long enough, heat stroke."

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