New York Times May 12, 2005
Study Leaves Athletes With Bottles Half-
By VICKY LOWRY
KAREN McGLADE, a 37-year-old schoolteacher from Kent, N.Y., says she has
always tried to drink enough water to stay ahead of feeling thirsty when she exercises.
But after a study published in The New England Journal of Medicine last month
found that drinking too much water can be dangerous, even deadly, Ms. McGlade
now wonders if she's on the right course. "I went for an hourlong run the other day,
and as soon as I got back to my car, I started guzzling water," she said. "Then I started
to think, should I be drinking so much?"
Active people who participate in endurance sports have every right to be confused.
The practical wisdom to drink as much water as possible was scratched after the
widely publicized study of marathon runners showed a high incidence of
hyponatremia, or water intoxication, a condition in which excess water dilutes salt in
the bloodstream, causing the brain to swell and push against the skull.
Athletes are warned that too many liquids can be deadly.
It's a serious problem that can happen during long bouts of exercise, especially in the
heat, when people lose salt through their sweat.
Water has always been the elixir of the healthy, heralded as an absolute essential by
sports doctors and diet gurus alike. Water fountains are around every corner at the
gym, it's sold at yoga studios to be sipped between poses, and it's a staple of sip-top
bottles on bike rides, hikes and even walks. But now it seems too much is not a good
thing. What's a jock to do?
"Just because too much water is dangerous doesn't mean you should stop drinking
fluids," warned Dr. Douglas Casa, the director of athletic training education at the
University of Connecticut in Storrs. "Too much water and your brain becomes
waterlogged. Too little water and your organs shut down."
So how much water should people drink when they exercise? "Enough to replace
sweat," said Dr. William O. Roberts, president of the American College of Sports
Medicine, "and not more than that."
Sports medicine experts recommend drinking enough fluids to maintain your body
weight. One way to find out how much fluid you need to replenish is to weigh
yourself naked before exercise; work out for an hour without drinking; then undress,
towel off and get on the scale again. For each pound lost, you would want to consume
16 ounces per hour, Dr. Roberts explained.
In simpler terms, drink just enough to avoid dehydration, and don't force fluids. For
example, you don't need to stop and drink at each refreshment station during a
marathon. That's why average athletes are more at risk for hyponatremia than elite
runners, "who don't have time to drink a lot of water, otherwise they'd lose the race,"
said Dr. Benjamin Levine, a cardiologist at the University of Texas Southwestern
Medical Center and director of the Institute for Exercise and Environmental Medicine
"If you are drinking large volumes of water over the course of the marathon, and your
wedding ring feels tight, or you feel puffy, it's probably time to stop," explained Dr.
W. Larry Kenney, a professor of physiology and kinesiology at Penn State University
and a former president of the American College of Sports Medicine. If your muscles
start to cramp, it could be a sign of overhydration. Feeling dizzy? Seek medical
attention, Dr. Kenney advised.
Women, especially petite women, are more vulnerable to hyponatremia, but experts
aren't sure why. Weight is a factor: "If both men and women drink a gallon of water
in the course of a race, the smaller woman dilutes her blood more than the male," Dr.
Women may also be too conscientious about dehydration. "If you ask a male runner
how much he drank in a race, he'll say two swallows, while a woman will say two
glasses," Dr. Roberts said.
If you are planning to exercise for several hours, consider consuming more salt along
the way. This advice applies especially to heavy sweaters and high-salt sweaters; you
are one if your face and clothing are crusted white after a workout.
Dr. Mark Tarnopolsky, a specialist in neuromuscular disorders and an adventure racer
in Hamilton, Ontario, recommends snacking on pretzels or Pringles (his personal
favorite), adding a pinch of salt to a water bottle or consuming sports drinks with
extra sodium. (Gatorade's new Endurance Formula, for example, has 200 milligrams
of sodium, compared with its regular Thirst Quencher with 110 milligrams.)
Finally, don't panic, Dr. Levine advised. "For the vast majority of exercisers, if they
just drink when they are thirsty and accept a mild degree of dehydration - which isn't
that terrible and which they may or may not get - they will be just fine."