In the
sparkling sunshine yesterday, runners at the finish
line of the Boston Marathon said they had taken very
much to heart the 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. ''I was very aware of
hyponatremia," 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. Yesterday, he was careful not to
drink too much.
In a dramatic turnabout, sports doctors now say that
drinking too much water can be as bad 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 really
need to worry about either dehydration or
overhydration.
In a study published last week in the New England
Journal of Medicine, Boston doctors, who have long
made Marathon runners their living laboratory, found
that hyponatremia (a low concentration of sodium in
the blood because of too much water) occurred in 13
percent of participants. Of the 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 Lucerodied 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.
Even 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. Women are at greater risk because they
tend to be smaller and slower and also, perhaps,
because they may more diligently adhere to the old
belief that it's wise to drink lots of water.
Excessive water drinking among athletes has become
such a concern among sports doctors that guidelines
are rapidly changing. At major endurance races
around the country, including yesterday's marathon,
doctors now do an on-the-spot test for blood sodium
levels on collapsed runners to differentiate between
hyponatremia and dehydration. Giving fluids
to someone with hyponatremia could be
fatal.
The Boston Marathon has had these tests at the
finish line for several years and this year, for the
first time, had them along the course as well. In
addition, Marathon officials provided scales along
the route and at the finish line, and encouraged
runners to write their pre-race weight on their bibs
to check for weight gain.
''This has been a major paradigm shift in the last
few years," said Dr. Benjamin Levine, coauthor of an
editorial in last week's medical journal and a
cardiologist at the Presbyterian Hospital of Dallas.
''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 prior to 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.
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 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.
Dehydration does have clear, adverse effects on
performance, which is a major issue for elite
athletes, said Michael Sawka, chief of the
thermal and mountain medicine division at the US
Army Research Institute of Environmental Medicine in
Natick.
''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" to dehydration, except low
blood pressure, ''susceptibility to heat exhaustion
and, if you're out there long enough, heat
stroke."
Like hyponatremia, heat exhaustion does make people
feel ill, get nauseous, have muscle cramps and feel
dizzy upon standing up quickly; heat stroke includes
all that plus mental-status changes, such as
confusion about
one's identity and location.
But dehydration ''would have to be extreme and
prolonged, like being lost in the Sahara for days,
to become fatal," said Dr. William G. Goodman,
a kidney specialist at the David Geffen School of
Medicineat UCLA.
So how can you tell how much fluid you need during
exercise? The best approach is to weigh yourself
before and after exercise, said Dr. Arthur Siegel,
chief of internal medicine at McLean Hospital in
Belmont. If you lose, say, 3 percent of your body
weight after a workout, ''that represents mild
dehydration," he said. It is enough, though, to be
a ''green light" to rehydrate slowly, over eight to
12 hours.
If you gain 3 percent of body weight, that's serious
-- a red flag
or hyponatremia.
So, whether you're a marathoner or a casual athlete,
make it a point to weigh yourself before and after
workouts. If you do gain weight, don't drink fluids
(salty broth is OK if you have a headache or salt
craving) until after you have urinated
spontaneously. The point is to let your body get rid
of excess water.
Judy Foreman’s column appears every other week.
Past columns are available on
www.myhealthsense.com.
