Marathon Runners Drink Too Much
Study: Dangerous Salt Loss Linked to Drinking Too Many Fluids
April 13, 2005 -- One in three marathon runners drinks more fluids than she
or he needs, a study of Boston Marathon runners shows.
In the 2002 Boston Marathon, one female runner died because her body lost
too much salt, a condition known as hyponatremia. Many of her race mates risked
the same fate, find Christopher S.D. Almond, MD, MPH, and colleagues.
Almond's team got blood samples and other data from 488 women and men who
ran the 2002 Boston Marathon. They found that 13% of the runners had low sodium
levels. And three of the 488 runners analyzed had critically low sodium levels
-- putting them at very high risk of headache, confusion, seizures, and
Since 15,000 people ran the race, this means that nearly 1,900 of the
runners had too-low sodium levels at the end of the race. And some 90 runners,
Almond and colleagues estimate, had critically low sodium levels. The main
drinking too many fluids during the race, diluting the body's salt.
"These observations suggest that hyponatremia -- and particularly severe
hyponatremia -- may be a greater problem than previously recognized,"
Almond and colleagues report in the April 14 issue of The New England
Journal of Medicine.
Sport Drinks Not a Solution for Salt Loss
In terms of salt loss, it didn't seem to matter whether runners drank pure
water or sports drinks. That's because
a lot more water than salt.
"Our findings suggest that the contribution of the type of fluid is
small as compared with the volume of fluid ingested," Almond and colleagues
An editorial accompanying the Almond study underscores this point.
"It is important to recognize that currently available 'sports drinks'
are not protective: Most ... provide far more water than salt," write
Benjamin D. Levine, MD, director of the Institute for Exercise and
Environmental Medicine at the University of Texas Southwestern Medical Center
in Dallas; and Paul D. Thompson, MD, director of preventive cardiology at
Connecticut's Hartford Hospital.
Levine and Thompson note that the problem isn't limited to marathon runners.
All kinds of athletes tend to drink too many fluids. According to the American
College of Sports Medicine, water and sports drinks aren't dangerous to
athletes when used as recommended -- in amounts that approximate sweat
A problem for athletes has been recent advice to Dehydration can indeed be a terrible problem, resulting
in muscle damage and death.
while exercising and not to wait
until one is thirsty.
So how can you strike a balance between dangerous salt loss from
overhydration and dehydration? Almond and colleagues note that individuals vary
widely in their need for water and in the rate at which they lose water. The
researchers suggest that runners weigh themselves before and after practice
races. If you weigh more after a race than before the race, you drank too much.
Adjust your fluid intake accordingly, preferably with sodium-containing fluids
that replace salt lost from sweating.