How Much Is Too Much Water?

Drinking excess water while working out may be dangerous

Before you put your workouts on turbo drive, you may want to consider this advice.

An expert panel has issued new guidelines regarding water intake during exercise. According to the panel, which included experts in sports medicine, nutrition and athletic training, it’s better to be guided by thirst than to drink too much in an effort to stay ahead of water loss.

"Aggressive drinking to prevent dehydration is unnecessary and carries with it greater risk," according to the guidelines.

According to panel member and author of multiple studies on hyponatremia in athletes James Winger, MD, many athletes often are mistakenly advised to "push fluids" or drink more than their thirst dictates — often by drinking until their urine is clear or drinking to a prescribed schedule.

But excessive fluid intake does not prevent fatigue, muscle cramps or heat stroke, according to Dr. Winger.

"Muscle cramps and heatstroke are not related to dehydration," said Dr. Winger, in a press release. "You get heat stroke because you're producing too much heat."

Hyponatremia (low blood sodium) occurs when there is so much fluid in the body that the kidneys cannot get rid of the excess. Hyponatremia can be life-threatening.

The panel recommends that athletes drink only when thirsty rather than to a prescribed amount.

The dangers of over-drinking can be serious. At least 14 athletes — including a woman who died two days after completing the Marine Corps Marathon in 2002 — are believed to have died from drinking too much during exercise, reports The Washington Post.

According to Dr. Winger, modest to moderate levels of dehydration pose little risk to healthy athletes — an athlete can safely lose up to 3 percent of his or her body weight during a competition due to dehydration without a loss in performance.

According to the panel, sports drinks can also make hyponatremia worse if an athlete drinks a lot of them, as they contain less sodium than body fluids. Sodium supplementation in modest amounts may be helpful for athletes, but excess sodium may also have dangers, according to the panel.

The new guidelines were published in the July issue of the Clinical Journal of Sport Medicine.