Too Much Of A Good Thing

For some endurance athletes, drinking too much water during extended training sessions can be dangerous, says a Tufts expert.

Boston [07.11.02] -- For many endurance athletes - who push themselves to the limit for hours at a time - fluids are essential during their training. But drinking too much water, says an expert at Tufts' Medical School, can cause a rare but dangerous condition that can lead to brain damage and even death.

Hyponatremia - sometimes called water intoxication - is caused when levels of sodium in the blood drop to dangerously low levels.

"Typically, conscientious athletes get in trouble because they adhere too diligently to one recommendation (drink lots of fluids), but ignore another (keep electrolytes up.)," reported the Los Angeles Times. "Electrolytes are charged particles such as sodium, potassium, calcium and bicarbonate that must be kept in near-perfect balance."

As athletes sweat, they lose water and electrolytes. Replacing both - while keeping them in balance with one another - is extremely important, says Tufts' Dr. Ronenn Roubenoff - a professor of medicine and nutrition and the director of human studies at the University's USDA Human Nutrition Research Center on Aging.

"[According to Roubenoff], normally, sodium is plentiful in the blood and relatively low inside cells," reported the Times. "But when the concentration in the blood gets too low compared to the amount inside cells - either because a person drank too much water, took in too little sodium, or both - water rushes into the cells."

When that happens, the Tufts expert says athletes are at risk.

"The result is dangerous swelling - particularly in the brain - that can lead to brain damage, coma and death," reported the newspaper. "Curiously, hyponatremia can occur whether a person is dehydrated, normally hydrated or overhydrated because any of those conditions happen while blood levels of sodium are low, adds Roubenoff."

Sodium is just one of the electrolytes that need watched. "An imbalance of any one of the electrolytes can be harmful," Rubenoff told the Times.

Because its symptoms mimic others, the rare condition can be difficult to diagnose.

"The symptoms of hyponatremia can be easily confused with those of heatstroke and heat exhaustion," reported the Times. In both cases, people feel nauseated, dizzy --- even suffer from confusion.

But as long as athletes keep their fluids and electrolyte levels in balance, they should be able to stay healthy during long workouts, Rubenoff said.