Professor warns about hyponatremia ahead of Chevron Houston Marathon

HOUSTON, Texas (KTRK) -- Marathoners know better than most to stay hydrated. Your body does need lots of fluid before, during, and after the race, but it's possible to overdo it. That can lead to a condition called hyponatremia.

Hyponatremia can cause weakness, headaches, confusion, nausea, and vomiting. In severe cases, it can cause seizures, coma, and death.

What is the cause? Experts say too much water and not enough sodium.

Sodium is an essential electrolyte that helps regulate how much water is in and around our cells. When our system has too much water and not enough sodium, our cells can swell to dangerous levels.

The Chevron Houston Marathon was one of the first to report cases of hyponatremia in 1999. American College of Sports Medicine fellow Dr. Tamara Hew-Butler was working at a marathon medical tent at the time.

"It was hot that year," she said. "That was the first year that four runners were sent to the emergency room. They were in a coma for a week."

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Today, federal officials estimate that three to six million Americans suffer from hyponatremia annually at the cost of $1.6-3.6 billion. In 2002, a runner in the Boston marathon died from the condition.

That's when Dr. Hew-Butler, also an associate professor of exercise physiology at Wayne State University, left her profession as a podiatrist and focused her research on hyponatremia - much of that research done right here in Houston.

"We did a series of research that showed that some of these runners that were moving a little slower were drinking 100 cups of fluid during the race," she said.

The most dangerous result of too much water and sodium is brain swelling.

"If it swells too rapidly," Dr. Hew-Butler added, "it pushes the brain stem out."

This weekend at the Chevron Houston Marathon, medical tents will have tools to test for hyponatremia.

Those who test positive can simply "pee it out," she said.

Dr. Hew-Butler adds that the best advice to avoid hyponatremia is to only drink when you're thirsty.

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