Why Too Much Water Can Actually Be Deadly

Water has been touted as a wonder drink thanks to having zero calories and being the number one beverage for dehydration. But for some long endurance athletes it could potentially be fatal.

Doctors say some athletes can develop a condition called water intoxication, which happens within the body when a person’s consumption of water dilutes the salt level in the blood.

“When sodium [salt] concentrations are low in the blood, it actually allows water to leak out of the blood into the other tissues,” a condition known as hyponatremia,” said Dr. Aaron Baggish, associate director of the Cardiovascular Performance Program at the Massachusetts General Hospital Heart Center.

The organ most affected by hyponatremia is the brain. And as water leaks out of the blood and into the brain cells, it causes the brain to swell. Symptoms of this condition include mild confusion, headache and nausea. But if not treated, these health issues can escalate to seizures.

The worst cases of this condition is called brain herniation, which happens when the organ continues to swell uncontrollably. This could be potentially fatal.

“The brain is soft tissue that’s contained in a fixed skull. When the brain swells, there’s only one real way it can go as an exit path, and that’s down to the bottom of the skull where there’s a hole that connects the brain to the spinal cord,” Baggish said.

Long Running Endurance Athletes Are Most At Risk

Sports medicine doctors see far more cases of water intoxication and hyponatremia than family practitioners. Among those most at risk for water intoxication are marathoners who stay on the course for long periods of time. This often means average runners, as opposed to elite athletes.

“Slower runners have more time to drink water,” said Dr. William Roberts, a former president of the American College of Sports Medicine. “If you’re out there for six hours, walking through water stops and drinking more than you need, you could end up in this situation.”

How To Avoid Water Intoxication

Dr. Robert Glatter, an emergency physician with Lenox Hill Hospital in New York City, recommends taking salt or sodium during a race to minimize the chances of hyponatremia.

In addition, Baggish recommends drinking water only when you’re thirsty, not before. ”You should be drinking if you’re feeling mildly thirsty, he said. “But if you’re not thirsty there’s no point to pound water because it’s not going to make you perform better.”

Roberts adds that it’s best to figure out your water-loss rate before your event. “That gives you an idea how much fluid you lost,” Roberts said. “Plan on drinking about that much during your event.”