Amateur and professional runners often drink plenty of water to avoid dehydration. But as racers prepare for The ING New York City Marathon, some experts are warning that overhydration is equally dangerous.

In a study published in the British Journal of Sports Medicine last September, researchers found that almost one in ten runners drink as much water as possible when running. This can lead to Exercise-Associated Hyponatraemia – a condition associated with overhydration that depletes sodium levels in the body.

Common symptoms include gastrointestinal problems, cramping and nausea. EAH also can lead to seizures, respiratory arrest and even death, if left untreated.

Only 28.5 percent of the nearly 200 runners surveyed follow scientific hydration guidelines, researchers found. Fluid intake during exercise is highly individual and depends on a person’s height, weight and level of exertion, said Laura Dugas, one of the study’s authors.

The misconception that runners need to drink as much water as possible is the result of corporate advertising and marketing “disguised as strict scientific recommendations,” the study suggests.

“Sports drink companies make people think that even being slightly dehydrated is
dangerous,” Dugas said.