Nearly half of recreational runners may be drinking too much fluid during races, according to a recent survey of runners, published in the British Journal of Sports Medicine.

Expert guidelines recommend runners drink only when thirsty, but the survey found that 36.5 percent of runners drink according to a preset schedule or to maintain a certain body weight and 8.9 percent drink as much as possible.

Nearly one-third of runners (29.6 percent) incorrectly believe they need to ingest extra salt while running and more than half (57.6 percent) say they drink sports drinks because the drinks have electrolytes that prevent low blood sodium. In fact, the main cause of low sodium in runners is drinking too much water or sports drinks.

Drinking too much fluid while running can cause a potentially fatal condition called exercise-associated hyponatremia that occurs when runners drink even when they are not thirsty which can dilute the sodium content of blood to abnormally low levels.

Symptoms of hyponatremia can include nausea, vomiting, headache, confusion, loss of energy, muscle weakness, spasms or cramps and in extreme cases, the condition can lead to seizures, unconsciousness and coma.

Source: Loyola University Health System