Marathon dilemma: how much water is too much?

Interesting story on hyponatremia, a condition where blood sodium drops to a dangerous level, generally because the sufferer has been drinking too much water.

Last year, a 28-year-old died of it during the Boston Marathon, so this year the Red Cross stations will have scales available so runners can monitor their weight throughout the event. Runners going into hyponatremia retain more water than normal, so you'll be able to see a weight gain.

May be a justification for the various sports drinks, which typically have some sodium content. As does a banana.

From [Reuters Health eLine].