Here is an article from this morning's NY Times about over-hydration.
Brain-Dead From Sports Drinks
For years now, we've been hearing about the importance of hydration to avoid heat stroke during prolonged exercise in hot weather. Now, it turns out, too much hydration can kill you.
A study published today in The New England Journal of Medicine should give weekend warriors reason to rethink the wisdom of quaffing vast amounts of water or sports drinks while exercising vigorously - at least if they are engaging in such endurance tests as a marathon. The study found that a marathon runner could dangerously dilute the blood with an overdose of liquids, risking a coma and even death. The problem has also been detected during long military maneuvers, extended bike rides and blistering hikes through the desert.
An article by Gina Kolata in The Times today describes the slow and belated recognition of the problem. A South African expert who has been warning of the dangers for more than two decades told Ms. Kolata that he had not found a single case when an athlete had died from dehydration in a competitive race, but that some people had sickened and died from drinking too much. Typically, an overdose of water dilutes their blood and reduces the concentration of sodium. Water enters the cells, causing them to swell, and engorged brain cells press into the skull; such pressure can lead to confusion, seizures and a loss of vital functions.
All too often, friends, coaches or emergency personnel assume that the problem is dehydration and administer yet more liquid, making the problem worse. The best treatment is a small volume of a concentrated salt solution, given intravenously, to increase blood sodium concentrations. Sports drinks containing electrolytes may not help much as they are mostly liquid themselves.
In the 2002 Boston Marathon, for example, a 28-year-old woman found herself exhausted after running for five hours and gulping sports drinks along the way. Wrongly assuming that she was dehydrated, she chugged down 16 more ounces of a sports drink. She promptly collapsed and was later declared brain-dead. The concentration of salt in her blood was found to be lethally low.
In the study published today, researchers at various Harvard-affiliated institutions tested 488 of the nearly 15,000 runners who completed the 2002 Boston Marathon. They found that 13 percent had blood with abnormally low sodium levels, and that three runners were in danger of dying. It was not the elite runners who were at risk - it was those who had taken four hours or more to finish the race, allowing plenty of time to imbibe excess fluid.
Sports authorities have already issued warnings and tips to avoid excessive drinking, and rescue workers in the Grand Canyon now carry devices to test collapsed hikers for low blood sodium. But the solution is for overly eager endurance runners and hikers to forget the old mantra that they should drink-drink-drink. Too much liquid can be lethal.
