Too Much Fluid Can Be As Bad As Too Little
July 17, 2003 -- Forget that advice to drink all you can before, during, and after exercise.
For water and for sports drinks, the new message is to drink wisely. Too many fluids are at least as dangerous as too few. But even though the USA Track & Field association changed its guidelines in April, the word hasn't reached everyone.
Most people still think you're supposed to drink as much as you can. But that advice is dead wrong, says Timothy David Noakes, MD, PhD, chairman of exercise and sports science at the University of Cape Town and the Sports Science Institute of South Africa. An authority on endurance sports, Noakes advises South Africa's national rugby and cricket teams. He's the author of Lore of Running, for years a bible to many serious runners.
"People have been coached to think that dehydration is the worst thing that can happen during exercise, so now you have a dangerous situation," Noakes tells WebMD. "A woman only needs to put on 2.5 kg of fluid to kill herself. It adds up real quickly -- it is easy to get overloaded. It is frightening how easily it can happen."
It's often said that by the time you get thirsty, you've waited too long to take a drink. Nonsense, Noakes says.
"The idea that thirst comes too late is a marketing ploy of the sports drink industry," Noakes says. "They tell people their thirst is not giving them right information. There is absolutely no biological information that is correct. The answer is just drink what your thirst dictates."
The Beginning of Bad Advice
In an editorial in the July 19 issue of the British Medical Journal, Noakes notes that from ancient times until 1969, people didn't drink during exercise. Then an influential -- and, Noakes says, error-filled -- scientific paper concluded that this led to dangerous overheating. Soon after, the first sports drinks hit the market, and advertising encouraged people to drink all the fluids they could.
That still wasn't a problem, until amateur running became popular. Elite athletes don't have time to drink too much. It's a totally different story when people run/walk marathons over five hours.
"They are running so slowly they can drink all they want," Noakes says. "There is no place outside of a pub where fluids are so available as in a marathon in the U.S. And unlike a pub, you aren't limited by having to pay for it. It doesn't take much to get fluid overload."