WASHINGTON -- What athletes take in may dry them out. Carbonated drinks and hamburgers can wind up causing dehydration, experts say.
Sugary, caffeine-packed soft drinks, in particular, can cause trouble, said Dr. Gary I. Wadler of New York University School of Medicine. A cola's sugar and the carbonation can make a person feel full without providing enough liquid.
''They are very sweet, so you get bloated. They are gaseous, so they distend you, so you get more bloated,'' Wadler said. And caffeine, which tends to increase the flow of urine, ''is a double whammy,'' he said. ''You lose on all counts.''
Former tennis star Jimmy Connors used to be one of Wadler's patients.
''He used to get these horrific total body cramps. It was sort of a mystery,'' Wadler said. ''I found out he was drinking cola drinks in great quantity, and he was getting bloated. Because he was bloated, he was not drinking adequate fluids.''
The risk is not limited to sodas, researchers say. Protein breakdown requires water, and the protein in a couple of hamburgers can leave people dehydrated, a researcher said.
''We didn't have to make them sweat,'' said nutrition researcher Catherine Jackson who conducted a dehydration study. ''The hamburger meat was enough.''
Although her study did not measure athletic performance, the amount of dehydration would have been enough to make an endurance athlete perform worse, said Jackson, who works at California State University, Fresno, and is also spokeswoman for the American Dietetic Association. The study was conducted to help NASA develop rehydration fluids for astronauts. It was published as a NASA internal memo in 1992.
Time spent sleeping also leaves people dehydrated, so the researchers had their test subjects eat the burgers before bedtime, to make the dehydration worse.
A separate study presented last month in New Orleans at Experimental Biology 2002, a conference of seven research-oriented professional societies, found that athletes who took in more protein wound up more dehydrated.
''The concern is that increasing protein increases the work the kidney has to do, and can impact the amount of fluid needed to get rid of waste,'' said researcher Nancy Rodriguez of the University of Connecticut.
That study, led by graduate student William F. Martin, examined five members of the university's track team. The athletes were placed on supervised high-, medium- and low-protein diets. All the athletes spent a month on each level. ''We fed them everything they ate for the four weeks of the diet,'' said Rodriguez, senior author of the preliminary report.
The low-protein diet worked out to about 68 grams a day for a 150-pound person; the medium-protein, to 123 grams, and the high-protein, to 246 grams.
The low protein diet was mostly grains, augmented by some beef and dairy foods, Rodriguez said. The medium-protein diet was equivalent to the level that athletes -- and most Americans -- normally have, she said. The high-level diet was mostly meat, supplemented by nutrition bars to add to the protein intake, she said.
The high level would be very unusual, but not uncommon for body builders, football players and others trying to add muscle, Rodriguez said.
The athletes also got bottled water, and filled out forms each day on how much water they drank, Rodriguez said. ''I was very conscious of keeping them hydrated,'' she said.
As the amount of protein rose, the athletes' kidneys had to work harder as the body tried to get rid of the excess protein, the study found. There was a higher proportion of protein breakdown chemicals such as nitrogen in the urine of athletes on the high-protein diet.
The researchers took those findings as signs that athletes on high-protein diets were losing more water. And because there was no evidence the athletes were drinking more, the scientists concluded the men were dehydrated.
It doesn't take much dehydration to reduce an athlete's ability to perform. Being about 1 percent below optimal fluid level can reduce exercise performance. Rodriguez said her study did not test performance because testing could have impaired the athletes' readiness to compete.
But the athletes did not notice being more thirsty, and did not report drinking more, as their protein levels rose, the study found.
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