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By Lisa Collier Cool in Yahoo Health
Jul 23, 2012
For years, athletes and the public have been told to prehydrate before exercise, "drink ahead of thirst," and train their gut to tolerate far more fluid than their brain thinks they need to avoid the dangers of dehydration. As sports-drink companies are pitching their products as performance boosters in ads timed for the Olympics, startling new research in the British Medical Journal (BMJ) throws cold water on many of their claims.
Seven scathing new BMJ reports investigate everything from the sports-drink industry's financial ties to scientists who study hydration to what researchers call "a striking lack of evidence to support the vast majority of claims related to enhanced performance or recovery."
The researchers also contend that much of the science behind sports drinks is biased or inconclusive and that empty calories from sports drinks are major contributors to childhood obesity and tooth decay. The investigation concludes that dehydration has been overblown into a "dreaded disease of exercise," due to fear mongering by marketers, rather than solid, independent science.
Biased Science Spreads False Fear
An accompanying commentary by investigations editor Deborah Cohen states, "An investigation by the BMJ has found that companies have sponsored scientists, who have gone on to develop a whole area of science dedicated to hydration," spreading often groundless "fear about the dangers of dehydration."
The American College of Sports Medicine accepted a $250,000 donation from Gatorade in 1992. Four years later, the college developed new guidelines adopting a "zero percent dehydration" rule telling athletes to "drink as much as tolerable," Cohen reports. The guideline originated in a 1993 roundtable meeting supported by Gatorade, according to Atlantic Monthly.
Ad Claims Lacking in Research
In one of the BMJ studies, researchers from the Centre for Evidence-Based Medicine at the University of Oxford examined 431 ads making performance-enhancing claims about 104 sports products, including sports drinks.
For more than half of the advertized claims made, the researchers found no studies on the websites listed in the ads to support the claims. GlaxoSmithKline was the only company that provided the BMJ with a list of studies attesting to the benefits of sports drinks, but the publication identified a number of flaws in their methodology.
The researchers concluded that, "only three (2.7%) of the studies the team was able to assess were judged to be of high quality and at low risk of bias." Overall, they found that 85 percent of scientific studies cited by manufacturers to support claimed performance-enhancing benefits of their products have a very high risk of bias (such as research sponsored by the company).
Undermining a Natural Body Signal: Thirst
During the first New York marathon, in 1970, Cohen reports, "marathon runners were discouraged from drinking fluids for fear that it would slow them down."
The BMJ investigation contends that one of the "greatest successes" of the Gatorade Sports Sciences Institute, established in 1985, was "to undermine the idea that the body has a perfectly good homeostatic mechanism for detecting and responding to dehydration-thirst." Instead the mantra became that thirst was a dangerously unreliable indicator of hydration, and sales of sports drinks quickly soared to a $2 billion industry in the US.
BMJ analyzed current hydration guidelines for marathon runners and found that, "drinking according to the dictate of thirst throughout a marathon seems to confer no major disadvantage over drinking to replace all fluid losses, and there is no evidence that full fluid replacement is superior to drinking to thirst."
An earlier study by the same researchers compared runners who did three two-hour workouts, in which they either quaffed a sports beverage according to thirst (about 13 oz. per hour), at a moderate timed rate (about 4 oz. every 15 to 20 minutes) and at a high rate (about 10 oz every 15 to 20 minutes). There were no significant differences in core body temperature or finishing time.
"The idea that thirst comes too late is a marketing ploy of the sports-drink industry," says Tim Noakes, M.D., professor of sport and exercise science at University of Cape Town, South Africa, and author of the BMJ study.
Sports Drinks and Childhood Obesity
BMJ also reports that sports drink companies, including Gatorade, have school outreach programs that encourage kids to swig their products during exercise. The investigation also reports that studies either directly funded by or involving authors with financial ties to the sports drink industry make claims designed to worry parents and sell more sports drinks, such as, "children are particularly likely to forget to drink unless reminded to do so."
Because these high-calorie drinks are promoted as part of fitness, parents and kids often view them as much healthier than other sugar-laden beverages. The American Academy of Pediatrics, however, warns that sugar in sports drinks contributes to both obesity and tooth decay in kids.
"The way sports beverages have been marketed to children is astonishing. They're almost seen as an essential part of participation in sports, when the best beverage for a child participating in any physical activity is just plain water," Dr. Goutham Rao, clinical director of the Weight Management and Wellness Center at Children's Hospital of Pittsburgh told ABC News.
Experts say that to need an electrolyte-replenishing sports drink, kids need to have been exercising at high intensity, and sweating heavily, for at least 90 minutes. And even then, an 8-ounce drink should usually be ample to replace lost fluids.
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