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Yet, Catlin says the take-home message is that unregulated over-the-counter supplements may contain many unadvertised impurities. When Catlin's team tested seven different brands of andro, they found that actual amounts of andro differed from what advertisers claimed, and one dose contained testosterone, which is illegal, he reports.

"What dietary supplement customers are buying isn't always what they are getting," he says. "This is a case where the buyer must beware."

Andro has been alleged to increase muscle size and strength, and the supplement garnered headlines two years ago when baseball slugger Mark McGuire admitted using it. While Major League Baseball is reviewing the product, the National Collegiate Athletic Association, the National Football League, the National Gym Association, the North American Boxing Federation, and professional tennis have banned the supplement.

Despite the controversy, the FDA allows andro and related products to be sold over the counter at health food stores, gyms, and grocery stores.

"We've seen a large rash of athletes testing positive for 19-norandrosterone in the last few years," Catlin says. "Many claimed they didn't take anything, but later admitted that they'd used andro or something similar."

Cynthia Kuhn, PhD, of Duke University Medical Center in Durham, N.C., reviewed the report for WebMD. She says the levels of nandrolone found in the andro capsules are not enough to be medically hazardous. But the important point is that actual contents of the supplements differ from what is advertised, she tells WebMD.

"This has been often speculated, but rarely tested," says Kuhn, who is professor of pharmacology in the department of pharmacology and cancer biology, and has written a book about supplements. "What is in these supplements is not what the advertisers say, and there are trace elements that can cause athletes trouble."

She says, "These supplements are drugs, even if people don't think of them as drugs."

The National Institutes of Health, the NFL, NCAA, U.S. Olympic Committee, Major League Baseball, and the Major League Baseball Players Association supported the study by Catlin's group at UCLA.

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