updated 12:41 a.m. ET Aug. 3, 2005

BALTIMORE - Depending on whom you ask, Rafael Palmeiro’s claim that he unwittingly took something to cause a positive test for steroids is either plausible — or laughable.

The lack of regulation and testing of nutritional supplements lends credence to the claims of players who say they were caught unaware by positive tests, one researcher said Tuesday.

Steroid building blocks known as prohormones can cause a positive test — and may not be listed on supplement labels, said Anthony C. Tommasello, a professor and director of the Office of Substance Abuse Studies at the University of Maryland pharmacy school in Baltimore.

“Some are extracts of natural products that are also metabolized into anabolic hormones but the substances are not on the banned list,” Tommasello said.

One such ingredient is DHEA, Tommasello said. Mostly manufactured in China from the dried roots of a wild yam, it is a popular muscle-building supplement in the United States. While not on Major League Baseball’s list of banned substances, it is converted in the body into an anabolic steroid, Tommasello said.

Weakening the plausibility of Palmeiro’s claims was a report that the Orioles slugger tested positive for stanozolol, a powerful anabolic steroid not available in dietary supplements. The report, posted late Tuesday on the Web site of The New York Times, cited a person in baseball with knowledge of the drug-testing program who requested anonymity because the sport prohibits disclosure about test results without authorization.

Stanozolol is known by the brand name Winstrol, most notably linked to the Olympic sprinter Ben Johnson of Canada, who was stripped of his 100-meter gold medal in 1988.

Even if Palmeiro was just taking the so-called precursors and knew about it, it’s akin to steroid use, said Adrian Dobs, an endocrinologist and professor of medicine at Johns Hopkins University in Baltimore. “These people aren’t dumb. They know what they are doing,” she said.

Palmeiro — who testified before a congressional panel in March that he “never used steroids” — became baseball’s highest-profile player to serve a 10-game suspension Monday after testing positive for a performance-enhancing drug. And while he didn’t deny turning in a positive test, the slugger was adamant that it was an accident.

“When I testified in front of Congress, I know that I was testifying under oath and I told the truth,” he said during a telephone conference call Monday. “Today I am telling the truth again that I did not do this intentionally or knowingly.”

Palmeiro’s test was taken some weeks after he testified before Congress in March, meaning he is probably not at risk for perjury, the Times reported, citing a committee staff member who spoke to the newspaper on condition of anonymity because official statements are supposed to come from members of Congress.

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At least one member of baseball’s management-union medical panel initially found there was a “reasonable basis” for Palmeiro’s claims, as evidenced by the delay in his penalty.

But the notion that a legal, nonprescription supplement could cause a positive test for steroids doesn’t make sense to David R. Seckman, executive director of the National Nutritional Foods Association, which represents the supplement industry.

While looking over baseball’s list of banned substances, Seckman was unequivocal in saying that the average nutritional supplement store “isn’t selling those type of products.”

“Those are steroids. They are controlled substances,” Seckman said. “You can only get those with a prescription.”

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