Researchers unveiled results showing that resveratrol, an antioxidant found in grape skins, wine, and peanuts, barely enters the human bloodstream when taken by mouth.
Laboratory studies have shown that the chemical can kill cancer cells or inhibit their growth. But without remaining in the blood, researchers say the drug is highly unlikely to exert any effect on breast cancer, prostate cancer, or heart disease as many marketers claim.
Still, dozens of dietary supplements and other products available in health food stores tout the chemical for its anticancer properties.
"To really believe that a biological effect can occur is to find that the drug circulates in the plasma of the body. We didn't find any," says Thomas Walle, PhD, a professor of pharmacology at the Medical University of South Carolina.
Walle and his colleagues gave resveratrol to six healthy adult volunteers between the ages of 23 and 29. The chemical was tagged with a radioactive marker known as Carbon-14, which allows researchers to later detect it in tissues and blood. The study was funded by the National Cancer Institute.
But when the researchers later checked blood for the radioactive signature, none was found.
"It's difficult to assume now that it would have any effect against heart disease, prostate cancer, and breast cancer," says Walle, who presented his study in Washington at the Experimental Biology 2004, a meeting of several scientific groups including the American Society of Pharmacology and Experimental Therapeutics.
David Bylund, PhD, professor of pharmacology at the University of Nebraska, said that Walle's conclusion is "correctly stated." "This [chemical] is disappearing very rapidly. Unless you're going to be taking it every hour, it probably wouldn't be able to do any good," he tells WebMD.
But Bylund says the chemical may still be used to synthesize other, related compounds that may stay in the body for a longer time. Those derivatives would have to be tested as drugs under FDA rules and not sold as dietary supplements, he says.
Still 'A Very Exciting Compound'
"I think the consumer is in trouble here," Walle tells WebMD, referring to the numerous products and Internet claims touting resveratrol for its anticancer properties.
But other preliminary findings show that the chemical can accumulate in the cells of the digestive tract and the human airway. That means the resveratrol could theoretically exercise its anticancer properties in the colon, esophagus, trachea, or throat.
"For this compound there are some very interesting activities observed. It's a very exciting compound," Walle says.
His group is currently returning to the lab to see if resveratrol can inhibit cancer in epithelial cells from the human digestive tract and throat.