Pregnant women who consume Ginkgo biloba may develop high levels of the toxin colchicine, which can damage fetuses, according to a recent study published in Chemical Research in Toxicology. But industry organizations and researchers have been quick to point out flaws in the study and are using independent lab test results to further discredit the research.
The toxic levels of colchicine in pregnant women were discovered during routine tests on placental blood from 24 pregnant women. Howard Petty, Ph.D., at Wayne State University in Detroit, co-author of the study, said he was surprised to find the toxin in five of the women's samples. Upon learning that the women with colchicine in their blood were taking dietary supplements, Petty and his team randomly tested herbal supplements and reported that a popular brand of ginkgo biloba contained the chemical. Based on their findings, the study's authors recommended that pregnant women avoid ginkgo and extended the warning to all herbal supplements.
Industry organizations have criticized the study and sponsored their own tests on ginkgo. Independent lab tests done by the Council for Responsible Nutrition, based in Washington, D.C., on five different ginkgo sources, including the one in the study, and analyzed by three different sources, found no traces of colchicine. Both the American Herbal Products Association, based in Silver Spring, Md., and the National Nutritional Foods Association, based in Newport Beach, Calif., initiated analysis of the top-selling ginkgo products but had not found one containing the toxin at press time.
"Let's be absolutely clear: Ginkgo does not naturally contain the alkaloid colchicine," said Joseph Betz, Ph.D., vice president for technical affairs at AHPA. "Since colchicine is not a constituent of the plant, its presence in the tested product, if confirmed, would either indicate contamination or adulteration of the product or of the laboratory equipment," he said. "Another strong possibility is that the researchers' analysis of their test results were seriously flawed."
The organizations also questioned the levels of colchicine reported to be present in the women's blood. "Even a cursory examination of the medical literature would have alerted the researchers that the levels they measured were well above the lethal level," said Jerry Cott, Ph.D., a neuropsychopharmacologist and former chief of the psychopharmacology research program at the National Institutes of Health, in an NNFA press release.
The CRN also took the study's authors to task for suggesting that dietary supplements are unregulated and not proven safe. "Ginkgo has been examined in more than 30 randomized, blinded, controlled studies and in more than 100 other clinical and pharmacological studies and found to be safe and efficacious, with no mention of colchicine," said John Cardellina, Ph.D., vice president, botanical and regulatory affairs at CRN. He also pointed out that warning statements, especially in regard to pregnancy and nursing, are included on most ginkgo labels.
Natural Foods Merchandiser volume XXII/number 10/p. 7