Some herbal remedies may do more harm than good. Researchers writing today in the Journal of the American Medical Association report that 20 percent of herbal medicine products sampled contained dangerous levels of heavy metals.

Unlike prescription drugs, herbal medicine products can be sold as dietary supplements, which are not required to undergo rigorous testing before entering the marketplace. Indeed, the Dietary Supplement Health and Education Act (DSHEA) does not require proof of safety or efficacy. Robert B. Saper, now at Boston University's School of Medicine, and his colleagues purchased imported Ayurvedic herbal medicine products from stores near Boston's city hall and had them tested for metal contamination. They discovered that a fifth of the 70 samples tested contained lead, mercury or arsenic, or some combination of all three, in significant quantities. If taken as directed, the products would expose a person to more of the metals than is deemed safe by the Environmental Protection Agency.

"Although the prevalence of heavy metal-containing Ayurvedic [herbal medicine products] is unknown, the number of individuals at potential risk is substantial," the team writes. "Our findings support calls for reform of DSHEA that would require mandatory testing of all imported dietary supplements for toxic heavy metals."