A recent study published in The Journal of the American Medical Association found heavy metals, including mercury, arsenic, and lead, in some ayurvedic herbs. The study tested two types of ayurvedic medicines—herbal only and rasa shastra. “Rasa shastra is an ancient science that uses metals and minerals in combination with herbs. These metals are then purified, so no heavy-metal content should exist,” says John Douillard, DC, PhD, ayurvedic practitioner in Boulder, Colorado. However, Douillard no longer feels confident that the purification process is effective. “It may be a lost science at this point.” While rasa shastra herbs were twice as likely to contain heavy metals, non–rasa shastra formulas also tested positive. Although there are no national laws to regulate the amount of mercury, lead, and arsenic in dietary supplements, Douillard says all should meet World Health Organization and American National Standards Institute criteria. Ayurvedic medicine is still a safe and effective way of treating illness. To make sure you’re getting the best herbs, Douillard recommends using only pure botanical formulas—plants that are dried and powdered—with five herbs or fewer. And familiarize yourself with the companies from whom you buy your herbs; those who test for heavy metals and other contaminants will happily tell you so.