That has become increasingly evident to doctors, nurses, and disease trackers as reports have trickled in about cases of lead poisoning linked to Ayurvedic medications. In July, the US Centers for Disease Control and Prevention issued a detailed account of such cases, reporting that a dozen bouts of lead poisoning had been blamed on Ayurvedic remedies from 2000 through 2003. One of those cases was in Massachusetts. A middle-age man showed up at a Boston hospital in 2002 suffering seizures. Doctors were baffled. After running a battery of tests, they concluded that he had lead poisoning. 'The next obvious question is, why does he have lead toxicity?" said Dr. Robert B. Saper, lead author of the study published today. 'They asked him: 'Do you work with paint?' Finally, it was posed to the person whether he was taking anything other than conventional medicine. Lo and behold, he was taking an Ayurvedic herbal medicine product for the last six years to treat arthritis." The man, who had taken herbal tablets called Guglu, recovered. But in a textbook example of how clinical medicine can give birth to scientific research, Saper, then a fellow at the Osher Institute and now a Boston University researcher, heard about the case from colleagues and decided to study the presence of heavy metals in medicinal herbs. In high enough concentrations, such metals can result in serious complications -- including convulsions, nausea, and vomiting. From spring through fall 2003, Saper purchased 70 herbal medicine products imported from South Asia at 30 stores in the Boston area. The researchers did not examine Ayuverdic herbs made in this country. Samples were tested at a lab run by the US Environmental Protection Agency, with scientists hunting for the presence of possibly harmful amounts of lead, mercury, and arsenic. The finding: Fourteen of the herbal treatments -- 20 percent -- contained at least one of these heavy metals in unsafe concentrations. Researchers can't say for sure how the metals got there. Theories range from contamination during production to plants grown in tainted soil. But there also are suggestions in Ayurvedic textbooks that some metals may be added intentionally, valued for their reported healing potential. That is a possibility that does not alarm Subhash Sehgal, a Newbury Street gallery owner who has taken Ayurvedic medicines for most of his 53 years and insists they do not contain toxic levels of metal. To maintain his health, he eats bread each day that he coats with a gelatin called chayanprash, which is said to contain more than 12 herbs. 'It has been used for thousands of years, and we have never doubted it," he said. 'These are ancient ways to take care of your body." A 1994 federal law prohibited the FDA from regulating dietary supplements like prescription drugs, setting a high standard before such a product can be taken off the market. An FDA official said the agency could not comment on the Boston study until it receives all the data, but added that regulators are already working to more aggressively target supplements that have been shown to pose serious risk to consumers. Nearly a year ago, the FDA moved to ban ephedra, an herb that had been used by elite athletes to enhance performance by strengthening their muscles and by dieters to speed weight loss. Studies blamed the herb for 155 deaths. Saper advised patients taking imported Ayurvedic herbs to alert their doctors and consider testing for toxic substances. Michael McGuffin, president of the American Herbal Products Association, urged consumers not to lump domestically produced Ayurvedic herbs with imported products. 'And it's certainly too broad," McGuffin said, 'if it's read as a condemnation of all herbal products." Stephen Smith can be reached at stsmith@globe.com.