The medicines, often mixes of herbs and supplements based on traditional, popular health treatments in India, need to be policed and strictly regulated, medical researcher Robert Saper said.
"Since 1978 more than 80 cases of lead poisoning associated with Ayurvedic medicine use have been reported worldwide," Saper and colleagues wrote in a newly published study on Ayurvedic applications sold over the Internet.
"This study highlights the need for Congress to revisit the way dietary supplements are regulated in the US."
"Our first priority must be the safety of the public. Herbs and supplements with high levels of lead, mercury, and arsenic should not be available for sale on the Internet or elsewhere."
The study notes that there are two types of Ayurvedic medicines: one using only herbs and another, called rasa shastra, in which herbs are mixed with metals like mercury, lead, iron, zinc, and other materials like mica and pearl.
Advocates of rasa shastra medicines say they are safe.
But the study led by Saper found that, of 193 samples of both types of Ayurvedic medicines bought on the Internet during 2005 and tested using x-ray fluorescence spectroscopy, 20.7 percent contained metals, all of them in amounts exceeding some standards of acceptable daily metal intake.
They noted that rasa shastra medicines were twice as likely to have metals as non-rasa shastra products. They also said that the US-manufactured Ayurvedic medicines were slightly more likely to have metals content than Indian products, 21.7 percent versus 19.5 percent.
However, they added, "Several Indian-manufactured rasa shastra medicines could result in lead and/or mercury ingestions 100 to 10,000 times greater than acceptable limits."
Study co-author Venkatesh Thuppil, Director of the National Referral Centre for Lead Poisoning in India, warned about the Ayurvedic products.
"The medicines which are supposed to cure sickness should not promote another illness due to the presence of toxic materials such as lead," Thuppil said.
Saper, of the Boston University School of Medicine, and co-authors of the study, which was published in the August 27 issue of JAMA, called on the government to set "strictly enforced, government-mandated daily dose limits for toxic metals in all dietary supplements."
They also said Ayurvedic manufacturers should be required to provide their products for independent third-party testing to ensure compliance with the rules.