Medical researchers say that one-fifth of Ayurvedic herbal medicines sold on the Internet contain dangerously high levels of lead, arsenic and mercury, according to a study published in the Aug. 27 issue of JAMA.

Ayurvedic supplements, which are said to be based on traditional Indian medicine, are used by the majority of India's 1.1 billion residents, as well as by people worldwide. However, an analysis by Boston researchers found that there have been 80 cases of lead poisoning associated with the supplements over the past 30 years.

Ayurvedic medicines are divided into two major types: herbal-only and rasa shastra, which is an ancient practice of deliberately combining herbs with metals such as mercury, lead, iron and zinc, as well as minerals such as mica and gems like pearl.

The researchers conducted an Internet search using the search terms Ayurveda and Ayurvedic medicine and identified 673 products, of which 230 Ayurvedic medicines were randomly selected for purchase between August and October 2005.

Metal concentrations were measured using x-ray fluorescence spectroscopy. One hundred ninety-three of the 230 requested medicines were received and analyzed.

Dr. Robert B. Saper, of Boston University School of Medicine and Boston Medical Center, and colleagues found that the prevalence of metals in U.S.-manufactured products was 21.7 percent, compared with 19.5 percent in Indian products.

Rasa shastra medicines were more than twice as likely as non–rasa shastra products to contain detectable metals and had higher median concentrations of lead and mercury. Among the metal-containing products, 95 percent were sold by U.S. Web sites and 75 percent claimed "good manufacturing practices."

All of the metal-containing products exceeded one or more standards for acceptable daily metal intake.

"Several Indian-manufactured rasa shastra medicines could result in lead and/or mercury ingestions 100 to 10,000 times greater than acceptable limits," the authors wrote in their study.

The authors suggested greater government oversight as to how much metal is allowed to be used in the supplements.

Click here for more on this study published in JAMA.