Washington: A fifth of ayurvedic medicines sold online were found to contain lead, mercury or arsenic above permissible levels, according to a recent study.

Ayurvedic preparations are used by many of India's 1.1 billion population and worldwide by people from South Asia, as well as others, says the study.

"However, since 1978 more than 80 cases of lead poisoning associated with ayurvedic medicine use have been reported worldwide," wrote the authors.

"Several Indian-manufactured rasa shastra medicines could result in lead and / or mercury ingestions 100 to 10,000 times greater than acceptable limits," they added in a study published in Wednesday's issue of the Journal of American Medical Association.

Ayurvedic medicines are of two major types - herbal and rasa shastra, which is an ancient practice of combining herbs with metals like mercury, lead, iron, zinc, minerals like mica and gems, mainly pearl.

Rasa shastra experts say that these medicines, if properly prepared and administered, are safe and therapeutic.

Robert B. Saper of the Boston University School of Medicine and his colleagues conducted the study to determine the prevalence of ayurvedic medicines available via the Internet containing lead, mercury or arsenic at detectable levels.

They also compared the prevalence of toxic metals between US and Indian-manufactured products, and in rasa shastra versus non-rasa shastra medicines.

The researchers conducted an Internet search using search terms ayurveda and ayurvedic medicine and identified 673 products, of which 230 preparations were randomly selected for purchase in August-October 2005.

Country of manufacturer / website supplier, rasa shastra status, and claims of 'good manufacturing practices' were recorded. Metal concentrations were measured using x-ray fluorescence spectroscopy. Of the 230 medicines requested, 193 were received and analysed.

Researchers found that the prevalence of metal-containing products was 20.7 percent and that the prevalence of metals in US 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 (midpoint) concentrations of lead and mercury.

Among the metal-containing products, 95 percent were sold by US websites and 75 percent claimed 'good manufacturing practices'. All metal-containing products exceeded one or more standards for acceptable daily metal intake.

"A 2005 Institute of Medicine report concluded that 'the regulatory mechanisms for monitoring the safety of dietary supplements (should) be revised'.

"New FDA regulations and current Indian policies do not specify any maximum acceptable concentrations or daily dose limits for metals in dietary supplements for domestic use," the authors wrote.

"We suggest strictly enforced, government-mandated daily dose limits for toxic metals in all dietary supplements and requirements that all manufacturers demonstrate compliance through independent third-party testing." IANS