Science - December 22, 2009

Asian herb mixtures may be poisonous

Traditional Asian herb mixtures may contain dangerous quantities of mercury, arsenic and lead. This is the contention of Ivonne Rietjens, professor of the Toxicology Department, and researchers of the Food and Consumer Product Safety Authority (VWA) in the coming issue of Food Additives and Contaminants.

The researchers examined the contents of 292 traditional herb mixtures from China, Tibet and India gathered from 2004 to 2007 which were sold as food supplement, medicine or herbal tea in nature food stores in the Netherlands. These can result in food poisoning.
Using a spectrometer, the researchers measured the levels of mercury, arsenic and lead. In twenty percent of the herb mixtures, the presence of these substances was indicated on the labels, but the measurements showed that 186 out of the 292 samples (64 percent) did actually have these harmful substances.
Twenty percent of the mixtures had such high concentrations of contaminants as to be harmful to health, adds Rietjens and the VWA researchers. Fifty products contained too much mercury; 26 products had too much arsenic and in eight mixtures, the permissible safety limit for lead was exceeded. One of the mixtures exceeded the permissible level of lead by 300 times.
The researchers plead for strict control of the products. Mercury, arsenic and lead are often added to herb mixtures for therapeutic reasons, but have been the cause of poisoning in users here and there in the world.
The Nutrition Centre issued a safety warning for traditional Asian herbal mixtures on 17 December. The VWA has published a list of unsafe herb mixtures on its site  and has withdrawn numerous products from the market. Since July 2009, European standards for mercury and lead in food supplements have been enforced, which allow the VWA to intervene, even when low concentrations of these heavy metals are detected.

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