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Ayurvedic herbal medicines and heavy metals

Study
Results
Comment

Bandolier just loves it when someone says that while alternative therapies may not have much evidence behind them, at least they do no harm. If only. Bandolier 104 reported that many herbal remedies “work” because they are adulterated with all sorts of drugs of low and high concentrations, and Chinese remedies for skin conditions commonly contain steroids. Bad things are known to happen because of this.

A study from Boston [1] examined Ayurvedic herbal remedies from south Asia and found that many contained high levels of the heavy metals lead, mercury, and arsenic.

Study

Researchers identified all the stores within 20 miles of Boston (Massachusetts, not Lincolnshire), and in mid-2003 visited the stores and bought one package of each Ayurvedic herbal remedy manufactured in south Asia and intended for oral use. No identical product was obtained more than once, but products with the same name but different manufacturer or different formulations were purchased. These were then analysed for lead, mercury, and arsenic.

Results

Seventy unique Ayurvedic products costing less than US$6 per package were obtained, manufactured in India or Pakistan, and carried in 30 stores. The most common indication for use was gastrointestinal disorders (70%).

Fourteen (20%) contained lead, mercury, and/or arsenic, some in very high concentrations. Figure 1 shows the concentrations found in micrograms (millionth of a gram, μg) per gram of herbal medicine. In Figure 1, the black horizontal bar represents the maximum recommended levels in some medicines in the USA, or the maximum chronic oral intake for mercury or arsenic, in micrograms. Concentrations of heavy metals in some herbal medicines were hundreds or thousands of times greater than this. Just to labour the point, please note that the concentrations in Figure 1 are on a logarithmic scale.



Figure 1: Concentration (logarithmic scale) of lead, mercury, and arsenic in Ayurvedic medicines (μg/g) in those medicines where it was detected. The horizontal black bars approximate maximum recommended levels of oral intake





Duplicate samples were obtained for the herbal medicines with high heavy metal concentrations, and gave almost identical results.

As well as lead, mercury, and arsenic, some herbal medicines also contained high concentrations of tin or silver, but not gold or cadmium. Some of the medicines were for use in children.

Comment

This is not the first report of heavy metals in Ayurvedic medicines, and the paper reviews some of the rich literature. It tells us that the heavy metal concentrations in the medicines, if taken at recommended doses, would provide sufficient to be toxic and that serious toxicity has been reported.

A review of traditional Indian remedies [2] shows that heavy metals, particularly lead, are regular constituents. This has repeatedly caused serious harm to patients taking such remedies. The incidence of heavy metal contamination was about 20% in this series [1], but the review found a study where 64% of samples collected in India contained significant amounts of lead (64% mercury, 41% arsenic and 9% cadmium). Both these papers have references to studies demonstrating heavy metal contamination of traditional Ayurvedic medicines. Ayurvedic principles apparently attribute important therapeutic roles to metals like mercury and lead, and these heavy metals have been the cause of significant illness.

There are two main lessons. The first is that knowledge that these medicines can contain high levels of heavy metals might make it worth asking patients with otherwise unexplained symptoms about their use. The other lesson is about testing and regulation. In a world that is so risk averse, how is it that people are allowed to purvey poisons to our fellows? The widespread notion of herbal medicinal products being inherently safe is at best naive and at worst downright dangerous.

Reference:

  1. RB Saper et al. Heavy metal content of Ayurvedic herbal medicine products. JAMA 2004 292: 2868-2873.
  2. E Ernst. Heavy metals in traditional Indian remedies. European Journal of Clinical Pharmacology 2002 57: 891-896.

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