The study was conducted by researchers from the Biodiversity Institute of Ontario at the University of Guelph and the findings have been published in the journal BMC Medicine. The paper is titled “DNA barcoding detects contamination and substitution in North American herbal products.”
For the research, the group examined 44 herbal products produced by 12 manufacturers and sold in the U.S. and Canada. The analysis found that 59 percent of those products contained DNA barcodes from plant species not listed on their labels, and a third of the products contained undeclared contaminants and fillers. In their paper, the researchers noted that substituting ingredients and adding filers can dilute the otherwise helpful activities of certain plant species.
As an example the research team found that a sample labelled as St John’s Wort was actually substituted with extract of the plant Senna alexandrina. This is an FDA-approved herbal laxative, and is not recommended for prolonged use as it can cause side effects such as chronic diarrhoea and liver damage. Other products were contaminated with Parthenium hysterophorus, a type of plant commonly known as feverfew, which has side effects including numbness of the mouth and nausea, and can heighten the risk of bleeding when taken with blood-thinning medicines such as Warfarin.
Commenting on the findings, Graham Lord, director of the U.K.’s National Institute for Health Research Comprehensive Biomedical Research Center, told New Scientist magazine: “The level of regulation of herbal products is not good enough. It’s an intelligent idea that the authors suggest to use DNA barcoding to determine purity and really get to grips with the provenance.”
The research did not indicate whether or not a herbal remedy is effective; the study looked into the claims of “purity” made by the manufacturers of the products.