Some herbal supplements are being adulterated with plants not listed on the label, including top allergens like walnut, wheat and soy, according to a new study published in BMC Medicine.
“Herbal manufactures have not had easy access to DNA barcoding technology, so we should not expect them to know what is in the raw materials they are purchasing,” says Steven Newmaster, lead study author and botanical director of the Biodiversity Institute of Ontario at the University of Guelph, in Canada. DNA barcoding works by taking a “fingerprint” or barcode of the plant’s DNA, which is unique to each plant.
Researchers used DNA barcoding to analyze 44 North American herbal products, which are typically used to help alleviate a wide array of issues from poor memory to colds, depression and arthritis, and found that 59 percent contained plant species not listed on the label. Researchers compared the barcode derived from the herbal product with one derived from the known plant species to see if they matched. In many cases, they did not.
Some products were found to contain filler materials in addition to the plant matter they were supposed to contain, while others did not appear to contain the plant listed on the label at all.
Of significant concern for those living with food allergies or celiac disease, some herbal products were adulterated with top allergens: both soybean and wheat were found to be used as fillers. Yet exactly how much was present, whether it was protein (the allergenic part of a plant) and would cause a reaction was not examined.
In one case, black walnut was discovered in a Ginkgo product. The study authors believe, however, it is much more likely that leaves from walnut trees were unintentionally added, as opposed to walnut itself. They note that these leaves contain juglone, which has been shown to promote tumors.
The study authors stress that this was a small-scale study, and that it does not necessarily reflect the state of the natural health products industry as a whole. The study looked at fewer than 1 percent of the herbal products available on the market, from fewer than 5 percent of the companies that sell such products.
But scale aside, the significance of the findings is drawing media attention, including The New York Times. Another concerning contaminant was feverfew, an invasive weed from Europe and Asia, which can bring side effects like numbness of the mouth, oral ulcers, nausea and vomiting.
Feverfew can also trigger contact dermatitis and it can react negatively with certain medications, and pregnant women are never supposed to consume it. As well, a product labeled as St. John’s Wort, which is used to treat depression, was instead found to contain senna, a herbal laxative.
Next: Why the contamination?