The New York State Attorney General’s Office announced this week that it has issued cease-and-desist letters to four major retailers—GNC, Target, Walgreens, and Walmart—after testing several store brand herbal supplements and finding that only 21% of the tested products contained the ingredients stated on their labels. The attorney general’s findings also indicated that 35% of the tested products contained ingredients not declared on their labels. But several trade organizations representing the supplement industry, including the American Botanical Council, the American Herbal Products Association, the Council for Responsible Nutrition, and the Natural Products Association, have raised serious concerns about the testing methodology used by the attorney general and question whether the methodology has led to valid results. In particular, these groups state that:
The attorney general relied on a testing method called DNA barcoding, which looks for short DNA sequences to identify a particular plant species. However, DNA barcoding has been found to be highly unreliable when it comes to testing chemically complex, herbal extracts, since herbal extracts often contain insufficient or denatured plant DNA. Further, any herbal product that has been exposed to prolonged heat treatment or other processing may also damage DNA and therefore render the testing unreliable. So far, GNC has confirmed that every one of its products tested by the attorney general was indeed an extract.
The attorney general did not, it seems, verify the results from the DNA barcode testing with other types of tests, and did not run the plant materials through testing at other laboratories. Yet the most reliable way to confirm the identity of herbal ingredients is to use a range of appropriate methods, such as liquid chromatography and mass spectrometry, whenever possible.
The expert used by the attorney general to oversee the tests has a background in evolutionary biology, but does not appear to have any specialized expertise in botany, pharmacognosy (the study of natural product molecules for their medicinal or functional purposes), or natural product chemistry.
There are several other unanswered questions about the testing methodology, including, for example, what reference materials were used (i.e. official guidelines for identifying a particular plant species or its constituents) and specific details about how the sampling was conducted.
Because of these concerns, the trade organizations urge caution in assessing the results of the attorney general’s tests, and call for more information from the attorney general about the investigation; however, the attorney general’s office has stated that it will not release further information at this time. The trade organizations also remind consumers that supplements are generally safe, and that, despite claims to the contrary, the industry is highly regulated, with every manufacturer required by federal law to abide by rigorous Good Manufacturing Practices (GMPs).
Source: American Botanical Council, American Herbal Products Association, Council for Responsible Nutrition, Natural Products Association