In the last few months, there has been much talk in the media regarding the purity of herbal supplements. How should one advise patients interested in using these products?

Herbal supplements are not closely regulated by the Food and Drug Administration (FDA) due to the 1994 Dietary Supplement Health and Education Act. As a result of this, herbal products are not routinely tested for safety, efficacy, purity, or to verify that they contain the ingredients stated on the label.

A 2013 study showed that one-third of herbal products tested using DNA barcoding contained plants or other contaminants not listed on the label.1 Only 2 of 12 companies tested in this study had products without any contaminants or unlabeled substitutions or fillers. More recently, the New York State attorney general’s office tested herbal supplements sold at four major US retailers and found that 4 of 5 supplements tested using DNA barcoding did not contain the herbs listed on their labels.2 Representatives from the supplement industry have argued against using this method of testing to verify ingredients; however as of this writing, results from alternate methods of testing performed by the industry have not yet been reported.

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When speaking with patients about these products, it is important to advise patients of the potential risks of taking herbal supplements, such as lack of regulation and potential interactions with their chemotherapy, their cancer, or other medications. Patients should review all supplements with a health care provider before taking them during cancer treatment. Patients should be aware that the products they use may not contain the ingredients stated on the label, and that doing so is “at your own risk.” The United States Pharmacopeia (USP) is an independent group that verifies that herbal supplement ingredients are present in stated amounts, so patients who wish to take these products should consider purchasing products with the USP seal on their labeling.


1. Newmaster SG, Grguric M, Shanmughanandhan D, et al. DNA barcoding detects contamination and substitution in North American herbal products. BMC Medicine. 2013;11:222.

2. O’Connor A. New York attorney general targets supplements at major retailers. New York Times. February 3, 2015. Accessed April 2, 2015.