A recent study concluded that herbal supplements are often not what they claim to be. The study was published in the journal BMC Medicine and it got front-page coverage on the New York Times website.
Using DNA analysis, researchers tested 44 products from a dozen companies. The DNA signatures were compared with samples obtained from horticultural greenhouses.
The study was summarized in the New England Journal of Medicine Journal Watch for Psychiatry. The authors write –
More than half the products contained plant species not listed on the label, and one third had a product “substitution” (the advertised ingredient was not even present). One product labeled as St. John’s wort actually contained senna — a laxative. A ginkgo product was contaminated with a tree nut — dangerous for people with nut allergies. Another contaminant, feverfew, can react with warfarin and aspirin and increase the risk for bleeding.
The study authors point out that there are currently no standards for authenticating herbal products….
(For a study documenting that some Chinese herbal supplements are associated with risk for heavy metal poisoning, which causes a variety of psychiatric symptoms, see NEJM JW Psychiatry Mar 6 2002.)
These findings are particularly relevant to readers of this blog since large surveys of users of herbal supplements show that a high proportion of patients with depression and anxiety use them.
Caveat emptor – let the buyer beware. There are no standards for quality control of herbal products and essentially no monitoring of what gets put into them.
The only reliable resource for information about the quality of supplements is Consumer Lab, which does independent quality testing. You have to subscribe to get the results (that is how they pay for the testing) but I think that this study demonstrates that you should not be spending a lot of money on supplements if you don’t subscribe to Consumer Lab’s tests.