St. John's Wort Supplements Review

A DNA study that suggested widespread problems with herbal supplements has been retracted. Get the details in our St. John’s Wort Supplements Review.

A DNA analysis of herbal supplements in 2013 suggested that many contained plants not listed on labels. However, some of those findings seem to have been made-up, according to a recent investigation. For details, see the update in the St. John’s Supplements Review.

A recent analysis found adverse reactions associated with St. John's wort were similar to those reported for the prescription SSRI antidepressant fluoxetine (Prozac), and serious adverse reactions were most likely to occur when the herb was taken in addition to a prescription drug. Get the details, plus more about concerns and potential drug interactions and our tests of popular supplements in the St. John's wort Supplements Review >>

St. John's wort is known to interact with a large number of prescription drugs. That number grew larger recently when the FDA approved two new drugs to cure hepatitis C infection. Taking these drugs while using St. John's wort may lead to reduced therapeutic effect and is not recommended. More information about this and other drug interactions with St. John's wort is found in the "Concerns and Cautions" section of the St. John's Wort Supplements Review >>

DNA analysis of 44 herbal products from Canada and the U.S. found that only 48% contained the herb listed on the label and one-third of these products contained contaminants or fillers not listed on the label (Newmaster, BMC Med 2013). Nine percent of products contained only rice or wheat and none of the listed herb. Many cases of herb substitution were reported, including senna (a laxative) in a product labeled as St. John's wort. Several products were contaminated with feverfew, which should not be consumed by pregnant women and may react with a variety of medications. The researchers, from the University of Guelph in Ontario, did not disclose the identities of the tested products, which were single-ingredient herbs sold as capsules, powders, or tablets. Significant challenges continue to exist for routine use of DNA analysis of herbs, but ConsumerLab.com may use this technique where appropriate in the future, alongside other analytical techniques in its Product Reviews.