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St. John's Wort: What's Really in the Bottle

by Andrea Klausner, MS, RD  

If you take the herbal supplement St. John’s wort (Hypericum perforatum) for mild to moderate depression, be aware that many products are adulterated. Undeclared extracts from closely related plant species have been detected in numerous analyses over the years—added either intentionally or accidentally—according to the latest Botanical Adulterants Bulletin released by the American Botanical Council and two other nonprofit organizations.

Synthetic dyes, some possibly toxic or illegal, are also regularly found in the supplements, probably mixed in to throw off standard lab tests that are done for labeling purposes. In a 2016 analysis in the Journal of AOAC International, for example, 14 out of 37 samples (38 percent) were suspect.

St. John’s wort may raise levels of mood-enhancing neurotransmitters in the brain, similar to the way certain antidepressants work. But with increased demand in recent decades has come an increase in adulterated products that have chemical profiles significantly different from those of clinically proven extracts. “The co-occurrence of adulteration with dyes and other Hypericum species is an ongoing issue that must be addressed with appropriate quality control protocols,” the Bulletin concluded.

Anyone taking or planning to take St. John’s wort for depression should be under a physician’s care, since other treatment options may be more effective and since the herb can interfere with many medications including statins, warfarin (a blood thinner), digoxin (a heart drug), oral contraceptives, and certain HIV drugs. It also increases sun sensitivity. If you are already taking a prescription antidepressant, don’t switch to St. John’s wort on your own. And don’t combine the two.

Note also that studies do not support the use of St. John’s wort for severe depression, depression of long duration, or bipolar disorder. There is no good evidence that it relieves anxiety, seasonal affective disorder, insomnia, or premenstrual syndrome.

For the best assurance that you are getting what the label says is inside the bottle, look for seals from the nonprofit U.S. Pharmacopeial Convention (USP) or NSF International. The private company also has a certification program and, for a membership fee, you can see the complete lists of products that have passed or did not pass testing. In its latest analysis of 10 St. John’s wort products last September, 60 percent did not meet its quality criteria.

Also see St. John's Wort.