In the journals: Herbal supplements often not what they claim to be

Herbal supplements often contain undisclosed substances, suggests a study in BMC Medicine. Researchers scanned the DNA of a random selection of 44 herbal products from 12 companies. The products frequently contained ingredients other than those listed on the labels—including some that a buyer would probably want to know about.

• One-fifth of the products contained unlisted fillers like ground-up soybeans or rice powder.

• One-third of the products contained plants totally unrelated to the ones the product said it contained. In one instance, an herbal supplement labeled as St. John's wort—used by some people as a mild antidepressant—actually contained the laxative senna.

• Some products were contaminated with material derived from black walnut plants, which could be dangerous to people with nut allergies.

The presence of substitutions, nut contaminants, and fillers makes it more likely that consumers could experience unpleasant or even dangerous side effects. "These activities dilute the effectiveness of otherwise useful remedies, lowering the perceived value of all related products because of a lack of consumer confidence in them," the study authors wrote.