Regardless of what’s printed on their product labels, many herbal supplements don’t contain all the ingredients consumers are paying money for.

A new study out of Canada found some producers of supplements skimp or omit altogether actual herbs and replace them with fillers, some of which can cause serious health problems for people with food allergies.

Using a DNA barcoding method, Canadian researchers tested 44 bottles of popular supplements sold by 12 companies in the United States and Canada and found that nearly 60% contained plant substances not mentioned on the product’s label, and one-third contained outright substitutions of the plant advertised on the bottle.

Instead, the products contained soybeans, wheat, rice and other fillers.

Some kinds of gingko biloba, which are consumed to improve memory, were mixed with black walnut—something a person with nut allergies would not want to ingest unknowingly.

Other popular herbs like St. John’s Wort and echinacea were also found to contain fillers. The echinacea included Parthenium hysterophorus, a plant that can cause rashes, nausea and flatulence. St. John’s Wort contained, in one instance, only rice, and in another instance Alexandrian Senna, an Egyptian shrub that acts as a powerful laxative and can cause liver damage.

Consumer advocates and scientists say the research shows that the herbal supplement industry—which makes $5 billion annually—needs to address these fraudulent practices.

“This suggests that the problems are widespread and that quality control for many companies, whether through ignorance, incompetence or dishonesty, is unacceptable,” David Schardt, a senior nutritionist at the Center for Science in the Public Interest, an advocacy group, told The New York Times. “Given these results, it’s hard to recommend any herbal supplements to consumers.”

A 1994 law allows herbal supplements to be marketed and sold with minimal regulatory oversight. The Food and Drug Administration only requires the manufacturers to ensure that their products are safe, and these products are assumed to be safe unless proven otherwise.

“If you had a child who was sick and three out of 10 penicillin pills were fake, everybody would be up in arms,” Stony Brook University’s Dr. David A. Baker, professor of obstetrics, gynecology and reproductive medicine who conducted a test of supplements, told the Times. “But it’s O.K. to buy a supplement where three out of 10 pills are fake. I don’t understand it. Why does this industry get away with that?”

-Noel Brinkerhoff, Danny Biederman

To Learn More:

Herbal Supplements Are Often Not What They Seem (by Anahad O’Connor, New York Times)

DNA Barcoding Detects Contamination and Substitution in North American Herbal Products (Steven G. Newmaster, Meghan Grguric, Dhivya Shanmughanandhan, Sathishkumar Ramalingam and Subramanyam Ragupathy, BMC Medicine)

Herbal Supplements Often Contain Unlisted Ingredients (by Rachael Rettner, Fox News)