If you take herbal supplements, you may be getting more—or less—than you bargained for. In a study in BMC Medicine, DNA analysis of 44 herbal products found that most contained cheaper substitute species, contaminants, or fillers. Nearly 60 percent contained plant species not listed on the labels. For instance, one product labeled St. John’s wort instead contained Senna alexandrina, which can cause diarrhea and, if taken long-term, damage the colon. More than 20 percent had unlabeled fillers such as rice, soybeans, and wheat, which can be a concern for people with allergies to those foods.
Over the years studies have found that many dietary supplements are inaccurately labeled, but herbs are a special problem due to their complex chemistry and the difficulty in standardizing them. As a result, herbal supplements are “prone to contamination and possible product substitution,” the researchers said.
In early 2015, the New York Attorney General announced that DNA tests done for his office had found that 79 percent of herbal products contained little or none of the labeled substance—and often had inexpensive filler instead. Thus, he issued cease-and-desist letters to major retailers selling the products. He also announced that his investigation would continue and called for stricter FDA oversight. Several other attorneys general later joined in the probe. In response, industry experts said that such DNA testing is inappropriate for botanical products.
Until the data from these tests are published, it’s impossible to know the extent of the problem. Meanwhile, buyer beware.
Also see Supplement Claims: What's Allowed.