Unlike prescription medications, dietary supplements aren't reviewed or approved by the FDA before they go on sale. And, although manufacturers have been required to prove that new supplements are "reasonably expected to be safe" since 1994, a recent report in the New England Journal of Medicine found that this law is largely unenforced.
"Consumers have the idea that the people who are selling herbal remedies are doing it out the goodness of their hearts," says Lauren Streicher, assistant professor of obstetrics and gynecology at Northwestern University's Feinberg School of Medicine. But supplement makers are even more profit-driven than pharmaceutical companies, which are subject to FDA review, she says. "Does the FDA make mistakes? Yes. But they're the only protection we've got to make sure greed doesn't get in the way of science." [Read more: 4 Herbal Supplements Your Doctor Hates]
Angela Haupt is a health reporter for U.S. News & World Report. You can follow her on Twitter or reach her at email@example.com.