The nation's health-store shelves are groaning under the weight of herbal supplements. So someone must be buying the stuff. Researchers at Boston University School of Public Health checked out the trends in dietary supplements by calling people up and asking them what they use.

What the researchers wanted to know: What are the trends in dietary supplements?

What they did: From February 1998 to December 2002, 8,470 adults were interviewed by phone. The interviewers asked them about any medications or dietary supplements they'd taken in the last week, with a lot of extra questions to elicit anything they might have taken and forgotten about. Although single vitamins and minerals (vitamin C tablets, for example) are regulated by the Food and Drug Administration as dietary supplements, the researchers did not consider them in this study. Stuff like gingko biloba and St. John's wort is much more interesting.

What they found: Sixteen percent of respondents had used a dietary supplement in the past week. People who used dietary supplements were older and more likely to be female and white. They also had a higher average income and level of education. Young women were the least likely to be using dietary supplements. There are several examples of individual supplements' changing in popularity over time; for example, 4.1 percent of young men said they'd used ginseng in the past week in 1998–99, while only 2.1 percent used it in 2002. Less than 1 percent of people used lutein in 1998–99, but 8.4 percent used it in 2002. Lutein is an antioxidant that has been added to multivitamins since late 1999.

What the study means to you: Many of the herbal products were included in a multivitamin, so most people are probably not taking the supplements specifically to cure the common cold, cure cancer, or make themselves smarter. People should tell their doctors what herbal supplements they're taking, because even if they aren't regulated as drugs, herbs often work like drugs in the body and can have dangerous interactions with prescription drugs. But the researchers point out that, if people are taking herbs in a multivitamin, they may not be aware of what they're taking.

Caveats: The survey used random-digit dialing to reach people for the survey, a method that somewhat underrepresents lower-income people.

Find out more: Information about the labeling and regulation of herbal supplements from the Mayo Clinic—and how that relates to your safety

Read the article: Kelly, J.P. et al. "Recent Trends in Use of Herbal and Other Natural Products." Archives of Internal Medicine. Feb. 14, 2005, Vol. 164, pp. 281–286.

Abstract online: http://archinte.ama-assn.org