Evidence-Based Indications for Herbal Supplements Ignored

IOWA CITY, May 10 -- Most users of herbal supplements are doing it for anything that ails them, ignoring specific claims of efficacy, however tenuous, found investigators here.

Most users are oblivious to the intended scientific use of specific herbal products, a use documented by at least one so-called evidence-based study, said Aditya Bardia, M.D., M.P.H., of the University of Iowa, now at the Mayo Clinic in Rochester, Minn.

Of the 30,617 adults surveyed by the annual National Health Interview Survey (NHIS), 5,787 (18.9%) consumed herbs in the past 12 months, and of these, 3,315 (57.3%) used an herbal supplement to treat a specific health condition, the investigators reported in the May issue of the Mayo Clinic Proceedings.

Among those who used only one of four popular herbs, approximately one-third used it for a condition for which a study suggested some benefit.

Women (OR 1.81), older persons, non-Hispanic whites, and people with a college education (1.55) were more likely to use herbs on the basis of what they perceived as scientific merit.

Adults younger than 60 and black adults (OR 0.51) were significantly less likely than their counterparts to use herbs for purportedly appropriate indications.

The study had several limitations. All information was self-reported and respondents who used more than one herb were excluded because the study was not designed to evaluate multiple drugs use.

Finally, they said, because the survey provided no information on specific products or dosages, there was no way of knowing whether those who took the herbs, even according to allegedly appropriate indications, took them at the recommended schedules and dosages.

These five supplements evaluated were garlic (high cholesterol level), ginseng (diabetes), kava-kava (anxiety), soy (high cholesterol, source of protein, hot flashes), and St. John's wort (depression).

This work was made possible by a grant from the National Institute of Environmental Health Sciences and the Office of Dietary Supplements, National Institutes of Health. No financial conflicts were reported.