The term “dietary supplement” has been defined by the Food and Drug Administration (FDA) as any product taken orally that contains an ingredient intended to supplement the diet.11 Therefore, dietary supplements may contain vitamins, minerals, herbs, amino acids, enzymes, and organ tissues, as well as metabolites, extracts, or concentrates of these substances. Dietary supplements constitute a rapidly growing sector of the US healthcare industry; $17.8 billion was spent on these products in the United States in 2001 alone, of which$4.2 billion was accounted for by herbal remedies.22 A 380% increase in the use of herbal products was reported between 1990 and 1997 in the United States.33

This relatively recent resurgence of interest in herbals has been attributed to the high cost of traditional western medicine, ready accessibility of botanical products, increased exposure...