clinical events, all types of human studies are used (e.g., randomized controlled trials, prospective trials, case-control, and cohort studies). Data are abstracted from the literature and analyzed by independent reviewers with clinical and methodological expertise. The analysis includes an assessment of the internal validity and quality of the studies. The data analysis includes generation of evidence tables, graphical summaries, statistical tests, and meta-analyses. The results and conclusions of the analyses are summarized in an evidence report that contains conclusions on the current knowledge on the efficacy and adverse effects of the substance and provides recommendations for future research. Reports are available on the AHRQ website (

Nominations for clinical topics to be reviewed by an Evidence-based Practice Center are solicited through notices in the Federal Register. Topics must meet specific selection criteria including high incidence; significance for the needs of Medicare, Medicaid, or other federal health programs; high cost; controversy about effectiveness; and availability of scientific data. Based on this process, the dietary supplements milk thistle and garlic, in addition to over 70 other nondietary supplement topics, have been reviewed (AHRQ, 2002).


The U.S. Pharmacopeia-National Formulary (USP-NF) develops and provides standards of identity, strength, quality, purity, packaging, and labeling of drugs sold in the United States in the form of standards monographs; these standards monographs do not consider the inherent safety of the substance. The USP standards are recognized by Congress in the Federal Food, Drug, and Cosmetic Act of 1938 (21 U.S.C. § 321 et seq.) as the official compendium of the United States, making its established standards for drugs essentially similar to federal regulations (USP, 2002a). From its first publication in 1820, the USP contained monographs for hundreds of botanicals; however, most of them were removed by the end of the 1930s due to the changes in medical practices and the arrival of synthetic organic medicinal compounds in the U.S. marketplace. In 1990, in response to a USP Convention Resolution, the USP Committee of Revision, an independent body of elected scientific experts representing industry, academia, and government agencies, established public standards for vitamins, minerals, and their combination products. These standards monographs, along with general chapters that include manufacturing practices for nutritional supplements, were grouped together and published within a separate section of the USP called Nutritional Supplements.

In 1995, after passage of the Dietary Supplement Health and Education Act (DSHEA), the USP Convention, in recognition of the resurgence in the use of botanicals by the American public, adopted a resolution that encouraged the USP Committee of Revision to establish public standards for botanical dietary supplements. In response to the Convention resolution, the USP Committee of Revision generated a list of approximately 20 widely used botanicals for public standards monographs. Criteria for identification of these botanicals included lack of safety risk, extent of use by consumers, interest from regulatory agencies, positive assessment by recognized pharmacognosists, and the ability of the botanical to meet typical requirements for USP monographs. History of traditional use and pharmacological action were also considered. Standards monographs are not developed for botanicals that the USP believes may be associated with a significant safety risk (USP, 2000a, 2002b).

The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement