Lack of herbal supplement characterization in published randomized controlled trials.

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Am J Med. 2005 Oct;118(10):1087-93.

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Lack of herbal supplement characterization in published randomized

controlled trials.

Wolsko PM, Solondz DK, RS, Schachter SC, Eisenberg DM.

Kaiser Permanente Medical Group, Denver, CO 80020, USA.

pete.wolsko@...

PURPOSE: Herbal supplements in the United States and abroad have poor

quality control and high content variability. We assessed the extent

to which recently published randomized controlled trials of herbal

supplements characterized and verified the content of the supplement

under study. METHODS: We identified all MEDLINE-indexed English

language randomized controlled trials evaluating single-herb

preparations of echinacea, garlic, ginkgo, saw palmetto, or St.

's wort that were published between January 1, 2000, and February

9, 2004. From each article we extracted information characterizing

the herbal supplement studied. RESULTS: Of 81 randomized controlled

trials meeting inclusion criteria, 12 (15%) reported performing tests

to quantify actual contents, and 3 (4%) provided adequate data to

compare actual with expected content values of at least one chemical

constituent. In those 3 studies, actual content varied between 80%

and 113% of expected values. Studies of higher overall quality (Jadad

score > or =3) performed testing somewhat less frequently (5/54; 9%)

than those with lower Jadad scores (7/27; 26%) (P = .09). CONCLUSION:

Documented characterization of herbal supplements in published

randomized controlled trials is inadequate. Investigators may be

unaware of the extent to which herbal quality-control issues may

detract from the value of otherwise well-designed clinical trials.

The scientific and clinical utility of future herbal randomized

controlled trials would be enhanced if authors provided evidence that

the herbal products studied were of high quality.