Lack of herbal supplement characterization in published randomized controlled trials.
OBJECTIVE
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. John'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).


CONCLUSIONS
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.
Wolsko
Peter M
PM
Kaiser Permanente Medical Group, Denver, CO 80020, USA. pete.wolsko@uchsc.edu
Solondz
David K
DK
Phillips
Russell S
RS
Schachter
Steven C
SC
Eisenberg
David M
DM
D004340:Drug Contamination; D020900:Echinacea / Q000737:chemistry; D005737:Garlic / Q000737:chemistry; D020441:Ginkgo biloba / Q000737:chemistry; D006801:Humans; D020902:Hypericum / Q000737:chemistry; D008517:Phytotherapy; D010936:Plant Extracts / Q000737:chemistry; D028321:Plant Preparations / Q000737:chemistry*; D011786:Quality Control; D016032:Randomized Controlled Trials as Topic; D028024:Serenoa / Q000737:chemistry
D010936:Plant Extracts; D028321:Plant Preparations; C040972:saw palmetto extract