"Most clinical trials that support the efficacy of herbals are financed by their manufacturers. Critical reviews of the quality of those clinical trials reveal serious limitations, including small sample size, short study duration, and lack of allocation concealment or double-blinding. In addition, most of these studies fail to disclose the source of funding and the identity of those who analyzed the data. Despite these shortcomings, many reviews conclude that the clinical trial data are inconclusive but "promising." Evaluation of therapeutic agents also requires an assessment of risks. Data on the toxicity of herbals are very limited because adverse events are evaluated only by patient self-reports and because clinical trials lack monitoring of hepatic or renal function." (The reliability of the Natural Standard as a source of evidence-based indications is also questioned.) Donald M. Marcus, MD , Baylor College of Medicine, Houston, Texas, and Arthur P. Grollman, MD, State University of New York at Stony Brook (Mayo Clinic Proceedings, November 2007)