With great interest, we read the research letter by Philips and colleagues1 and the invited commentary by Shekelle2 regarding the safety of dietary supplements, specifically, Enzyte (Vianda, LLC, Cincinnati, Ohio). Both contributions review safety concerns and the lack of evidence of product benefits. We praise the authors for this effort, as certainly a dearth of unbiased information regarding the safety of dietary supplements exists.3 However, many concerns surround research with dietary supplements and some are limitations of this study.4 We restrict our discussion to the area of supplement quality and do not review other possible study limitations. We believe that the issue of product content particularly should be highlighted. The report fails to mention or document actual product content vs label claims or potential variability, an important limitation that flaws much of the research on dietary supplements published to date and limits the applicability of conclusions.
Glisson JK, Minor DS, Walker LA, Gurley BJ. Dietary Supplements: Safety Issues and Quality Control. Arch Intern Med. 2011;171(5):476-477. doi:10.1001/archinternmed.2011.53