Scientific support for dietary supplements: A case study in conflicted science, serious harm, and poor post-market monitoring

Background: Dietary supplements are used by up to 73% of the US population, 4% of whom report experiencing adverse events. An estimated 15% of Americans use weight-loss supplements that often contain potent pharmacologically active ingredients. US Consumers generally assume products are safe and effective, and manufacturers may cite evidence to support such claims. But pre-market trials establishing safety and efficacy are not required in the US, and ingredients do not need to be GRAS (generally regarded as safe). By comparison, governments in Canada and Europe exercise greater regulatory control to protect the public from harm and inform them of effectiveness. There is evidence that weight-loss supplements can be harmful, and of industry efforts to build a body of scientific literature supporting product safety and effectiveness. Reliable post-market monitoring for adverse events is lacking in the US, and once such events are identified, previous experience with harmful supplements has shown US regulators to be less willing to intervene than their counterparts in Canada and Europe. This case study evaluates the influence of industry in studies of the top selling weight-loss supplement in the US, and the quality of post-market surveillance for adverse events associated with that product.

Methods: Pubmed searches using proprietary product names, reviews of product websites and FDA's Medwatch adverse events surveillance system.

Results: 26 unique published papers were located, 14 sharing one author employed by the manufacturer of the proprietary active ingredient. Papers by this author were generally more supportive of product safety and efficacy than papers by neutral authors. In 11 studies available for review, author's academic affiliation was noted in all 11, commercial affiliation in only 3, the product's commercial name was used in 9, product manufacturer noted in 6. No papers disclosed a funding source, though at least 2 received manufacturer funding. A single paper provided sufficient disclosure to identify the author as being affiliated with the manufacturer of the product being evaluated. A search of Pubmed located 8 published cases of severe adverse events associated with the product, including hepatoxicity, rhabdomyolosis and hypertensive retinopathy. No adverse event reports were located in Medwatch.

Conclusion: Weight-loss supplements may cause serious adverse events, and data supporting commercial claims lacks adequate conflict of interest disclosure. Limited pre-market safety requirements and poor post-market surveillance of dietary supplements in the US may endanger the public's health.