Some experts have suggested that dietary supplements have a “health halo,” a term that refers to consumers’ tendency to believe the products are “just vitamins” and, thus, harmless. However, a new study has uncovered that supplements sold after FDA recalls are still contaminated with banned pharmaceutical ingredients.

In a brief 3-page report published in the October 22, 2014 edition of JAMA, researchers from Harvard Medical School analyzed FDA class I drug recalls that targeted dietary supplements. The FDA mandates such recalls when products have the reasonable possibility of causing serious adverse health consequences or death.

According to the researchers, roughly half of all FDA class I drug recalls since 2004 have involved dietary supplements. Concerned that the contaminated products remain available on store shelves, the authors reviewed dietary supplements recalled over a 3-year period ending December 31, 2012, and available for purchase in July or August 2013.

Of the 27 recalled supplements that met the study’s inclusion criteria, the researchers determined 66.7% of them were still available for sale through the Internet, manufacturers, or retail locations for at least 6 months following the recall. Of the 20 that were produced by US manufacturers, 65% remained adulterated with banned ingredients. A full 22.2% of the supplements contained 1 or more additional banned ingredients not identified by the FDA.

Although the researchers limited their testing to adulterants commonly found in products with marketing claims of weight loss, sexual enhancement, and sports enhancement, they noted it is possible that the tested products contain other adulterants.

The study authors concluded that the FDA’s efforts have only partially eliminated potentially dangerous adulterated supplements from the US marketplace. To stem the flow of contaminated vitamins to consumers, they recommended aggressive enforcement of the law, expansion of the FDA’s enforcement powers, or both.