Worried you’re not getting enough nutrients? You may be among the 52 percent of American adults who use nutritional supplements—like echinacea, probiotics, fish oil, or multivitamins—to round out their diets. But these products may include more than consumers expect, according to new research examining the ingredients in many popular supplements.

“We were wondering, how well do labels represent what’s in the dietary supplement?” says study author Karen Andrews of the Nutrient Data Laboratory at the U.S. Department of Agriculture (USDA) in Beltsville, Maryland.

The work, published in The Journal of Nutrition, shows that many dietary supplement labels actually underestimate the amount of vitamins or minerals in the bottle. For example, adult multivitamins contained 40.5 percent more vitamin D, on