Evidence on supplements is extremely limited: NIH.

The article focuses on the findings of the consensus panel of the National Institutes of Health on the lack of science behind the use of multivitamin and mineral supplements for the prevention of chronic diseases in the U.S. Most people assume that multivitamins and mineral supplements are safe, but scientists don not have the necessary evidence to give that assurance. The panel recommended more research and studies on the interactions of multivitamins and minerals with nutrients from food or from prescribed or over-the-counter medications. The panel also called for the new authority of the Federal Drug Administration to regulate supplements.