Vitamins may pose a more serious health risk than ultra-bright urine.
The National Institutes of Health called for more oversight of the $23 billion dietary supplement industry.
“The product with which we're dealing is virtually unregulated," Dr. J. Michael McGinnis of the Institute of Medicine, who led the NIH panel's review, told the Associated Press.
Doctors working on the study urged consumers not take supplements that exceed 100 percent of the recommended daily amount (RDA). "Why would I take 53 times what people tell me is the RDA?" William Vaughan of Consumer's Union asked the AP.
Additionally, some vitamins can interact with medications in negative ways.
Cornell University nutritionist Patsy Brannon told the AP that too much niacin can cause liver damage, too much vitamin A can cause birth defects and too much vitamin E can cause bleeding problems.
According to the study, the people who can most benefit from taking multi-vitamins are the least likely to take them.
A daily multivitamin is a great way to fill gaps in nutrition; however, scientists strongly urge consumers to follow RDA guidelines when using other supplements.