Risk of taking an artificial multivitamin Results from many clinical trials show that beta-carotene, vitamin E, and possibly high doses of vitamin A can increase the risk of premature death. Other studies have linked multivitamin use to increased cancer risk , and iron supplements can be harmful to people who don't need them. A 2013 editorial in the Annals of Internal Medicine found that daily multivitamins don't prevent chronic disease or death, and their use can't be justified — unless a person is below science-based requirement levels. Mega-doses of vitamins A, D, E, and K can cause health problems, says Consumer Reports, and may interfere with other prescription medications people are taking. Too much vitamin A (in its retinol form) may lead to liver failure or even death , while pregnant women may risk birth defects. Dietary supplements, such as over-the-counter multivitamins , do “more harm than good” and can increase the risk of developing cancer