Two studies included in the review found lower overall cancer incidence in men who took a multivitamin for over 10 years. Those same studies showed no cancer protection benefit for women.
Researchers caution that these results should not be overgeneralized and that more research is needed before it can be determined whether or not multivitamin supplementation is beneficial. The evidence review was conducted by researchers for the United States Preventive Services Task Force (USPSTF) to update its previous recommendation. In 2003, the USPSTF found insufficient evidence to recommend for or against the use of vitamins A, C, and E, multivitamins with folic acid, or anti-oxidant combinations for the prevention of cardiovascular disease or cancer.
At the time, the USPSTF recommended against beta-carotene supplements alone or in combination with other supplements because they had no benefit and actually harmed patients at risk for lung cancer. The current research review reconfirmed the beta-carotene findings and also found good evidence that Vitamin E does not protect against cancer or cardiovascular disease.
Citation: Stephen P. Fortmann, MD; Brittany U. Burda, MPH; Caitlyn A. Senger, MPH; Jennifer S. Lin, MD, MCR; and Evelyn P. Whitlock, MD, MPH, 'Vitamin and Mineral Supplements in the Primary Prevention of Cardiovascular Disease and Cancer: An Updated Systematic Evidence Review for the U.S. Preventive Services Task Force', Ann Intern Med. 2013;159(12):824-834-834. doi:10.7326/0003-4819-159-12-201312170-00729