A systematic review finds limited evidence of benefit.
Researchers from Kaiser Permanente Center for Health Research in Portland, Oregon systematically reviewed the literature addressing the benefit and harms of vitamin and mineral supplements in community-dwelling, nutrient-sufficient adults for the primary prevention of cardiovascular disease and cancer. They reviewed trials and observational studies that had good to high levels of evidence and were published between January 2005 and January 2013. After screening 12,766 abstracts and reviewing 277 full-text articles, they included 103 articles (26 studies) in their analysis.
The study sizes ranged from 128 to 72,337 participants with average ages ranging from 22 to 77 years. Six of the studies were conducted among women only, five were conducted among men only, and the remaining were studies of men and women. The effects of the supplements were examined between 6 months and 16 years; most studies provided less than a decade of follow-up.
Two large trials reported lower cancer incidence in men taking a multivitamin for more than 10 years; however, a study that included women showed no effect of multivitamin intake. High-quality studies of single and paired nutrients (such as vitamins A, C, or D; folic acid; selenium; or calcium) were scant and heterogeneous and showed no evidence of benefit or harm. Neither vitamin E nor β-carotene prevented cancer, and β-carotene increased lung cancer risk in smokers.
Fortmann SP, Burda BU, Senger CA, et al. 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. Annals of Internal Medicine; published online 11/12/13. Available at http://annals.org/article.aspx?articleid=1767855.