Jamaluddin Moloo, MD, MPH

Two large, randomized trials and a meta-analysis all say no.

Do vitamin and mineral supplements really prevent disease? In two clinical trials and a meta-analysis, researchers evaluated the efficacy of dietary supplements.

In a double-blind trial, investigators evaluated whether oral multivitamins prevent adverse cardiovascular events in people with histories of myocardial infarction. More than 1700 patients (mean age, 65) were randomized to a 28-component, high-dose multivitamin and mineral supplement or to placebo. Only half of participants adhered to study preparations for at least 3 years. After a median follow-up of 4.6 years, incidences of recurrent adverse cardiovascular events were similar in the two groups (about 30%). In subgroup analysis of people who didn't take statins at baseline, event rates were lower in the supplement group than in the placebo group (hazard ratio, 0.62). No evidence of harm with vitamin use was reported.

In a second randomized study, researchers from the Physicians' Health Study II (NEJM JW Gen Med Nov 15 2012) examined the effects of multivitamin supplementation on cognitive function later in life. Male physicians (age, ≥65) received daily multivitamin or placebo supplements for a mean of 8.5 years; no difference was noted in change in cognitive function, as measured by five different cognition tests.

Finally, in an analysis for the U.S. Preventive Services Task Force, authors conducted a systematic review of studies that involved vitamin and mineral supplements for primary prevention of cardiovascular disease, cancer, or all-cause mortality among healthy individuals. No consistent evidence suggested a benefit from supplements. However, findings were limited by the small number of fair- and good-quality studies available for analysis of supplements other than β-carotene or vitamin E. For vitamin E, the researchers found good evidence of a null effect, whereas β-carotene was associated strongly with excess lung cancers and death among individuals whose risk for lung cancer was high.

Citation(s):

Lamas GA et al. Oral high-dose multivitamins and minerals after myocardial infarction: A randomized trial. Ann Intern Med 2013 Dec 17; 159:797.

Grodstein F et al. Long-term multivitamin supplementation and cognitive function in men: A randomized trial. Ann Intern Med 2013 Dec 17; 159:806.

Fortmann SP 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. Ann Intern Med 2013 Dec 17; 159:824.

Guallar E et al. Enough is enough: Stop wasting money on vitamin and mineral supplements. Ann Intern Med 2013 Dec 17; 159:850.