Are Multivitamin and Mineral Supplements Useful?

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.

COMMENT

In a strongly worded editorial, writers summarize the findings of 
these three studies by stating, “Most supplements do not prevent 
chronic disease or death, their use is not justified, and they should 
be avoided.” They do leave open the potential for a small benefit or 
harm in certain population subgroups.

Lamas GA et al. Ann Intern Med 
2013 Dec 17. Grodstein F et al. Ann Intern Med 2013 Dec 17. Fortmann 
SP et al. Ann Intern Med 2013 Dec 17. Guallar E et al. Ann Intern Med 
2013 Dec 17.

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