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
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
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