A systematic review of published studies found insufficient evidence that vitamin and mineral supplements are effective for the prevention of CVD, cancer or related mortality.
Researchers for the US Preventive Services Task Force evaluated studies on this association that were published from 2005 to January 2013. The analysis focused on 26 studies on the benefits and harms of individual or paired supplements and multivitamin supplementation. Supplements in the studies included beta-carotene, vitamin E, selenium, vitamin C, folic acid, vitamin D and calcium.
Two large trials covering 27,658 participants found lower cancer incidence in men taking a multivitamin for more than 10 years (pooled unadjusted RR=0.94; 95% CI, 0.89-1). However, one of those trials did not include women, and the other found no effect in women.
Twenty-four studies covering 324,653 participants showed no clear evidence of benefit or harm. There was no evidence that vitamin E or beta-carotene prevented CVD or cancer, but the researchers found evidence that beta-carotene increased risk for lung cancer in smokers. Sample sizes were small for other supplements.
“We found no consistent evidence that the included supplements affected CVD, cancer or all-cause mortality in healthy individuals without known nutritional deficiencies,” the researchers wrote. “The certainty of this result is tempered, however, by the fact that few fair- or good-quality studies are available for all supplements except vitamin E and beta-carotene.”
Despite these limitations, “the current literature on single or paired vitamins and minerals is sufficient to discourage additional studies of beta-carotene or vitamins A, C and E in general populations not deficient in the nutrients,” the researchers wrote. “Future studies of selenium should clearly separate individuals with adequate and low baseline selenium levels. Future studies of vitamin D should be done separately from studies of calcium. Vitamin D and calcium studies should include a full range of hypothesized benefits, including fracture prevention, to allow a comprehensive comparison of overall benefits and harms.” – by Joan-Marie Stiglich
Disclosure: The researchers report no relevant financial disclosures.