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03.27.07
Indication: Mortality risk
Source:
JAMA, February 28, 2007;297(8):842-57.
Research:
Antioxidant supplements are used for the prevention of several diseases, but researchers in this study set out to assess the effect of antioxidant supplements on mortality in randomized primary and secondary prevention trials. They searched electronic databases and bibliographies published by October 2005. All randomized trials involving adults comparing beta-carotene, vitamin A, vitamin C (ascorbic acid), vitamin E, and selenium either singly or combined vs. placebo or vs. no intervention were included in the meta-analysis. Randomization, blinding and follow-up were considered markers of bias in the included trials. The effect of antioxidant supplements on all-cause mortality was analyzed with random-effects meta-analyses and reported as relative risk (RR) with 95% confidence intervals (CIs). Meta-regression was used to assess the effect of covariates across the trials. In all, the researchers included 68 randomized trials with a total of 232,606 participants across 385 publications.
Results:
When all low- and high-bias risk trials of antioxidant supplements were pooled together there was no significant effect on mortality. Multivariate meta-regression analyses showed that low-bias risk trials and selenium were significantly associated with mortality. In 47 low-bias trials with a total of 180,938 participants, antioxidant supplements significantly increased mortality. In low-bias risk trials, after exclusion of selenium trials, beta-carotene, vitamin A, and vitamin E, singly or combined, significantly increased mortality. Vitamin C and selenium, however, had no significant effect on mortality. From these findings researchers believe treatment with beta-carotene, vitamin A and vitamin E may increase mortality, while the potential roles of vitamin C and selenium on mortality warrant further study.