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Evidence summaries

Antioxidant Supplements and Mortality

Antioxidant supplements appear not to decrease mortality in healthy people or patients with chronic diseases. Beta carotene and vitamin E may increase the risk of death, and so may higher doses of vitamin A. Level of evidence: "B"

A Cochrane review [Abstract] 1 included 78 studies with a total of 296 707 subjects. Overall, the antioxidant supplements had no significant effect on mortality in a random-effects meta-analysis (RR 1.02, 95% CI 0.98 to 1.05), but significantly increased mortality in a fixed-effect model (RR 1.03, 95% CI 1.01 to 1.05). In 56 low-bias trials the antioxidant supplements significantly increased mortality (RR 1.04, 95% CI 1.01 to 1.07). In low-bias risk trials beta carotene (RR 1.05, 95% CI 1.01 to 1.09) and vitamin E (RR 1.03, 95% CI 1.00 to 1.05) significantly increased mortality, whereas vitamin A (RR 1.07, 95% CI 0.97 ti 1.18), vitamin C (RR 1.02, 95% CI 0.98 to 1.07), and selenium (RR 0.97, 95% CI 0.91 to 1.03) did not significantly affect mortality. In univariate meta-regression analysis, the dose of vitamin A was significantly associated with increased mortality (RR 1.0006, 95% CI 1.0002 to 1.001, P = 0.002).

Comment: The quality of evidence is downgraded by inconsistency (variability in results across studies).

    References

    • Bjelakovic G, Nikolova D, Gluud LL et al. Antioxidant supplements for prevention of mortality in healthy participants and patients with various diseases. Cochrane Database Syst Rev 2012;(3):CD007176. [PubMed].

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