Efficacy of Antioxidant Supplementation in Reducing Primary Cancer

January 10, 2008

Incidence and Mortality: Systematic Review and Meta-analysis

ADITYA BARDIA, MD, MPH; IMAD M. TLEYJEH, MD, MSC; JAMES R. CERHAN, MD, PHD; AMIT

K. SOOD, MD, MSC;

PAUL J. LIMBURG, MD, MPH; PATRICIA J. ERWIN, MLS; AND VICTOR M. MONTORI, MD, MSC

OBJECTIVE: To estimate the association between antioxidant use and primary

cancer incidence and mortality and to evaluate these effects across specific

antioxidant compounds, target organs, and participant subgroups.

METHODS: Multiple electronic databases (MEDLINE, Cochrane Controlled Clinical

Trials Register, EMBASE, Science Citation Index) were searched from their dates

of inception until August 2005 to identify eligible randomized clinical trials.

Random effects meta-analyses estimated pooled relative risks (RRs) and 95%

confidence intervals (CIs) that described the effect of antioxidantsvs placebo

on cancer incidence and cancer mortality.

RESULTS: Twelve eligible trials, 9 of high methodological quality, were

identified (total subject population, 104,196). Antioxidant supplementation did

not significantly reduce total cancer incidence (RR, 0.99; 95% CI, 0.94-1.04) or

mortality (RR, 1.03; 95%

CI, 0.92-1.15) or any site-specific cancer incidence. Beta carotene

supplementation was associated with an increase in the incidence of cancer among

smokers (RR, 1.10; 95% CI, 1.03-1.10) and with a trend toward increased cancer

mortality (RR, 1.16; 95% CI, 0.98-1.37). Selenium supplementation was

associated with reduced cancer incidence in men (RR, 0.77; 95% CI, 0.64-0.92)

but not in women (RR, 1.00; 95% CI, 0.89-1.13, valuefor interaction, P<.001) and

with reduced cancer mortality (RR, 0.78; 95% CI, 0.65-0.94). Vitamin E

supplementation had no apparent effect on overall cancer incidence (RR, 0.99;

95% CI, 0.94-1.04) or cancer mortality (RR, 1.04; 95% CI, 0.97-1.12).

CONCLUSION: Beta carotene supplementation appeared to increase cancer incidence

and cancer mortality among smokers, whereas vitamin E supplementation had no

effect. Selenium supplementation might have anticarcinogenic effects in men and

thus requires further research.

Mayo Clin Proc. 2008;83(1):23-34

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