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Effects of vitamin treatment or supplements with purported antioxidant properties on skin cancer prevention: a meta-analysis of randomized controlled trials.
Chang, YJ, Myung, SK, Chung, ST, Kim, Y, Lee, EH, Jeon, YJ, Park, CH, Seo, HG, Huh, BY
Dermatology (Basel, Switzerland). 2011;(1):36-44
Abstract
AIMS: To investigate the effect of vitamin treatment or supplements with purported antioxidant properties on the primary and secondary prevention of skin cancer using a meta-analysis of randomized controlled trials (RCTs). METHODS We searched PubMed, Embase and the Cochrane Library in June 2009. Among 398 articles searched, 11 articles on 10 RCTs were included in the final analysis. RESULTS In a fixed-effects meta-analysis of all 10 trials, vitamin treatment or supplements with purported antioxidant properties were found to have no preventive effect on skin cancer [relative risk (RR) = 0.98; 95% confidence interval (CI) = 0.94-1.03]. Similar findings were observed in a subgroup meta-analysis of 10 studies on both primary prevention trials (RR = 0.98; 95% CI = 0.93-1.03) and secondary prevention trials (RR = 0.97; 95% CI = 0.83-1.13). Further, subgroup meta-analyses revealed no preventive effect on cancer by type of antioxidant, type of cancer and the methodological quality of the studies. CONCLUSION The current meta-analysis of RCTs indicated that there is no clinical evidence to support an overall primary and secondary preventive effect of vitamin treatment or supplements with purported antioxidant properties on skin cancer. The effect of vitamin supplements on skin cancer should not be overemphasized.
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Effects of antioxidant supplements on cancer prevention: meta-analysis of randomized controlled trials.
Myung, SK, Kim, Y, Ju, W, Choi, HJ, Bae, WK
Annals of oncology : official journal of the European Society for Medical Oncology. 2010;(1):166-79
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Abstract
BACKGROUND This meta-analysis aimed to investigate the effect of antioxidant supplements on the primary and secondary prevention of cancer as reported by randomized controlled trials. METHODS We searched Medline (PubMed), Excerpta Medica database, and the Cochrane Review in October 2007. RESULTS Among 3327 articles searched, 31 articles on 22 randomized controlled trials, which included 161 045 total subjects, 88 610 in antioxidant supplement groups and 72 435 in placebo or no-intervention groups, were included in the final analyses. In a fixed-effects meta-analysis of all 22 trials, antioxidant supplements were found to have no preventive effect on cancer [relative risk (RR) 0.99; 95% confidence interval (CI) 0.96-1.03). Similar findings were observed in 12 studies on primary prevention trials (RR 1.00; 95% CI 0.97-1.04) and in nine studies on secondary prevention trials (RR 0.97; 95% CI 0.83-1.13). Further, subgroup analyses revealed no preventive effect on cancer according to type of antioxidant, type of cancer, or the methodological quality of the studies. On the other hand, the use of antioxidant supplements significantly increased the risk of bladder cancer (RR 1.52; 95% CI 1.06-2.17) in a subgroup meta-analysis of four trials. CONCLUSIONS The meta-analysis of randomized controlled trials indicated that there is no clinical evidence to support an overall primary and secondary preventive effect of antioxidant supplements on cancer. The effects of antioxidant supplements on human health, particularly in relation to cancer, should not be overemphasized because the use of those might be harmful for some cancer.