Relation of Vitamin E and Selenium Intakes to Prostate Cancer Risk by Smoking Status: A Review and Meta-Analysis Open Access

Kim, Yeunjung (2013)

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Both observational studies and clinical trials have investigated the association between antioxidants and prostate cancer risk. However, reports on the efficacy of antioxidants, namely selenium and vitamin E, in reducing the risk of prostate cancer have shown no clear benefit. It has been noted that smoking status may modify this effect of antioxidants through a variety of mechanisms. In this study, we performed a review of the literature and meta-analysis to examine the associations of vitamin E and selenium with prostate cancer in three groups of participants: never smokers, former smokers and non-smokers. In total, 20 studies met the inclusion criteria and provided necessary data. Summary analyses produced overall meta-relative risk (RR) estimates for vitamin E of 0.99 [95% confidence interval (CI), 0.90-1.09] in never smokers, 0.97 (95% CI, 0.90-1.04) in former smokers, and 0.94 (95% CI, 0.72-1.23) in current smokers. For selenium studies, overall meta-RRs were 1.09 (95% CI, 0.78-1.53), 0.63 (95% CI, 0.45-0.87) and 0.84 (95% CI, 0.57-1.25) for never former and current smokers, respectively. Most sensitivity analyses using subgroups of studies with different exposure assessment methods and outcome definitions produced null results that did not differ appreciably in smokers and non-smokers. The only possible exception is the analysis of studies that relied on serum selenium, which produced ORs (95% CIs) of 1.08 (0.75-1.56), 0.79 (0.65-0.95), and 0.75 (0.56-1.00), respectively, for never, former and current smokers. The interpretation of overall summary analyses is limited by small number of observations, varying definitions of smoking status, and methodological limitations of the available studies. Nevertheless, the findings for serum selenium are noteworthy and may require additional evaluation.

Table of Contents

Table of Contents

I. Introduction p1

II. Materials and Methods p4

III. Results p7

IV. Discussion p10

V. References p14

VI. Tables and Figures p19

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