Selenium and colorectal adenoma: Results of a pooled analysis

Background: Secondary analyses of data from a large randomized clinical trial have suggested that intake of the trace element selenium reduces risk of colorectal neoplasia, but epidemiologic studies have not shown a consistent protective association. Methods: We conducted a combined analysis of data from three randomized trials - the Wheat Bran Fiber Trial, the Polyp Prevention Trial, and the Polyp Prevention Study - which tested the effects of various nutritional interventions for colorectal adenoma prevention among participants who recently had an adenoma removed during colonoscopy. Selenium concentrations were measured from blood specimens from a total of 1763 trial participants, and quartiles of baseline selenium were established from the pooled data. To estimate the association between baseline selenium and colorectal adenoma risk, odds ratios (ORs) and 95% confidence intervals (Cls) were calculated using logistic regression modeling. All statistical tests were two-sided. Results: Individual study results among participants whose blood selenium concentrations were in the highest versus the lowest quartile varied in magnitude (Polyp Prevention Trial: OR = 0.67, 95% CI = 0.43 to 1.05; P_trend = .21; Wheat Bran Fiber Trial: OR = 0.66, 95% CI = 0.40 to 1.10; P_trend = .13, and Polyp Prevention Study: OR = 0.57, 95% CI = 0.34 to 0.95, P_trend = .04). Analyses of the pooled data showed that individuals whose blood selenium values were in the highest quartile (median = 150 ng/mL) had statistically significantly lower odds of developing a new adenoma compared with those in the lowest quartile (OR = 0.66, 95% CI = 0.50 to 0.87; P_trend = .006). Conclusions: The inverse association between higher blood selenium concentration and adenoma risk supports previous findings indicating that higher selenium status may be related to decreased risk of colorectal cancer.