No Clear Evidence for Role of Selenium in Cancer Prevention

Selenium exposure may be associated with reduced risk of cancer but evidence inconclusive

MONDAY, May 16 (HealthDay News) -- Selenium exposure has no clear effect on cancer incidence, and supplementation does not seem to prevent cancer, according to a review published online May 11 in the Cochrane Database of Systematic Reviews.

Gabriele Dennert, M.D., from the Institut für Transdisziplinäre Gesundheitsforschung in Berlin, and colleagues investigated the relationship between selenium and cancer risk and prevention in women and men. Literature searches identified 49 prospective observational studies, which were used to assess the association between selenium exposure and cancer risk, and six randomized controlled trials (RCTs), which they used to investigate the efficacy of selenium supplementation on cancer prevention.

The investigators found a decreased incidence of cancer (summary odds ratio [OR], 0.69) and mortality (OR, 0.55) with increased selenium exposure. The reduction was more pronounced in men than women (incidence OR, 0.66; 95 percent confidence interval 0.42 to 1.05; versus 0.90; 95 percent confidence interval 0.45 to 1.77). Study design, and quality and heterogeneity of the data, complicated interpretation of the statistics. There was no evidence from RCTs of a protective efficacy of selenium yeast supplementation against non-melanoma skin cancer, or L-selenomethionine supplementation against prostate cancer. Results for the prevention of liver cancer were inconsistent, and results from other trials indicated that selenium supplementation may have harmful effects.

"No reliable conclusions can be drawn regarding a causal relationship between low selenium exposure and an increased risk of cancer. Despite evidence for an inverse association between selenium exposure and the risk of some types of cancer, these results should be interpreted with care," the authors write.

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