A new study finds that higher levels of selenium in the blood may be associated with a decreased risk of colorectal cancer.

Selenium is a trace element found in meats and grains, but dietary intake can vary by geographic area because of different concentrations of the element in the soil. People living in regions where selenium intake is low have higher rates of several cancers, including colorectal cancer. In addition, secondary analyses of data from a large randomized clinical trial suggested that selenium intake reduces the risk of colorectal cancer, but epidemiologic data has not found a consistent association.

Elizabeth T. Jacobs, Ph.D., of the Arizona Cancer Center in Tucson, and colleagues pooled data from three randomized trials--the Wheat Bran Fiber Trial, the Polyp Prevention Trial, and the Polyp Prevention Study--to assess the effect of selenium levels in the blood on colorectal adenoma recurrence.

Trial participants who were in the highest quartile for blood selenium levels had a 34% decreased risk of developing a new adenoma compared with participants in the lowest quartile. The researchers conclude that these results support previous findings that higher levels of selenium in the blood may be associated with a decreased risk of colorectal cancer.

In an editorial, Scott M. Lippman, M.D., of the University of Texas M. D. Anderson Cancer Center in Houston, and colleagues discuss possible biologic mechanisms for this association, including selenium's effects on gene promoter methylation and polyunsaturated fatty acid metabolism.

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