Is Selenium Effective for Cancer Prevention?
By Alan R. Gaby, M.D. Selenium functions as an antioxidant and also enhances immune function, effects that might be expected to protect against the development of cancer. Numerous animal studies have shown that selenium has an anticancer effect.[1] Observational studies in humans have also found that better selenium status is associated with a lower incidence of cancer. In some clinical trials, selenium supplementation decreased the risk of developing cancer, but a recent double-blind trial did not find a protective effect. These studies are reviewed below, and possible explanations for the conflicting findings are offered. In a region of China where the incidence of primary liver cancer is high because of polluted water, aflatoxin exposure, and a high rate of hepatitis B infection, selenium supplementation (200 mcg per day) significantly decreased the incidence of liver cancer compared with placebo. Selenium supplementation also significantly decreased the incidence of liver cancer in
