Selenium and cancer:
A multicenter, double-blind, randomized, placebo-controlled trial of 1,312 patients with a history of basal cell cancers (BCC) or squamous cell cancers (SCC) and a mean follow-up of 6.4 years showed that 200 mcg of selenium failed to decrease the development of skin cancer and may increase the risk of BCC (by 10%) and SCC (by 14%) compared to placebo. However, the results also indicated that with supplementation, total cancer incidence was decreased by 37% (77 in the selenium group compared to 119 in the control group), total cancer mortality was decreased 50% (29 in the selenium group compared to 59 in the placebo group), and prostate cancer incidence was decreased by approximately 50% compared to placebo. There was also a lower incidence seen in lung and colorectal cancers but this finding was not statistically significant. (29)