Essential mineral that works closely with vitamin E to produce antioxidants that neutralize the cell-damaging free radicals that can increase the risk of cancer and other diseases of aging. Breast, prostate, skin, lung, and gastrointestinal cancers are all inhibited by selenium. It appears to confer the greatest protection on men, and seems most effective against gastrointestinal cancer. The selenium in our diets comes from fish and shellfish, organ meats, such as liver, and some whole-grain cereals.