DefinitionSelenium is an essential trace mineral. Small amounts of selenium are good for your health.Alternative NamesDiet - seleniumFunctionSelenium has a variety of functions. It helps make special proteins, called antioxidant enzymes, which play a role in preventing cell damage. Some medical information suggests that selenium may help prevent certain cancers, but better studies are needed.There have also been mixed results regarding selenium's impact on cardiovascular disease.Selenium seems to stimulate antibodies after you receive a vaccination. It also may help protect the body from the poisonous effects of heavy metals and other harmful substances.Selenium may boost fertility, especially among men. The mineral has been shown to improve the production of sperm and sperm movement.Food