Antioxidant for immune system support. *Selenium is a natural antioxidant that delays the oxidation of polyunsaturated fatty acids and preserves the elasticity of tissue. Selenium is required for the production of certain prostaglandins, which promote healthy blood flow. In synergy with vitamin E, selenium promotes healthy growth and fertility, and improves the function of certain energy producing cells. Selenium also provides support for the immune system. Selenium protects normal cell function by supporting the body's natural defenses and scavenging harmful free radicals.