Selenium was discovered as an element in 1817 by the Swedish chemist Jöns Jacob Berzelius, who determined the atomic weights of many elements and developed a system of chemical symbols. Selenium is one of the essential nutrients for humans. Without it the heart, joints, eyes, immune system and reproductive system can suffer. Yet humans only need to eat a trace amount of selenium every day, about 55 micrograms.
Brazil nuts, seafood and organ meats are amount the richest dietary sources of selenium. The amount of selenium found in plant foods depends on the amount of it present in the soil were the plant was grown.
Selenium is an essential mineral found in small amounts in the body. It works as an antioxidant, especially when combined with vitamin E. Antioxidants like selenium help fight damaging particles in the body known as free radicals. Free radicals can damage cell membranes and DNA, and may contribute to aging and health conditions, including heart disease and cancer. Antioxidants can neutralize free radicals and may reduce or even help prevent some of the damage they cause.
Selenium plays a role in thyroid function. Your immune system also needs selenium to work properly.