Selenium is a mineral found in soil, water, and some foods. It is important for making many body processes work correctly.
Most of the selenium in the body comes from the diet. The amount of selenium in food depends on where it is grown or raised. Crab, liver, fish, poultry, and wheat are generally good selenium sources. The amount of selenium in soils varies a lot around the world, which means that the foods grown in these soils also have differing selenium levels. In the U.S., the Eastern Coastal Plain and the Pacific Northwest have the lowest selenium levels. People in these regions naturally take in about 60 to 90 mcg of selenium per day from their diet. Although this amount of selenium is adequate, it is below the average daily intake in the U.S., which is 125 mcg.
Selenium is used for selenium deficiency, a disease that causes underactive thyroid (autoimmune thyroiditis), and high blood pressure during pregnancy. It is also used for diseases of the heart and blood vessels, including stroke, complications from statin drugs, and abnormal cholesterol levels, as well as for many other conditions.
Selenium is important for making many body processes work correctly. It seems to increase the action of antioxidants.