Selenium is a mineral that is needed in small amounts by the body to help regulate the thyroid hormones and support a healthy immune system. One of selenium’s most important roles is as an antioxidant helping to prevent cell damage due to free radicals.
The selenium content of foods can vary widely depending on how much is in the soil where an animal is raised or a plant grown. The richest sources of selenium include seafood, meat, cereals and grains.
In the United States and Canada, animals that are cultivated for food, such as cows, pigs and chickens, are usually fed diets supplemented with selenium and thus, amounts in meats, milk and eggs tend to be relatively consistent. While the body more easily absorbs the selenium in plant sources than that in animal sources, fruits and vegetables vary greatly in their content. However, the large food-distribution systems in North America tend to even these differences out, therefore preventing low intakes in individuals living in selenium-poor areas.
Selenium deficiency is rare in the United States. Selenium deficiency itself is not thought to cause illness, but instead predisposes children and adolescents to two specific conditions, Keshan disease and Kashin-Beck disease. These diseases can affect the heart, bones and joints.
Selenium toxicity is rare in the United States. That said, high doses of selenium can be very toxic and high blood levels can result in a condition termed selenosis. The most frequently reported symptoms of selenosis include brittle hair and nails, gastrointestinal upset and hair loss. Other symptoms include garlic-breath odor, skin rash, fatigue, irritability and mild nerve damage.
The following table lists the recommended intake for healthy people based on current scientific information.