Selenium

Selenium is a trace mineral, not an antioxidant nutrient.  It is necessary for good health, but only a small amount is needed.  Selenium combines with proteins to create selenoproteins which are antioxidant enzymes.  Selenoproteins aid in preventing cellular damage caused by free radicals.

However, it is a component of antioxidant enzymes. Plant foods like rice and wheat are the major dietary sources of selenium in most countries. The amount of selenium in soil, which varies by region, determines the amount of selenium in the foods grown in that soil. Animals that eat grains or plants grown in selenium-rich soil have higher levels of selenium in their muscle. In the United States, meats and bread are common sources of dietary selenium. Brazil nuts also contain large quantities of selenium.

Some selenoproteins help control thyroid function and aid the immune system.

Plant foods are the main source of selenium in most countries. The amount of selenium depends on the selenium content of the soil where the plants are grown or animals are raised. Soils in the high plains of northern Nebraska and the Dakotas have very high levels of selenium. People living in those regions generally have the highest selenium intakes in the United States.  Food distribution across the country helps people living in low-selenium geographic areas from having low selenium intakes.

Selenium also can be found in some meats and seafood, because the animals eat grains or plants that have been grown in soil with higher levels of selenium. Meats, bread and nuts are common sources selenium.

Selenium deficiency is rare in the U.S. but can lead to the development of heart disease, hypothyroidism, and a weak immune system.  It can also make the body weaker and more susceptible to illnesses.

There are three diseases are caused by selenium deficiency:

• Keshan Disease - enlarged heart and poor heart function in children caused by a virus
• Kashin-Beck Disease - osteoarthropathy
• Myxedematous Endemic Cretinism - mental retardation

In the U.S., most cases of selenium deficiency are caused by severe gastrointestinal problems from Crohn's disease or the surgical removal of part of the stomach.