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Selenium Deficiency

What is Selenium Deficiency?

Selenium is a trace mineral needed by the body in small amounts for good health. It is incorporated into proteins to make selenoproteins, which are important antioxidant enzymes. The antioxidant properties of selenoproteins help prevent cellular damage from free radicals that can cause the development of chronic diseases such as cancer and heart disease. Other selenoproteins help regulate thyroid function and play a role in the immune system.

Selenium deficiency, although rare, occurs when the body does not have enough selenium.

Cause of Selenium Deficiency

Plant foods are the major dietary sources of selenium in most countries throughout the world. The content of selenium in food depends on the selenium content of the soil where the plants are grown. Selenium also can be found in some meats and seafood. Animals that eat grains or plants that were grown in selenium-rich soil have higher levels of selenium in their muscles. Bread and some nuts are also common sources of dietary selenium. In general, people in the U.S. have an adequate intake of selenium. Soils in some parts of the world, such as China and Russia, have very low amounts of selenium. Selenium deficiency is often reported in those regions because most food in those areas is grown and eaten locally.

Symptoms of Selenium Deficiency

Selenium deficiency can lead to Keshan disease. The main symptom of Keshan disease is myocardial necrosis, leading to weakening of the heart. Selenium deficiency also contributes to Kashin-Beck disease. Kashin-Beck disease results in atrophy, degeneration, and necrosis of cartilage tissue in the joints. The body also becomes more susceptible to illness caused by other nutritional, biochemical, or infectious diseases.

A selenium deficiency can cause symptoms of hypothyroidism, including extreme fatigue, mental slowing, goiter, mental retardation, and miscarriages.

Diagnosis of Selenium Deficiency

Diagnosis is generally made clinically. High levels of thyroid stimulating hormone are often an indication of selenium and/or iodine deficiency.

Implications of Selenium Deficiency

Selenium deficiency may contribute to the development of a form of heart disease, hypothyroidism, and a weakened immune system. There is evidence that selenium deficiency does not usually cause illness by itself. Rather, it can make the body more susceptible to illnesses caused by other nutritional, biochemical, or infectious processes. Additionally, selenium deficiency may worsen the effects of iodine deficiency.

Three specific diseases have been associated with selenium deficiency: Keshan Disease, which results in an enlarged heart and poor heart function in selenium-deficient children; Kashin-Beck Disease, which results in osteoarthritis in children; and Myxedematous Endemic Cretinism, which results in mental retardation in infants born to mothers deficient in both selenium and iodine.

Treatment of Selenium Deficiency

The incidence of Keshan disease is closely associated with very low dietary intakes of selenium and poor selenium nutritional status. Selenium supplementation protects people from developing Keshan disease but cannot reverse heart muscle damage once it occurs. There is little evidence that improving selenium nutritional status prevents Kashin-Beck disease.

Food Sources of Selenium

At-Risk Regions

China, North Korea, and eastern Siberia.

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