What is Selenium?
Selenium is an essential trace element the body needs for good health and proper functioning. It is found in soil and water and is bioconcentrated by plants from the soil. Plants and animals that live in places where the soil is rich in selenium have high amounts of this mineral.
Selenium exists in inorganic and organic forms. Inorganic selenium occurs in the soil as selenite and selenate while organic selenium occurs as selenoproteins such as selenocysteine and selenomethionine. Plants accumulate inorganic selenium from the soil and converts this to organic form, which is consumed by animals and man.
In the body, selenium is incorporated with aminoacids like methionine to form selenomethionine. It is mostly stored as proteins in the skeletal muscles, which account for up to 46% of the total selenium found in the body. Other forms of organic selenium may be converted to selenophosphate for the synthesis of other selenoproteins.
Selenium is essential as a cofactor of certain enzymes that help maintain normal body functions. For example, it aids in the reduction of glutathione peroxidase enzymes, which have antioxidant activity. It also acts as a cofactor of thyroid hormone enzymes and is therefore important in all thyroid gland activities.
Selenium Food Sources
Selenium rich foods include seafoods, organ meats, muscle meats, dairy products, cereals and grains, breads, poultry, and eggs. Nuts, especially Brazil nuts and walnuts, are excellent selenium foods. Eating just 6-8 pieces of Brazil nuts can supply more than 700% of the daily value (DV) of selenium recommended by the U.S. Food and Drug Administration (FDA). Many types of fish, like cod, tuna, halibut, sardines, herring, and red snapper are good selenium sources.
The amount of selenium in food depends largely on the amount of the mineral found in the soil as well as other factors, including the amount of organic matter, soil pH, and the form of selenium that is plants can use. Therefore, the concentration of selenium in plant foods vary widely depending on the location, as well as the amount of mineral found in animals eating the plants. However, animals can maintain predictable concentrations of selenium in their tissues. It has been observed that slenium concentrations are higher in people living in the Western and Midwestern parts of the United States than in residents of the Northeast and Southern parts. However, because foods can be transported to different places, people living in areas with low-selenium may still obtain enough of this mineral from foods.
Benefits of Selenium
Selenium plays an important role in many body functions and is known to possess antioxidant activity. Some studies show that it may have important health benefits, particularly in the prevention of cancer, thyroid disease, cardiovascular disease, and mental decline.
Its important effects on the immune system, cancer death and DNA repair, as well as its antioxidant activities suggest that it...