What is selenium?
Selenium is a trace mineral that is essential to good health but required only in small amounts. Selenium is incorporated into proteins to make selenoproteins, which are important antioxidant enzymes. The antioxidant properties of selenoproteins help prevent cellular damage from free radicals. Free radicals are natural by-products of oxygen metabolism that may contribute to 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.
What foods provide selenium?
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 plants are grown or animals are raised.
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 muscle. In the United States, meats and bread are common sources of dietary selenium. Some nuts are also sources of selenium.
Selenium content of foods can vary. For example, the U.S. Department of Agriculture Food Composition Database lists the selenium content of Brazil nuts as 544 mcg of selenium per ounce, but values from other analyses vary widely. It is wise to eat Brazil nuts only occasionally because of their very high selenium content.
When can selenium deficiency occur?
Human selenium deficiency is rare in the United States but is seen in other countries, most notably China, where soil concentration of selenium is low. There is evidence that selenium deficiency may contribute to development of a form of heart disease, hypothyroidism, and a weakened immune system. There is also 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 stresses.
Three specific diseases have been associated with selenium deficiency:
1. Keshan disease, which results in an enlarged heart and poor heart function, occurs in selenium deficient children.
2. Kashin-Beck disease, which results in osteoarthropathy.
3. Myxedematous endemic cretinism, which results in mental retardation.
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Keshan disease was first described in the early 1930s in China, and is still seen in large areas of the Chinese countryside with selenium poor soil. Dietary intake in these areas is less than 19 micrograms per day for men and less than 13 micrograms per day for women, significantly lower than the current RDA for selenium. Researchers believe that selenium deficient people infected with a specific virus are most likely to develop Keshan disease.
Selenium deficiency has also been seen in people who rely on total parenteral nutrition (TPN) as their sole source of nutrition. TPN is a method of feeding nutrients through an intravenous (IV) line to people whose digestive systems do not function. Forms of nutrients that do not require digestion are dissolved in liquid and infused through the IV line. It is important for TPN solutions to provide selenium in order to prevent a deficiency. Physicians can monitor the selenium status of individuals receiving TPN to make sure they are receiving adequate amounts.
Severe gastrointestinal disorders may decrease the absorption of selenium, resulting in selenium depletion or deficiency. Gastrointestinal problems that impair selenium absorption usually affect absorption of other nutrients as well, and require routine monitoring of nutritional status so that appropriate medical and nutritional treatment can be provided.
Who may need supplemental selenium?
In the United States, most cases of selenium depletion or deficiency are associated with severe gastrointestinal problems, such as Crohn's disease, or with surgical removal of part of the stomach. These and other gastrointestinal disorders can impair selenium absorption. People with acute severe illness who develop inflammation and widespread infection often have decreased levels of selenium in their blood. Physicians will evaluate individuals who have gastrointestinal disease or severe infection for depleted blood levels of selenium to determine the need for supplementation.
People with iodine deficiency may also benefit from selenium supplementation. Iodine deficiency is rare in the United States, but is still common in developing countries where access to iodine is limited. Researchers believe that selenium deficiency may worsen the effects of iodine deficiency on thyroid function, and that adequate selenium nutritional status may help protect against some of the neurological effects of iodine deficiency.
As noted above, selenium supplementation during TPN administration is now routine. While specific medical problems such as those described above indicate a need for selenium supplementation, evidence is lacking for recommending selenium supplements for healthy children and adults.
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The Dietary Guidelines for Americans describes a healthy diet as one that:
Emphasizes a variety of fruits, vegetables, whole grains, and fat-free or low-fat milk and milk products.
Whole grain breads, cereals, and noodles, brown rice, and low fat cottage cheese can be good sources of selenium.
Includes lean meats, poultry, fish, beans, eggs, and nuts.
Lean beef, fish, eggs, and poultry can be excellent sources of selenium. Brazil nuts contain high amounts of selenium.
Is low in saturated fats, trans fats, cholesterol, salt (sodium), and added sugars.
Stays within your daily calorie needs.
What foods provide selenium?
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 plants are grown or animals are raised.
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 muscle. In the United States, meats and bread are common sources of dietary selenium. Some nuts are also sources of selenium.
Selenium content of foods can vary. For example, the U.S. Department of Agriculture Food Composition Database lists the selenium content of Brazil nuts as 544 mcg of selenium per ounce, but values from other analyses vary widely. It is wise to eat Brazil nuts only occasionally because of their very high selenium content.
When can selenium deficiency occur?
Human selenium deficiency is rare in the United States but is seen in other countries, most notably China, where soil concentration of selenium is low. There is evidence that selenium deficiency may contribute to development of a form of heart disease, hypothyroidism, and a weakened immune system. There is also 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 stresses.
Three specific diseases have been associated with selenium deficiency:
1. Keshan disease, which results in an enlarged heart and poor heart function, occurs in selenium deficient children.
2. Kashin-Beck disease, which results in osteoarthropathy.
3. Myxedematous endemic cretinism, which results in mental retardation.
.jpg)
Keshan disease was first described in the early 1930s in China, and is still seen in large areas of the Chinese countryside with selenium poor soil. Dietary intake in these areas is less than 19 micrograms per day for men and less than 13 micrograms per day for women, significantly lower than the current RDA for selenium. Researchers believe that selenium deficient people infected with a specific virus are most likely to develop Keshan disease.
Selenium deficiency has also been seen in people who rely on total parenteral nutrition (TPN) as their sole source of nutrition. TPN is a method of feeding nutrients through an intravenous (IV) line to people whose digestive systems do not function. Forms of nutrients that do not require digestion are dissolved in liquid and infused through the IV line. It is important for TPN solutions to provide selenium in order to prevent a deficiency. Physicians can monitor the selenium status of individuals receiving TPN to make sure they are receiving adequate amounts.
Severe gastrointestinal disorders may decrease the absorption of selenium, resulting in selenium depletion or deficiency. Gastrointestinal problems that impair selenium absorption usually affect absorption of other nutrients as well, and require routine monitoring of nutritional status so that appropriate medical and nutritional treatment can be provided.
Who may need supplemental selenium?
In the United States, most cases of selenium depletion or deficiency are associated with severe gastrointestinal problems, such as Crohn's disease, or with surgical removal of part of the stomach. These and other gastrointestinal disorders can impair selenium absorption. People with acute severe illness who develop inflammation and widespread infection often have decreased levels of selenium in their blood. Physicians will evaluate individuals who have gastrointestinal disease or severe infection for depleted blood levels of selenium to determine the need for supplementation.
People with iodine deficiency may also benefit from selenium supplementation. Iodine deficiency is rare in the United States, but is still common in developing countries where access to iodine is limited. Researchers believe that selenium deficiency may worsen the effects of iodine deficiency on thyroid function, and that adequate selenium nutritional status may help protect against some of the neurological effects of iodine deficiency.
As noted above, selenium supplementation during TPN administration is now routine. While specific medical problems such as those described above indicate a need for selenium supplementation, evidence is lacking for recommending selenium supplements for healthy children and adults.
.jpg)
The Dietary Guidelines for Americans describes a healthy diet as one that:
Emphasizes a variety of fruits, vegetables, whole grains, and fat-free or low-fat milk and milk products.
Whole grain breads, cereals, and noodles, brown rice, and low fat cottage cheese can be good sources of selenium.
Includes lean meats, poultry, fish, beans, eggs, and nuts.
Lean beef, fish, eggs, and poultry can be excellent sources of selenium. Brazil nuts contain high amounts of selenium.
Is low in saturated fats, trans fats, cholesterol, salt (sodium), and added sugars.
Stays within your daily calorie needs.
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