When can selenium deficiency occur?
Selenium deficiency is most commonly seen in parts of China where the selenium content in the soil, and therefore selenium intake, is very low. Selenium deficiency is linked to Keshan Disease. The most common signs of selenium deficiency seen in Keshan Disease are an enlarged heart and poor heart function. Keshan disease has been observed in low-selenium areas of China, where dietary intake is less than 19 mcg per day for men and less than 13 mcg per day for women. This intake is significantly lower than the current RDA for selenium.
Selenium deficiency also may affect thyroid function because selenium is essential for the synthesis of active thyroid hormone. Researchers also believe 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 neurologic effects of iodine deficiency.
Selenium deficiency has 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 physicians can recommend appropriate treatment.
Who may need extra selenium?
Selenium supplementation is essential for anyone relying on TPN as the sole source of nutrition, and selenium supplementation has become routine during TPN administration since the relationship between selenium deficiency and TPN was discovered. Gastrointestinal disorders such as Crohn's disease can impair selenium absorption. Most cases of selenium depletion or deficiency are associated with severe gastrointestinal problems, such as in individuals who have had over half of their small intestines surgically removed. A physician, who will determine the need for selenium supplementation, should evaluate individuals who have gastrointestinal disease and depleted blood levels of selenium.