Human needs for selenium are supplied mainly by plant foods, but also, to some extent, by seafood and certain meats. While selenium serves some industrial use, its primary use is in the prevention of selenium deficiency in animals and people. In chickens, reduced egg production, less hatchability and degeneration of the pancreas also occur. Selenium is an essential element for normal health and functioning of farm animals, and its necessity has been documented for human nutrition in 1976, including a possible role in aging, anticarcinogenic properties and blood clotting. Crops will be low in selenium when grown in areas with low selenium contents in the soil.
People living mainly on crops from such areas are at risk for low selenium intake.
Research with selenium supplementation to malnourished children resulted in significant weight gains. Within the United States, low levels of selenium have been found in breast milk and in babies' blood serum selenium contents from mothers living in areas with low selenium crops and soils. Selenium contents of cow, goat or sheep milk are hard to estimate from food content tables or textbooks, in part because of variability, depending on feed and food contents. Selenium is readily excreted in milk, thus milk contents are good indicators of the nutritional selenium status. Selenium should be part of baby formula, food and feed supplementation.