Humans and animals are both capable of absorbing and utilizing both organic or inorganic forms of selenium from food or water sources. Most of the selenium that enters the body is excreted in the urine within 24 hours. Selenium can build up in the body if exposure is high and occurs over a long period of time. Body burdens of selenium primarily occur in the liver, kidneys, hair, and nails. Selenium is an essential dietary element for both human and animals in either the inorganic or organic form.
Selenium has antioxidant effects which help prevent damage to tissues caused by oxygen.
A selenium deficient diet can result in Keshan disease, the signs and symptoms of which may include muscle pain, cardiomyopathy, enlargement of the heart, increased red blood cell fragility, and pancreatic degeneration. No human populations in the U.S. have been reported to have chronic selenium toxicity, including populations in the western part of the country with naturally high levels of selenium in the soil and water. There have been a limited number of case reports of individuals who developed minimal signs of selenium toxicity following chronic dietary intakes of 850-900 ug per day. The MRL is an estimate of the daily human exposure to a hazardous substance that is likely to be without appreciable risk of noncancer health effects over a specified duration of exposure. The MRL was derived from a study involving a Chinese population with high selenium intake.