Selenium is a trace mineral found in soil, water and some foods. The selenium content of food varies depending on the selenium content of the soil where the animal was raised or the plant was grown. Selenium is an essential element in several metabolic pathways and functions largely through its association with proteins, known as selenoproteins. Known biological functions of selenium include defense against oxidative stress and regulation of thyroid hormone action. Absorption of selenium is efficient with more than 90 percent of selenomethionine, the major dietary form of the element, being absorbed through the intestine 1.
The U.S. Food and Drug Administration (FDA) has established a Reference Daily Intake (RDI) of 70 μg selenium for adults and children 4 or more years of age (21CFR101.9). RDIs are a set of dietary references for essential vitamins and minerals that are considered amounts sufficient to meet the daily requirements of healthy individuals. RDIs serve as the basis for calculating the percent daily value (%DV) amounts found on dietary supplement and food labels.