Levels of Se in plant, animal and human food reflect the considerable variations that occur in soil Se throughout the world. In 12 out of 21 countries selenium intake in humans has been found to be below WHO recommended levels (40 male, 30 female ug/h/d). In humans low selenium (Se) intake has been linked to a higher risk of CVD, arthritis, infertility, immunosuppresion, adverse mood states and cancer. As a consequence, the concept of healthy food additives, with the term “functional foods” has been defined as a food that provides benefits beyond the traditional nutrients it contains. In this case selenium. The purpose of this work was to compare the effect of the source and level of selenium supplementation in the diets of lactating dairy cows on the selenium content of milk and cheese.