Mineral deficiencies have caused severe health consequences in developing countries. Among many other minerals, selenium is also an essential nutritional trace mineral element that is critical to the normal physiology of humans. In 1817, Swedish chemist and physician Jons Jacob Berzelius discovered this element. The US Department of Agriculture has an RDA of 55 μg/day for adults. Regional dietary deficiency of selenium caused Keshan and Kashin-Beck diseases. Keshan disease is endemic congestive cardiomyopathy, characterized by cardiac insufficiency, heart enlargement, arrhythmia, and electrocardiographic modifications. First identified in 1935 in Keshan County, Heilongjiang Province, northeast China. This disease is clinically divided into four categories: acute, subacute, chronic, and latent. However, selenium supplementations to the residents of Keshan disease endemic areas significantly reduced the incidence of KD. Thus, the government decided to apply sodium selenite to growing crops, and the incidence of the disease decreased dramatically.