Selenium is one of the essential trace elements and is a strong antioxidant with similar effects to vitamin E but with greater potency. Selenium can be used to regulate the rate of redox reactions in the body, affect the metabolism and activity of certain important enzymes, and regulate the absorption and consumption of vitamins A, C, E and K in the body. Selenium is also an important component of glutathione peroxidase in the body, which has a protective effect on the structure of cell membranes and promotes the immunity of the body. Selenium deficiency is an important cause of Keshan disease. Selenium deficiency induces liver necrosis and selenium deficiency induces cardiovascular disease. In people with mild or moderate selenium deficiency, signs and symptoms are not obvious. What are the causes of selenium deficiency? Selenium is an important trace element to maintain normal physiological function of human body. Selenium is absorbed by the intestine after being ingested by the body and distributed in organs such as liver, spleen, kidney and heart. Selenium is combined with proteins and transported to tissues via blood, and selenium is involved in constituting glutathione peroxidase, which can catalyze the conversion of reduced glutathione into oxidized glutathione and prevent the damage of hydrogen peroxide and oxidized lipids to cells. Selenium deficiency is an important cause of Keshan disease. Selenium deficiency induces liver necrosis and selenium deficiency induces cardiovascular disease. In people with mild or moderate selenium deficiency, signs and symptoms are not obvious. Selenium deficiency causes Keshan disease and big bone disease In 1935, a strange disease was discovered in Keshan County, Heilongjiang. This kind of patient had pale face, cold hands and feet, dizziness, shortness of breath, nausea, vomiting and high mortality. At that time, no cause could be found, and there was no prevention and treatment method, so the disease was named “Keshan disease”. Later in the northeast, north China, southwest and many other places have found this disease. A lot of information shows that low selenium status plays an important role in triggering Keshan disease, and the selenium content of the patient’s heart muscle is significantly lower than that of normal people. Selenium supplementation to prevent Keshan disease has achieved significant results. In the 1970s, we started to use sodium selenite to prevent and control Keshan disease with some effect, and found that the natural environment of the disease area and the human body are deficient in selenium, and later tried selenium prevention in 69 counties in more than ten provinces and regions, and 1.42 million people took selenium preparations, which achieved significant preventive effect. By taking selenium preparations orally to the residents of the disease area for prevention, its effect is remarkable and the incidence rate is significantly reduced. ”Large osteoarthrosis” is also an endemic bone deformation disease of unknown cause, patients mainly manifest as cartilage disorders and joint deformities, pathological changes to both ends of the tubular bone tissue damage and multiple cartilage necrosis, the onset of the region often overlap with Keshan disease, so there is Keshan disease “sister disease ” is called. When Keshan disease was found to be related to selenium deficiency, the relationship between macroosteosis and selenium also began to be considered, and the prevention of the disease with sodium selenite was started, and when a certain effect was found, children were given sodium selenite for 6 years in a seriously ill area, and selenium preparations were found to have ideal preventive and therapeutic effects. At present, the prevention of selenium supplementation for macrosomia has been consistently practiced on a large scale.