Keshan disease is an endemic cardiomyopathy with unknown causes  The two epidemics of Keshan disease in Shandong Province occurred in the period of difficult life of residents in the disease area  At this time, the residents had a single diet structure and lack of nutrition  After 1978, due to the reform of rural economic system, the life of residents in the disease area gradually improved, the nutritional structure tended to be reasonable, and there were fewer and fewer new patients of Keshan disease, meeting basic control standards
Before 1978, the living standard in rural areas was generally low, but Keshan disease only appeared in some places (the relationship between nutritional deficiency and Keshan disease was partially recognized, which can not be questioned), and the inference was partially recognized, which can not be questioned
Some researchers speculate that nutritional deficiency may be an important factor in the pathogenesis of Keshan disease