Therefore, protein intake moderately above requirement is supposed to be safe. However, studies in recent years have shown that high protein, especially high animal protein intake, may have an adverse effect on human health. Zhao et al. Along with the changes of dietary pattern, the disease pattern has also changed. For example, the leading causes of mortality for the Shanghai population in 1985 were malignant tumours, cerebrovascular diseases and ischemic heart disease, while in the 1950s, measles, tuberculosis and other communicable diseases were the leading causes of death.
Animal foods are rich in saturated fat and also in animal protein.
It is usually difficult to separate their independent effects. It is also well known that a high protein diet can increase the calcium excretion and cause calcium loss from the bone. When the basal diet was supplemented with methionine and cystine the same effect on Ca and sulphate excretion was observed 8 . Abelow et al. Dietary protein, sulphur amino acids and urinary Ca excretion .