Protein is digested to amino acids which are then absorbed into the bloodstream. These amino acids are then absorbed by all cells that require them for growth or the repair of tissue and are built up again into human protein.
All amino acids not needed for growth and repair have to be destroyed. The liver removes the amino group and converts the rest into sugar and then glycogen or fat. The amino group has to be converted into urea which is then removed from the blood by the kidneys.
Both the amino group and urea form an acid solution. Potassium and calcium are needed to neutralise this acid and are lost to the body. Excess protein in the diet puts the liver under stress. The loss of calcium may be made up by removing calcium from the bones and loss of potassium makes it more difficult for the body to balance the acid and alkaline substances in solution. The kidney has to deal with the acid end product of excess protein in the diet and is put under stress.
One protein meal a day provides most of us with all the protein that we need.