Phenylketonuria does not require a lifetime of special milk consumption. It is the first genetically inherited metabolic disorder that can be treated through dietary control. Once diagnosed with phenylketonuria, one must stop a natural diet and begin treatment with a low-phenylalanine diet. The low-phenylalanine milk formula should be consumed at least until the age of 12. When the concentration of phenylalanine in the blood is controlled within the ideal range, it is possible to appropriately add a small amount of natural diet, adhering to principles of low protein and low phenylalanine.