The infant’s stomach is more mature by about 1 year of age because the stomach of a small infant is horizontal and has a more limited capacity, and esophageal and gastric reflux can easily cause overflow or spitting up of milk. At 4 months of age, the stomach matures as the infant grows older. The infant’s stomach can develop more perfectly around the age of 1 year, and its intake of food can transition from fluid to semi-fluid, semi-solid and solid, and stomach acid secretion is close to normal, so the digestive power will improve. After 4 months of life, the baby’s stomach and intestines will slowly develop, and the digestive ability and ability to absorb nutrients will be strengthened, so supplementary foods should be added slowly, from less to more to give the baby the process of adaptation, which is beneficial to the absorption of nutrients. When breast milk is not enough, formula can be used to ensure the normal absorption of nutrients.