It is better for children to drink plain milk for a long time because children are growing and their bones will need more calcium to grow. If children are not given enough calcium, they may suffer from calcium deficiency, such as excessive sweating and growing pains, as well as chicken breasts. When children are given plain milk, it is an effective source of calcium and is the best food source for calcium because of its high absorption rate. However, when drinking pure milk, it is better for children over three weeks of age, because the intestinal development of children within three weeks of age is not perfect, and children need to drink infant formula-based. If you drink pure milk too early will cause maladjustment, there will be abdominal pain, diarrhea, etc..