system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why can't babies drink water until they are six months old?

I have read that babies shouldn't drink water until they are six months old. So what changes in babies from infancy and six months later?
gpt
Newborns receive all their nutrition from breast milk or formula. They also have very small stomachs, and if you fill the stomach with water, they won't be hungry for milk or formula and thus might not receive adequate nutrition. As they grow, their stomachs become larger and their digestive system better equipped to handle mushy foods and water in addition to breast milk or formula.