Teaching a child what to eat begins from the moment they are born and begin to nurse at their mother’s breast. A mother who understands will have prepared herself physically to be as healthy as possible to be able to provide her child with milk that is good for them. It is a cycle that goes from mother to child to mother to child again and again and again.
And the father is also a contributor: what he takes into his body affects the baby as well, as studies have shown that males who drink alcohol, smoke, or do drugs negatively impact the future health of their offspring as well!
There is much to learn about what is good to eat and how much to eat, but like everything else in nurturing children, the basics are small and simple: eat whole foods as close to their natural state as possible and in moderation. Drink plenty of water.