Tips On Relieving Constipation

At my son’s one year appointment yesterday I asked about switching him to whole milk instead of formula. He said that formula has more nutrients and the next step formula is very good for him, but that it isn’t necessary. So I said, how much milk/formula should he have a day? and he said that he doesn’t even have to have milk at all, it’s just good because of the fat content, and that he should be getting most of his nutrients from solid foods by now. I thought milk was important in a child’s diet? I also thought formula was no longer important at all? He also said that if we give him milk and he has a reaction to it-like constipation-then we should put off giving him milk for another YEAR. I can’t imagine not giving him milk or formula until he is two….and I certainly can’t afford to buy formula for another year, it’s been hard enough his first year.
Did anyone else’s doctor say these things? What would you do? What did your dr. tell you?

if your child were 4 or 5 months old, would you give them prune juice or something of the like to help with constipation?

and also, what kinds of foods, should a child about 13 yrs old, be eating, like how much veggies how much this how much that…1 more thing, do eating a lot of peanuts help constipation???