My son age 14 loves non-fat milk & drinks 2-3 glasses/day. is that too much? what is the right amount to drink? how does this change as we age?

Milk: As long as it is non-fat or skim milk, that isn't a problem. He will get his calcium for strong bones and teeth. Just make sure he is eating a variety of healthy foods as well. The fat in whole milk is not particularly healthy after toddlerhood, because it is high in cholesterol and saturated fats, so we switch to skim milk at 2 years old.