At first, newborns who are given formula may not be able to digest all of the milk sugar (lactose) in the formula they drink. The undigested lactose moves to the large intestine and causes cramps, bloating, or gas. As the baby grows, he or she is better able to digest the lactose, and the symptoms disappear.
Milk sugar intolerance is similar to lactose intolerance in older children and adults. But it is temporary and does not mean that the baby will be lactose-intolerant as an adult.