Babies 5 - 11 months old are very rampant for them to constipate. I totally agree the best laxative is milk. Fresh and properly washed fruits to blend is the next best remedy to give to the young ones with this constipation issue.
From my experience, as a mom of 3 adults children & with 9 mos old granddaughter here are the best remedies for constipation: fresh squeezed sweet orange juice, papaya juice,(from the oriental store), prune juice, and give them soft solids easy to digest foods. They don't have complete teeth yet and their digestive organ still very small. Don't feed too much or not also less just enough for their tummy. Sometimes we are overwhelmed feeding our babies too much we forget that the outcome is no good.