i am not sure but as we get older we lose the ability to keep producing enzymes to digest our foods properly like when we were younger ,,,,, u are still young if u are drinking 2 pints of milk a day without diarrhea and without getting gas pains maybe it has to do with the cereals ,,, u could for a week or so give them both a break and see if this improves ,,,,or try a different cereals like oats....