I'd DEFINITELY do a two week trial. No whole wheat pasta, breads, etc. Brown rice may or may not be ok but may best to avoid it for two weeks too and then add that back in before the whole meal flour items? And eventually you may be able to slowly transition him to whole wheat, etc by slowly adding it in (like 3/4 white, 1/4 whole wheat, etc) but I'd definitely hold off for now.