SIgA is an antibody found in breastmilk (and lots of other bodily fluids) that helps infants set up healthy colonies of gut bacteria. Without it, baby mice develop symptoms of irritable bowel syndrome when exposed to environmental stressors. One question I have: While there are some studies that suggest formula fed babies are at a higher risk of IBD, the link between not getting SIgA from breastmilk and developing IBD doesn't seem to be an absolute "this will happen" in humans. Not by a long shot. Which leaves me wondering, "Why?"