Let's not forget about
the "old friends" (bacteria, parasites, and who knows maybe even certain viruses) and hygiene hypotheses. While they probably are not a complete answer to the puzzle- it's patently obvious how diverse our responses are to different therapies, diets, etc- and are not yet iffering anything like a magic bullet, the science behind them does show that lack of exposure in infancy and childhood to old friends results in one having a stunted, untrained, incompletely regulated immune system for the remainder of ones life.
The reason that worm therapies, to name one therapy based on the "old friends" hypothesis, may not work on everyone (I tried three- TSO= pig whipworm eggs, human hookworms, and human
whipworms, and only the TSO turned out in my case to have some modest but definite damlening effect on my UC) is because the horse is out if the barn- our immune systems were largely formed in infancy. Granted, that doesnt explain how people from countries where they we exposed to old friends, migrate to the West, lose the old friends and get IBD - though one can speculate that they might respond better to such therapies. In any case, while for the forseeable future I am not looking into worm therapies again any time soon, I think that intestinal parasites must be viewed in the same frame if mind as intestinal bacteria.
Another thought, in light of the Attachment Parenting trend (and controversy)- Attachment parenting includes an emphasis on breast feeding, when practical, up to a few years of age. This was common in traditional hunter gatherer (i e paleo) societies - many even shared nursing of infants, further diversifying probiotic diversity- and would surely have primed a child's immune system massively compared to what is common in the West today.
"In order to save the
organ, we had to
remove it" --