Although what I did was considered controversial and unorthodox at the time (not so much these days) I went onto a full juice fast firstly (3 days) and then rebuilt my digestive health 1 element at a time. Started out with chicken breast, then a green veggie, followed by another animal protein and then another veggie...finally added the fruits but stayed totally away from carbs and dairy...that lasted for quite a while until my whole system balanced out. While doing that my GP put me on the very first perscription grade (customed it from the pharma-lab and it was fed-xed using refridgeration...potent stuff) probiotic.
It was a 30 day run and seemed to do the trick.
I have been pretty lucky since then and I am not sure if it is my pouch maturing or the whole dissociated diet that kept me stable but I honestly did not break the diet from 1992-2006...so it was probably a bit of both.
I also live in Europe and most of the food that I ate was 100% natural and non-refined nor prepared. Haven't eaten a delivery pizza in over 20yrs.
Nowadays they call it Paleo or some such but honestly it is just common sense to eat as simply and naturally as possible, avoid refined foods, junk, additives and chemicals if at all possible.
All that said, sometimes, no matter what you do, it just does not help. When I had a systemic infection (necrosis behind the pouch) I tried everything including sea-water irrigation of the pouch and antibiotic rinces but they just didn't help.
My motto is do your best and hope that it works.