Some fibers ferment and cause gas. Even the "no gas" varieties (e.g., Citrucel smart fiber) gave me gas when my colon was very hot. Now with some relief from 5-asa oral and rectal, I have been tolerating the fiber. Borderline constipation is still an issue though.
I also have poor absorption of bile salts due to missing part of my terminal small intestine. This left me with diarrhea even after the 5-asa had cleared most of my colon. The drug Colesevelam binds the salts, but really increases the constipation. I am trying to find dosing schedules of rectal meds and maybe every other night Colesevelam and 3x daily fiber tablets and plenty of fluids that will let me find the good spot between diarrhea and constipation.
The constipation is not pleasant, but I can at least work, where this was problematic with chronic diarrhea.