It's been over 10 years now so I don't remember specifics, but it wasn't a specific trigger food (other than the usual gluten/high fiber/etc stuff to avoid), but some supplements (I remember Cat's Claw was one, as well as turmeric) and some non traditional produce in the American market (like celery root and mung beans)
After about 6 months of this regimen the nutritionist suggested the random pains she was getting from otherwise everyday foods was gone. Of course still the same predictable issues with certain foods, but no guess work anymore as to what causes issues.