Everyone is different, you'll find!
Mine are iceberg lettuce, some tomato sauces (Pizza Hut, ugh), hard liquor, fresh spinach & big salads
And, apparently, gluten.
49 year old female attorney, diagnosed UC/pancolitis 1985, no surgery but much suffering.
Asacol/5ASA 6x400 mg maintenance for 20+ years; use prednisone & Rowasa for flares.
August 2008 sought care of naturopathic doctor. Food sensitivity test showed gluten, other intolerances; started diet without gluten, soy, dairy, tomato etc. Replete probiotic first, then Forte pills.
Achieved remission for the first time in many, many years!? Seemed so, but colonoscopy Oct. 6 proved not so, heavy inflammation in ascending colon & will be using Rowasa again. But I AM better.