I have AS and Crohn's disease. A clean Mediterranean diet and probiotics saved me. The first thing I did was cut out all processed (fast) foods then I went on to eliminate other foods that caused me to flare- beef, pork and artificial sweeteners.
It took a long time but was well worth it. I suggest taking it step by step and talking with your doctor. Every patient is going to be different.

Eliminate breads, sugars, replace with vegetables low sugar fruits. If you do Pinterest there are oodles of recipes...