I am in the process of finding this out! I was recently diagnosed with microscopic colitis, and went on a very restricted diet to heal my innards, while waiting for my testing for food sensitivities to be completed. After 2.5 weeks I feel better than I have in YEARS - the pain (body pain AND intestinal difficulties) is very much reduced and my energy level has increased and I'm sleeping better - without pain, too. So right now I am eating proteins (meats, seafood, eggs, no beans) and a few very well cooked and peeled fruits and veggies. No grains, no legumes (inc soy), no sugar, no dairy. I'm adding in a new veg every few days (peeled and cooked), and so far only bell peppers caused me some joint pain. Nightshades are implicated in autoimmune stuff, so I ruled them all out for a few more weeks.
So right now I'm waiting on results for Enterolab testing and a biopsy for celiac disease (MC is strongly correlated with celiac). And then I'll know what to REALLY avoid, but there might also be foods that make my symptoms worse for other reasons (fiber, immune stuff), and I'll get a better idea of those over time.
I was really interested to learn that MC is strongly related to Sjogren's syndrome and Fibro, both of which I have. Common cause or some causing the others? Likely! Happy to have some info after so many years.
Feeling really good about this, especially after 2 pain free weeks.