Welcome! I've had ulcerative proctitis for over ten years, hospitalized twice for it. I was advised to stick to a low residue diet while flaring and to stay away from caffeine. Last year was my worse flare and I was in the hospital ten days with it. The flare lasted seven months and I was on prednisone all that time. I now am in remission (since Nov 1st actually). Odd thing about this disease is that when in remission you would never think you suffer from UP. But I know it is always lurking around.
My GI doctor advised me to take a probiotic. They gave me Flora Q in the hospital, but that is quite expensive. My nutritionist suggested Powerdophilus by Country Life and I order online. I believe it was $17.88 (which included shipping) for a bottle of 200. I keep them refrigerated and take two a day with meals. I also take calcium with vitamin D because I developed osteoporosis, most likely from the steroid use over the years, and a one a day multivitamin with iron. I don't have to take the steroid enemas anymore or Canasa. I am on Colazal 750mgm, 6 capsules per day. My GI doctor prefers Colazal instead of Asacol for ulcerative proctitis, it treats the lower portion of the colon moreso than Asacol. I've also been on 6MP for at least five years.
I now can eat mostly anything while in remission and do drink my one cup of coffee with caffeine without any adverse effects. I stay away from greasy or spicy foods.
Good luck to you and I hope you are feeling better soon.