Tell the truth, but don't talk too much about
it. You don't want it to become the center of the conversation on the first date.
For instance, you could say that you're having some digestive issues today/tonight and leave it at that. Later, after you've been dating for awhile, you could explain that you have UC. She will understand.
Saying that you have stomach issues isn't quite right, especially if you later tell her that you have colon issues. I would get confused and think: Is it stomach issues or colon issues? Did you lie? Can you be trusted to tell the truth?
Colitis is in remission. No longer get IBS.
Figuring out how to reduce a flare or get into remission is a trial and error experience. Don't expect your GI to have all the answers. He was trained in making diagnoses, prescribing medications, and surgically removing the colon. He was not trained in alternative treatments. That's why they are called alternative treatments.
What works for me: Fecal transplantation, Probiotics, Anti-inflammatory foods, No HFCS, No crystalline fructose, No foods high in fructose, No artificial sweeteners, No pro-inflammatory foods when flaring, vitamins & supplements, Lexapro (for stress).