How funny, I made a thread with a similar topic on RunnersWorld (and received responses that were much less helpful, and ruder, which is why I prefer this site... but that's another story).

http://community.runnersworld.com/topic/how-to-eat-fewer-vegetables

For me, part of the problem is that I do actually have a disease/thing (my uncle, who has run a marathon, has the same condition; so does my cousin).  But the good news is that means I have done a LOT of research into what helps with stomach discomfort while running!

For me: more starch less fiber.  I am a big vegetable person.  Yeah, not so much before a long run.  Potatoes are AWESOME the night before a run, btw.  So are very well-cooked vegetables that are lower in fiber.  Zucchini is my favorite.  Salads are not my friend.

Also: lower fat for breakfast pre-run or at least a more digestible fat, i.e. peanut butter not bacon.  (Foolproof pre-long-run meal for me is toast with PB on one side, an egg on the other).  I hear oatmeal sits well for some.

Avoid excess caffeine!  If you can run without coffee, do so.  If you DO have coffee, DO NOT have it on an empty stomach and go with one cup, not two, preferably with about 1 tablespoon of milk (helps with acid).  And watch out with coffee pre-race, as well, as it speeds things up.  Unfortunately it is also a proven performance enhancer.  Coffee + immodium anyone?  Er. Hm.  Not tested that one out myself.

Also: eating more regularly but less at each sitting helps me.  That way you keep your digestive tract on a regular schedule.  So I eat small meals, spread out, and I don't fast before my run--I do eat something, just leave at least an hour to digest it before running.