Your guess about
what foods your doctor was referring to is most likely wrong. The typical recommendation is to follow a "low residue" diet during flares, meaning avoiding fresh vegetables and things that leave a lot of bulk for the colon to digest, because they can cause added pain and bloating on top of the flare.
Many if not most GI doctors will not make any other recommendations related to diet because they view the evidence as too limited to substantiate anything. This is not unreasonable. There are some studies which suggest the influence of diet on the course of UC (for example:
http://gut.bmj.com/content/53/10/1399.full
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC549081/
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1774231/
), however, it does not constitute either a large or particularly consistent body of work and there isn't a consensus on the mechanism by which these would affect UC. It may be prudent to avoid red meat, or heavily-sulfited foods, or alcohol, but there just isn't the level of evidence there that would give a doctor a reason to tell you to do that.
I am of the opinion that most of the diets and especially the "trigger foods" mentioned by many people in the forum are almost entirely superstition. There may be a basis to some of them (e.g. carrageenan has been shown in high doses to induce colitis in rats, whether this has any relationship to UC as we know it is debatable), but the evidence is scant and equivocal. And the criteria that most people use for putting a food on their "trigger" list is wildly unscientific.
Post Edited (fredflats) : 3/25/2012 1:32:44 PM (GMT-6)