Visit the Microscopic Colitis Foundation Website
Someone here may have caught up with this already, but it's new to me:
http://www.nytimes.com/2011/04/21/scien ... ref=health
They've found that among the people they've studied, there are basically 3 'types' of gut ecosystems. Different families of bacteria predominate in each of the three, and the types produce different amounts of enzymes for producing various B-vitamins.
I haven't read the Nature article referred to in the NYTimes link. It sounds like a very new area, with huge implications no one can entirely predict. But it might explain why some gluten-sensitive people have more or less severe symptoms, or why some antibiotics create disastrous gut results - but not for everyone, or why some people find probiotics useful, and/or which ones would be more likelier to help.
(By "might explain," I mean I just made up some stuff speculatively.)
--Sara
NYTimes article re: 'Enterotype' in humans
Moderators: Rosie, Stanz, Jean, CAMary, moremuscle, JFR, Dee, xet, Peggy, Matthew, Gabes-Apg, grannyh, Gloria, Mars, starfire, Polly, Joefnh
They're on the right track, but I believe they're trying to being too simplistic when they attempt to categorize the distinction into only three classes. Actually, there are distinct differences between the gut population demographics of virtually every group of individuals who subsist on foods that differ significantly from the diet of other groups. For example Eskimos will have a unique gut bacteria arrangement, and the gut bacteria of vegans will drastically differ from the gut bacteria of people who eat mostly meat, and few other selections. 
Tex
Tex
It is suspected that some of the hardest material known to science can be found in the skulls of GI specialists who insist that diet has nothing to do with the treatment of microscopic colitis.