there is a link between wheat and crohn's,
In all people wheat will upregulate the production of zonulin which will increase intestinal permeability[1], allowing molecules from the intestine into the bloodstream which would normally not be absorbed.
All the analysis of this study is way over my head, but Chris Masterjohn (The Daily Lipid) suggests that there is more in play than just gliadin (a glycoprotien in wheat), such as bacteria and yeast imbalances affecting the impact of gliadin on zonulin production.
Then your specific genetics will determine how your body reacts to these toxins, -MS, Hashimo's, Celiac, arthritis, Crohn's, Diabetes, you name it.[2]
Whatever the whole story, there is a lot to suggest that if you don't have leaky gut then you won't have crohn's (or almost any other immune disorder )
I'd recommend going fully paleo and then adding back a few things like hard cheeses and white rice if they are tolerated
further reading....
http://www.fourhourworkweek.com/blog/2010/09/19/paleo-diet-solution/
http://perfecthealthdiet.com/category/disease/autoimmune/
http://perfecthealthdiet.com/2010/10/wheat-is-a-cause-of-many-diseases-i-leaky-gut/ (includes a specific mention of crohn's and wheat)
[1]
http://www.ncbi.nlm.nih.gov/pubmed/16635908
“Based on our results, we concluded that gliadin activates zonulin signaling irrespective of the genetic expression of autoimmunity, leading to increased intestinal permeability to macromolecules.” the degree of increase varied amongst test patients,
[2]http://www.ncbi.nlm.nih.gov/pubmed/19538307
”Therefore, we hypothesize that besides genetic and environmental factors, loss of intestinal barrier function is necessary to develop autoimmunity. In this review, each of these components will be briefly reviewed.”