What is known about the mechanisms of dietary influences in Crohn's disease?

Much has been written about the role of diet and risk for Crohn's disease (CD). However, the evidence is contradictory. Recent evidence has pointed to fiber playing an important role along with the possibility that dietary fat and overnutrition also have a role. Diet has a clearer place in disease modification, with some diets used in the treatment of CD. The lack of clarity stems from a poor understanding of the mechanisms underlying the relationship between diet and CD. Gut permeability is likely to play a key role in the risk for CD. Mechanisms whereby diet can affect gut permeability, including the effects of the gut microbiota, are reviewed. Modification of disease behavior is likely to be influenced by additional mechanisms, including recognition of complex food antigens. As with many other chronic diseases, a surrogate marker of CD risk would greatly aid evaluation of the dietary factors involved. Formal measures of gut permeability are too cumbersome for large-scale use, but fecal calprotectin may be a convenient measure of this. There are only preliminary data on the effect of diet and microbiota composition on fecal calprotectin and these require further investigation.