The CCFA funded medical journal Inflammatory Bowel Diseases recently published an article titled "Mechanisms of action of probiotics: Recent advances."
As described in the text below, manipulating the intestinal flora is "likely to become" a key component in treating Crohn's disease and ulcerative colitis:
Understanding probiotic action may permit modulation of the immune system, both locally and systemically. Knowledge of probiotics on the host immune system has entered a new and fascinating phase of research and progression in this field is likely to offer novel and useful means to modulate host immunity for protection from, or treatment of, a wide variety of human disorders, including IBD.
The specific carbohydrate diet is designed to exert probiotic effects on the intestinal flora--in combination with traditional IBD medication. Until the perfect probiotic product is available, you can pick up a used copy of Breaking the Vicious Cycle through amazon for about $15 and have the future here now:)