Professor of Medicine and Epidemiology University of Pennsylvania University of Pennsylvania Philadelphia, Pennsylvania
The prevalence of immune mediated diseases are increasing in the United States and world-wide. Inflammatory bowel disease (IBD), including both Crohn’s disease (CD) and ulcerative colitis (UC), are complex gastrointestinal disorders that arise in a genetically susceptible host due to factors involving immune cell dysregulation with an overly robust response to contents of the gut lumen. Whether the principle antigen that is driving the persistent inflammation is the gut microbiota, food, or some interaction of both of these is still being determined. However, because it is easier to modify diet than the gut microbiota, there has been renewed interest in dietary modification as a preventative, primary, or adjunctive therapy. A Western diet, high in refined carbohydrates, omega-6 fatty acids, and saturated fat, and low in fiber, vitamins, and generally nutrient dense foods, is associated with an increased risk of IBD. Dietary modification has been examined for both active IBD and maintenance of remission. Approaches to dietary intervention include exclusion of certain foods or food groups, with or without modification (such as parenteral or enteral nutrition), and supplementation. Clinical trials from many decades ago suggest comparable efficacy of bowel rest (food exclusion) with parenteral nutrition and enteral nutrition formulas for refractory Crohn’s disease and as such parenteral nutrition is rarely used. Similarly, there is little evidence to support the use of total parenteral nutrition for ulcerative colitis. The effectiveness of exclusive enteral nutrition for Crohn’s disease does not vary based on the nitrogen source (i.e. completely hydrolyzed, partially hydrolyzed, or intact protein) or by fat content. Compared to corticosteroids, exclusive enteral nutrition is more effective at reducing inflammation based on endoscopy or histology. Various defined diets have been tried by patients to manage symptoms and ideally help reduce inflammation. More than half of patients have experimented with a gluten free diet but far fewer remain on this long term. The specific carbohydrate diet, autoimmune protocol diet, Crohn’s disease exclusion diet, and low FODMAP diet are popular diets for which there is some evidence of effectiveness. Such diets are more complex and can be difficult to follow. For most patients, a generally healthy diet is recommended. For those seeking to use diet as therapy, it is important to monitor inflammation, symptoms and nutritional status.