Combinatorial effects of diet and genetics on inflammatory bowel disease pathogenesis

Inflammatory bowel disease (IBD) encompasses a group of disorders affecting the gastrointestinal tract characterized by acute and chronic inflammation. These are complex and multifactorial disorders that arise in part from a genetic predisposition. However, the increasing incidence of IBD in developing countries suggests that environmental factors, such as diet, are also critical components of disease susceptibility. Evidence suggests that consumption of a Western diet, enriched with saturated fat, refined carbohydrates, and food additives, is associated with increased IBD risk. Dietary components, such as omega-6 fatty acids, long-chain fatty acids, protein, and digestible carbohydrates, may contribute to IBD pathogenesis through altering intestinal microbiota, increasing intestinal permeability, and promoting inflammation; whereas omega-3 fatty acids, medium chain triglycerides, and nondigestible carbohydrates improve these parameters and intestinal health. However, the limited amount of prospective studies, small sample sizes, and the heterogeneity of disease subtype result in inconsistencies between studies and difficulty in conclusively determining the specific effects of diet on intestinal homeostasis. There are no standard clinical dietary recommendations for patients with IBD. However, exclusionary diet interventions have shown some efficacy in relieving symptoms or inducing remission, suggesting more research is needed to fully understand how diet influences disease behavior or combines with other IBD risk factors to promote disease. This review focuses on the associations of various dietary components and IBD risk in clinical studies and genetically susceptible IBD models.