Nutritional and dietary strategy in the clinical care of inflammatory bowel disease.

The incidence and prevalence of inflammatory bowel disease have been increasing for decades and IBD has become a worldwide disease. Epidemiology studies demonstrated higher incidence rates in the more westernized countries. The change of habitual diets in these countries is perceived as the reason for the development of IBD. Besides, molecular biological studies showed some pathogenic substances produced after digestion of daily diet decrease the diversity of intestinal microbiota and cause dysbiosis of microbiome. Then, chronic inflammation occurs in some genetically susceptible subjects and IBD developed. As a result, many researchers started to investigate the potential therapeutic effects of nutrients and dietary intervention on the clinical course and pathogenesis of IBD. Carbohydrates, fats, proteins and fibers are investigated and their molecular roles in the inflammatory process are discovered gradually. The undigested carbohydrates are proved to cause overgrowth of colonic bacteria and inflammation occurs by altering colonic microbiome. ω-3 poly-unsaturated fatty acids are more favored over ω-6 poly-unsaturated fatty acids due to its less pro-inflammatory properties. High fibers produce more short-chain fatty acids in colon and facilitate the diversity of colonic microbiota. Moreover, some dietary interventions were designed and studied with promising results. Low FODMAP is recommended in IBS and is also suggested in patients of IBD with IBS-like symptoms. Specific Carbohydrate Diet was designed for celiac disease at first and is proved to be effective to decrease inflammation and to induce remission by decreasing non-digested carbohydrates into colon. Exclusive Enteral Nutrition has been investigated and is suggested to be the first line of management in pediatric CD in many literatures. Paleolithic diet and semi-vegetarian diet are evaluated and might be beneficial in some clinical settings. These findings are promising but limited to the evidence without high quality level. Some more well-designed studies with randomization and double-blind are needed and the primary endpoints should be more focused on the decrease of inflammation in pathology and mucosal healing in endoscopy instead of relief of the symptoms.