Disentangling the nutrition-microbiota liaison in inflammatory bowel disease

Inflammatory Bowel Disease (IBD) is a set of chronic intestinal inflammatory disorders affecting the gastrointestinal (GI) tract. Beside compromised intestinal barrier function and immune hyperactivation, a common IBD feature is dysbiosis, characterized by a reduction of some strains of Firmicutes, Bacteroidetes, Actinobacteria and an increase in Proteobacteria and pathobionts. Emerging evidence points to diet and nutrition-dependent gut microbiota (GM) modulation, as etiopathogenetic factors and adjuvant therapies in IBD. Currently, no nutritional regimen shows universal efficacy, and advice are controversial, especially those involving restrictive diets potentially resulting in malnutrition. This review provides an overview of the role of macronutrients, dietary protocols and GM modulation in IBD patients. A Western-like diet contributes to an aberrant mucosal immune response to commensal bacteria and impairment of the intestinal barrier integrity, thereby triggering intestinal inflammation. Conversely, a Mediterranean nutritional pattern appears to be one of the most beneficial dietetic regimens able to restore the host intestinal physiology, by promoting eubiosis and preserving the intestinal barrier and immune function, which in turn create a virtuous cycle improving patient adherence to the pattern. Further clinical studies are warranted, to corroborate current IBD nutritional guidelines, and develop more accurate models to move forward precision nutrition and ameliorate patients' quality of life.