Is there an “optimal” diet for prevention of inflammatory bowel disease?

Nutritional epidemiological studies have evolved from a focus of single nutrients to diet patterns to capture the protective role of healthy diets on chronic disease development. Similarly, in inflammatory bowel disease (IBD), a healthy diet may be protective against its development in individuals with genetic susceptibility, but the definitions of the optimal diet pattern deserve further exploration. Hence, this review article presents evidence, mainly from prospective cohort studies, for the role of diet quality based on adherence to dietary guidelines, traditional and modern diet patterns in the prevention of IBD. Findings from a limited number of studies on diet quality suggest that high diet quality scores are associated with lower risk of developing Crohn's disease, but the data are inconsistent for ulcerative colitis (UC). There are signals that a Mediterranean diet pattern reduces the risk of Crohn's disease but, again, the data are inconsistent and further studies are much needed. Finally, the evidence is conflicting regarding the role of food additives, with difficulties in the assessment of their intake, namely non-nutritive sweeteners and emulsifiers, precluding accurate assessment of a relationship with IBD risk. In contrast, emerging evidence for a role of ultra-processed food in the development of Crohn's disease but not UC is identified. Given the potential influence of diet quality, a Mediterranean diet and ultra-processed food intake on the risk of Crohn's disease, assessment and implementation of dietary advice for these patients need to be tailored. The search for an optimal diet for UC remains elusive and further research for increasing the evidence in the area is greatly needed.