A review of the epidemiology of inflammatory bowel disease with a focus on diet, infections and antibiotic exposure.

Inflammatory bowel disease (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), are chronic debilitating diseases that occur in populations around the world. The underlying etiology is thought to be multifactorial. There is a well-defined genetic contribution to the diseases, but this does not fully explain the epidemiology. Environmental factors, including the composition of the gut microbiota, are also important. There is wide geographic variability in the incidence and prevalence of IBD. High incidence rates have been observed in the United Kingdom, Northern Europe, Canada, and the United States. Globally, there is evidence of increasing incidence of CD and UC over time. The rising incidence of IBD in Western countries has generally predated that in developing nations, supporting the hypothesis that 'Westernization' of our lifestyle has led to the increased incidence of IBD. Smoking, antibiotic use, and diet are potentially reversible risk factors for IBD. Recommendations to avoid smoking are appropriate for all people, for numerous reasons. Antibiotic use should be limited to appropriate indications, a recommendation that too is appropriate for all populations. Detangling the relationship between diet, the gut microbiome and IBD raises the potential to reduce the incidence of IBD through dietary modification, an approach that might be considered among those at the highest risk.