The pathogenesis of inflammatory bowel disease (IBD) is thought to be multifactorial, involving a genetically susceptible individual being exposed to a yet-to-be identified environmental trigger or set of triggers. There is growing evidence that IBD may be a disease of Westernization associated with diets high in refined sugars; bread and cereals; proteins, especially dairy; and n-6 polyunsaturated fatty acids acquired from highly processed seed oils. However, the evidence is often low quality, conflicting, and inconclusive.