Inflammatory bowel disease (IBD) may result from a disturbance in gut bacteria, and hence, diet plays an important role in modifying the gut's microbial content. Many patients with IBD modify their diet to control their symptoms by excluding foodstuffs that they think are responsible for disease exacerbation. Carbohydrate-restrictive diets that reduce intake of complex sugars, gluten-free diets that eliminate the protein responsible for intestinal sensitivity, or low-residue diets that curtail intake of insoluble plant fibres have all been suggested to be beneficial. The Paleolithic diet and fat-restrictive diets have been advocated to reduce intestinal inflammation, while lactose-free and vegetarian diets may also reduce intestinal symptoms. The lack of robust clinical data does not allow prescriptive recommendations, but knowledge about dietary factors that modify the gut's bacteria and cause aggravation of intestinal symptoms may help patients and their carers to modify their food intake and, thus, aid in their treatment.