Nutrition and food items may improve or worsen symptoms in Crohn's disease and ulcerative colitis. Protein malnutrition and vitamin and mineral deficiencies are common, particularly deficiency of iron and vitamin D. Dietary fibres and omega-3 fatty acids are safe, but no evidence supports their use as treatment. The use of probiotics is not encouraged in patients with Crohn's disease, but it may maintain remission in ulcerative colitis. Curcumin, chamomile, and other herbal extracts are promising in the treatment of mild ulcerative colitis, but validation of products and monitoring of side effects are insufficient.