The study examines the effect of a low FODMAP diet in patients with UC in remission but still having GI symptoms (IBS in IBD). 15 patients will be on watchful waiting. 15 patients will be on low FODMAP diet. 15 patients with recieve FODMAPs in their diet.

Patients are randomized to either standard care, low FODMAP diet or a normal FODMAP diet. Run-in on a low FODMAP diet, thereafter parallel design where one arm is assign a blinded food supplement with low FODMAP content and the other arm is assigned a blinded food supplement containing FODMAP. A control group is "watchful waiting".

Symptom reports, blood, and fecal samples are collected.

Inclusion Criteria:

• Colitis ulcerosa in remission (calciprotectin<200 and normal sigmoidoscopy)
• ROM IV criteria fullfilled
• Stable medical therapy

Exclusion Criteria:

• Intake of a low FODMAP diet within the past 6 weeks prior to baseline
• Atypical colitis ulcerosa primarily right sided disease and calciprotectin >50 unless normal sigmoidoscopy
• If diarrhea: Clostridium difficile infection
• Lactose intolerance
• Systemisk or local treatment for CU other than 5-aminosalicylicacid or biological therapy
• Antibiotics within 6 weeks
• Pregnancy
• Activity in UC
• Coeliac disease
• Abnormal transglutaminase
• Eating disorder
• Special diet preventing the low FODMAP diet
• Other GI disease or other disease explaining symptoms
• Medication intake explaining symptoms
• Not able to follow protocol