No single foodstuff increases the risk of ulcerative colitis or triggers a flare-up. Some foods may, however, individually cause symptoms of the digestive tract. Dietary treatment does not replace medication or surgical treatment but good nutritional state supports recovering from flare-ups and improves general well-being.

While in remission, ulcerative colitis patients can usually eat normal food. Absolute dietary limitations are needed only rarely; usually limitations are individual. It is usually enough to eat less of the foods that cause symptoms. If a food that is essential for nourishment, it is important to find a substitute for it. Otherwise, a limited diet can lead to malnutrition. The removal of the large intestine cures ulcerative colitis, and dietary changes after surgery are due to the removal of the bowel and the ostomy.

In addition to ulcerative colitis, patients can have functional stomach ailments that do not disappear even in remission. Dietary limitations cannot prevent flare-ups, but they may help in alleviating symptoms. No instructions can be about a diet that would fit everyone; the diet is tailored from individually suitable foods.

During flare-ups patients might not have proper appetite, and foods that can normally be eaten may worsen diarrhea and abdominal pains. Foods that contain lots of fiber and are difficult to digest should be left out. For recovery, however, it is important to eat regularly and have a balanced diet. The diet can be boosted with supplements or through a tube, and if there is a risk of bowel perforation, nutrition can be given intravenously. In severe ulcerative colitis the large intestine will be removed and the patient will have an ostomy or a J-pouch. The surgery affects especially maintaining fluid and salt balances. The bowel will eventually adapt; not all dietary changes after surgery are permanent.

During diarrhea it is important to drink enough. Diluted drinks that still contain salts and sugar are best, for example diluted juices, tea, mineral water, beef or vegetable broth and juice soup. If the patient has so-called fat diarrhea, fats need to be decreased in the diet and other foodstuffs increased or dietary supplements advised by a nutritionist used to ensure sufficient energy intake.

In more severe cases, dietary treatment is tailored individually. A nutritionist helps in planning and carrying out the diet. Supplements are used when necessary.