Ulcerative colitis diet: what to eat during a flare-up and remission

What is ulcerative colitis and how does it affect digestion?

Ulcerative colitis causes continuous inflammation of the inner lining of the large intestine. Crohn’s disease can affect any part of the digestive tract; ulcerative colitis is limited to the colon and rectum [1].

Both are forms of inflammatory bowel disease. In both, it is worth keeping an eye on what you eat and on possible deficiencies during flare-ups, as well as adapting foods to your symptoms [1]. Treatment approaches for Crohn’s disease and ulcerative colitis can differ [1].

The most common symptoms are diarrhoea with mucus or blood, cramping pain before going to the toilet and tenesmus, the feeling of not having finished emptying your bowels.

During a flare-up, intestinal losses and eating less can raise the risk of malnutrition. The European clinical nutrition guideline recommends assessing this risk from diagnosis and regularly thereafter [1].

What should you eat during an ulcerative colitis flare-up?

When the disease is fully active, the priority is that you manage to eat enough despite the discomfort. If some foods make you feel worse, try soft textures and smaller portions. You do not need to remove all fibre as a rule [2].

Protein needs increase. The European clinical nutrition guideline puts needs at 1.2-1.5 g per kilogram of body weight per day during a flare-up, compared with around 1 g in remission [1]. You can reach this with grilled chicken or turkey, fresh hake or cod, boiled eggs or a French omelette and soft tofu.

Get energy from easily digested carbohydrates. White rice, boiled or steamed potato, pasta and toasted white bread provide energy without overloading the bowel.

Vegetables and fruit according to tolerance. If raw ones upset you, try cooked, peeled carrot or apple. The texture can help you eat; widen the variety again when you feel better [2].

Hydration. With diarrhoea you can lose water and salts. Drink often, and talk to your team if you are passing large volumes of stool or cannot replace fluids [1].

When you come out of a flare-up

When the flare-up subsides, go back gradually to a varied diet. Keeping to a very limited diet for months can make it harder to meet your nutritional needs [1].

In remission, a healthy eating pattern adapted to your tolerance is recommended [1]. The American Gastroenterological Association proposes a Mediterranean pattern, with fruit, vegetables, pulses, whole grains and olive oil [2]. The 2025 European consensus presents it as a possible addition to treatment to maintain remission in ulcerative colitis, although the evidence is still limited [3].

Returning to variety is done step by step. First, a wider variety of cooked vegetables, peeled fruit and mashed or blended pulses. Then wholegrains, ground seeds and salad, watching how each change sits with you. If you tolerate dairy, you can have up to three servings a day, preferably plain and unsweetened, such as plain yoghurt and kefir, which provide calcium.

Which foods to limit and how to try them again

In ulcerative colitis there is no fixed list of foods to remove. Some people notice more discomfort with fat, spicy food or a lot of fibre during a flare-up. Adjust each food group to your symptoms and avoid prolonged exclusions without advice [1] [2].

Foods you avoided during the flare-up can come back as symptoms ease, gradually and according to tolerance. If lactose gives you more diarrhoea or gas, try lactose-free milk and discuss the changes with your registered dietitian-nutritionist.

In remission, prioritise minimally processed foods and limit your regular intake of ultra-processed products. The link between some emulsifiers and the risk of developing inflammatory bowel disease is still being studied; it does not allow a specific flare-up to be attributed to them [1].

Is there a diet that prevents flare-ups?

In ulcerative colitis, no diet is recommended on its own to induce remission of a flare-up [3]. The Mediterranean pattern can be considered as support for treatment to maintain remission. Decisions about medication are for your gastroenterologist [3].

Broad exclusion diets are not a general approach for ulcerative colitis. Cutting out gluten without coeliac disease, or dairy without a specific reason, can limit your diet. If you need a specific intervention, plan it with your clinical team and a registered dietitian-nutritionist experienced in inflammatory bowel disease [3].

The low-FODMAP diet answers a different need. In remission, it can ease functional symptoms similar to those of irritable bowel syndrome; it is not used to treat inflammation [3]. The exclusion phase lasts 2 to 6 weeks, with an end date agreed from the start. After that, reintroduce foods under supervision. In consultations, the question of what to do if gas or bloating persists comes up often.

Which nutrients and supplements should you monitor?

With ulcerative colitis, some micronutrients are often low, because of bleeding, inflammation or an overly restrictive diet. The European clinical nutrition guideline recommends checking them regularly, including in remission, at least once a year [1].

Anaemia from iron deficiency can be linked to intestinal bleeding. If you already have anaemia, your doctor prescribes iron after assessing your blood tests. The European guideline considers intravenous iron if the disease is active, if you cannot tolerate oral iron or if haemoglobin is below 10 g/dl [1].

If you take corticosteroids or are having a flare-up, your clinical team assesses vitamin D, calcium and bone health to prevent osteoporosis [1]. With sulfasalazine or methotrexate, folic acid may be prescribed, and your doctor decides this [1].

Probiotics are not routinely recommended in ulcerative colitis [1]. Prebiotic supplements are not routinely recommended either [1]. If you need any supplement, your doctor or registered dietitian-nutritionist will prescribe it. Do not replace your treatment on your own.

Common mistakes we see in consultations

• Staying on the flare-up diet for months afterwards. Rice, chicken and baked apple work for a few weeks. Kept up in remission, they leave out fruit, vegetables, pulses and grains that you already tolerate.
• Removing foods out of fear and never trying them again. One after another, until the plate is down to five foods and iron, calcium or protein start to run short.
• Dropping dairy without having tried it. Cutting it out by habit reduces calcium, just when corticosteroids already compromise it. If lactose bothers you, there is lactose-free milk, yoghurt and mature cheese.