Understanding fibre in Crohn’s and colitis
Fibre is often presented as a cornerstone of healthy eating, but for people living with inflammatory bowel disease (IBD), the relationship is more complicated. Some types of fibre can support gut health and ease symptoms, while others may trigger discomfort or worsen a flare. Understanding which forms of fibre to include, and when to reduce or avoid them, can make a real difference to how you feel day to day.
What is fibre?
Fibre is the part of plant foods that the body cannot fully digest. Instead of being broken down in the stomach or small bowel, it travels through to the colon, where gut bacteria interact with it. Fibre is not a single substance. It comes in different forms, and each behaves differently in the gut.
Broadly, fibre can be categorised as soluble or insoluble. Soluble fibre dissolves in water and forms a gel-like substance. It is found in foods such as oats, apples, carrots, and psyllium husk. Insoluble fibre does not dissolve and adds bulk to stool. It is found in foods such as wheat bran, wholegrains, nuts, seeds, and the skins of fruit and vegetables.
Another useful way to think about fibre is whether it is fermentable. Fermentable fibres are those that gut bacteria can break down. This process produces short-chain fatty acids, which may support the gut lining and help regulate the immune response. Non-fermentable fibres pass through the gut largely unchanged.
Why fibre matters in IBD
In Crohn’s disease and ulcerative colitis, the gut lining is often inflamed, and the balance of gut bacteria may be disrupted. The type and amount of fibre you eat can influence both of these factors.
Some fibres may help support the gut lining by feeding beneficial bacteria and producing compounds that reduce inflammation. Others may irritate an already sensitive gut, particularly during a flare or if there is narrowing in the bowel.
Fibre can also affect symptoms such as bloating, pain, diarrhoea, and constipation. However, it is important to remember that feeling better does not always mean inflammation has reduced. Symptoms and underlying gut inflammation do not always align, so any changes to your diet should be discussed with your gastroenterology team.
When fibre may help
Supporting gut bacteria
Fermentable fibres, particularly soluble types, can be broken down by gut bacteria to produce short-chain fatty acids such as butyrate. Butyrate is used as fuel by the cells lining the colon and may help support the gut lining and reduce inflammation. This effect has been observed in people with ulcerative colitis in remission.
Easing constipation
Soluble fibre can help soften stool and support regular bowel movements. This may be helpful for people with Crohn’s disease affecting the colon, or those experiencing constipation as a side effect of medication or reduced food intake.
Supporting overall health
A varied intake of fibre-rich foods provides vitamins, minerals, and plant compounds that contribute to overall health. During periods of remission, gradually including a range of fibre sources may support long-term wellbeing and reduce the risk of other health conditions.
When fibre may cause problems
During a flare
When the gut is inflamed, fibre, especially insoluble types, can be harder to tolerate. Rough or bulky fibre may irritate the gut lining and worsen symptoms such as pain, diarrhoea, and cramping. During flares, many people find it easier to follow a low-fibre or low-residue diet until symptoms settle.
Strictures or narrowing
If Crohn’s disease has caused narrowing in the bowel, high-fibre foods may increase the risk of blockage. Foods with tough skins, seeds, nuts, and fibrous vegetables may be difficult to pass through narrowed areas. In these cases, a low-fibre diet is often recommended, and it is important to work closely with a dietitian.
Bloating and gas
Fermentable fibres can produce gas as they are broken down by gut bacteria. For some people with IBD, this can lead to uncomfortable bloating, especially if gut bacteria are imbalanced or the gut is sensitive. Reducing foods high in fermentable fibres, sometimes called a low-FODMAP approach, may help manage these symptoms in the short term.
Practical takeaways
- Start with small amounts of soluble fibre, such as cooked oats or peeled apples, and increase gradually as tolerated.
- Avoid tough, fibrous foods during flares or if you have narrowing in the bowel. Choose softer, well-cooked vegetables and peeled or stewed fruit instead.
- Keep a simple food and symptom diary to help identify patterns over time. This can be useful when discussing changes with your dietitian or gastroenterology team.
- If bloating or gas is a concern, consider reducing foods high in fermentable fibres temporarily, but do so with guidance to avoid unnecessary restriction.
- Work with a registered dietitian with experience in IBD to tailor your fibre intake to your individual needs, disease activity, and symptoms.
Conclusion
Fibre is neither universally helpful nor harmful in IBD. The type, amount, and timing matter, as does your current disease activity and whether there is any narrowing in the bowel. A flexible approach that adapts to how you are feeling, supported by professional guidance, is the most realistic way to include fibre safely. Nutrition can support stability and quality of life, but it works alongside medical treatment, not in place of it.
References
- Serrano Fernandez V, Seldas Palomino M, Laredo-Aguilera JA, Pozuelo-Carrascosa DP, Carmona-Torres JM. High-fiber diet and Crohn’s disease: systematic review and meta-analysis. Nutrients. 2023;15(14):3114. doi:10.3390/nu15143114
- Firoozi D, Masoumi SJ, Hosseini Asl SMK, et al. Effects of short-chain fatty acid-butyrate supplementation on expression of circadian-clock genes, sleep quality, and inflammation in patients with active ulcerative colitis: a double-blind randomized controlled trial. Lipids Health Dis. 2024;23(1):216. doi:10.1186/s12944-024-02203-z
- Verma B, Manik KA, Verma S, Kumari A, Kumari A, Pinjar MJ. Dietary strategies for gut barrier integrity in inflammatory bowel disease: the impact of fiber and beyond. Cureus. 2026;18(1):e101355. doi:10.7759/cureus.101355
- Hashash JG, Elkins J, Lewis JD, Binion DG. AGA clinical practice update on diet and nutritional therapies in patients with inflammatory bowel disease: expert review. Gastroenterology. 2024;166(3):521-532. doi:10.1053/j.gastro.2023.11.303
This article is intended for informational and educational purposes only. It does not constitute medical advice and should not be used as a substitute for professional medical guidance, diagnosis, or treatment.