The Misconception About Fiber Intake with Inflammatory Bowel Disease (IBD)

By Meredith Murdock

During my clinical rotation with Children’s National Medical Center, I was able to work with one of the outpatient gastrointestinal registered dietitians. Through this experience, I attended multiple disease focused clinics and observed the dietitian provide patient education for nutrition management. During the inflammatory bowel disease (IBD) clinic, there was a common misbelief around fiber when it came to diet and disease management. Many patients were under the impression that fiber intake should be lowered or omitted completely to care for IBD symptoms. However, this is not the case. It was informative to hear first-hand about some misconceptions that influence the patients and their families so that I could learn to re-educate them to best improve their health.

Inflammatory bowel disease (IBD) is an umbrella term for two conditions: Crohn’s disease and ulcerative colitis, which are both characterized by chronic inflammation in the GI tract. The exact cause for IBD is unknown; however, having a weakened immune system is a large contributor because of how it reduces protection against environmental triggers. There is also a strong correlation within IBD and genetics which is being seen more frequently through family history and the development of an ineffective immune response. Common symptoms of both diseases include chronic diarrhea, abdominal pain, weight loss, fatigue and bloody stools or rectal bleeding.

My preceptor explained that the main difference between Crohn’s disease and ulcerative colitis is the area of damage that occurs within the GI tract. People with Crohn’s disease can have intestinal damage ranging anywhere from the mouth to the anus. The damage is described as patches because of how largely spontaneous it is throughout the GI tract and inflammation from the disease can reach through multiple layers of the gastrointestinal wall. Ulcerative colitis occurs strictly in the large intestine, also known as the colon, and the rectum. Damage is described as continuous because of how it affects the entire area, usually starting in the rectum and spreading into the colon. Inflammation is only present in the innermost layer of the gastrointestinal lining of the colon.

Inflammation in Crohn’s disease vs ulcerative colitis

During my rotation within the clinic, I commonly heard patients blame fiber for IBD flares and struggles. I can understand why they might think that because, unlike other foods, fiber isn’t digested. However, many studies prove that fiber should not be restricted in patients with an active IBD flare unless they are at risk for obstruction. High fiber foods are filled with vitamins, minerals, phytochemicals and healthy fats. Restricting fiber or aiming for a low-fiber diet could lead patients to choose foods higher in sugar, white carbs, animal fat and ultra-processed foods ultimately leaving nutritional gaps.

Fiber can be broken down into two major types, soluble and insoluble. Soluble fiber absorbs water as it moves through the digestive tract, adds bulk and is more fermentable than insoluble fiber. These properties of soluble fiber help guard against both diarrhea and constipation. Those with IBD in general should focus more on soluble fiber, which includes foods such as legumes, beans, nuts, seeds, chia, oats, onions and peeled fruit.

What does someone with an IBD active flare consume? I learned to think more in terms of food’s texture or roughage than fiber content. This is because the rougher the food’s texture is, the more it will irritate the large intestine and increase laxative as well as GI transit time. Therefore, during an active inflammation or for those at risk for obstructing, a low-roughage high fiber diet is used for symptom management. These foods include avocado, banana, peanut or nut butters, hummus, cooked carrots, butternut squash soup, fruit and vegetable smoothies and old-fashioned oats.