The Best Types of Fiber for People With IBD
What Is Fiber and Why Do People With IBD Often Avoid It?
Fiber is a type of carbohydrate that the body cannot digest, naturally found in fruits and vegetables, beans and legumes, nuts, seeds, and whole grains. It passes through our GI tract mostly intact, and plays a number of key roles in maintaining overall health.
On average, those with IBD consume less fiber than those without IBD, according to research published in the April 2021 Journal of the Academy of Nutrition and Dietetics. In fact, less than a quarter of those with IBD are estimated to meet national fiber recommendations per the aforementioned research, and understandably so. Historically, low-fiber diets were widely recommended to those with IBD to limit mechanical irritation to the gut lining, per a paper published in the Lancet Gastroenterology and Hepatology in May 2019. But according to the paper, these recommendations were not based on actual scientific evidence. Instead, they were based on anecdotal reports of patients who felt better after removing fibrous foods from their diets.
Why Fiber Is Important for Those With IBD
While fibrous foods like fresh fruits and vegetables may sound like a bad idea when your GI tract is inflamed, some fiber types found in certain plant foods are gentle on the gut and unlikely to worsen irritation. In fact, higher fiber intakes are actually associated with reduced IBD inflammation and higher remission rates, according to research published in June 2022 in the journal Biomedicines. Additionally, those with IBD have a higher risk of colorectal cancer than the general population, and high fiber intake is thought to be preventive against colorectal cancer, per the Biomedicines research.
Further, a common characteristic among those with IBD is reduced diversity of gut microbes, and an increase in certain bacteria thought to be harmful. High-fiber diets encourage a more diverse and favorable composition of gut microbes, which is associated with improved health outcomes and lower inflammation levels as outlined in the Biomedicines research.
That said, before drastically increasing your fiber intake, it’s important to speak with your healthcare team to ensure it is safe for you to do so, especially if you have stricturing Crohn’s disease, a history of bowel obstruction, or if you recently had surgery for your IBD.
Types of Fiber That Are Beneficial for IBD
Soluble Fiber
Soluble fiber is a gentle type of fiber that helps normalize bowel function. While most people associate fiber with alleviation of constipation, soluble fiber can actually improve diarrhea. According to the Crohn’s & Colitis Foundation, it does this by soaking up water in the GI tract, forming a gel. This gelling property slows the rate of food moving through the GI tract, allowing more time for the intestines to absorb water.
Some types of soluble fiber, like inulin or resistant starch, are fermentable by our gut bacteria, meaning they serve as their food, per research published in the journal Nutrients in November 2022. When our gut bacteria are properly nourished, they produce anti-inflammatory compounds called short-chain fatty acids. According to the Nutrients research, these compounds regulate our immune system, maintain a healthy gut lining, and protect against harmful bacteria.
You can find soluble fiber in the fleshy part of fruits and vegetables and in beans, legumes, nuts, seeds, and certain grains. Some examples of IBD-friendly foods rich in soluble fiber include:
- Oatmeal
- Rice
- Barley
- Polenta
- Potatoes without skin
- Winter and summer squash varieties, cooked and peeled
- Smooth nut butters
- Hummus
- Bananas
Types of Fiber That May Aggravate IBD Symptoms
Insoluble Fiber
Insoluble fiber does not hold onto water and is often referred to as “roughage.” It helps push food through the GI tract more quickly, resulting in a laxative effect, per the American Gastroenterological Association. Insoluble fiber tends to be less fermentable by our gut microbes than soluble fiber, so while it is still a healthy component of the diet, its main role is to provide bulk to stool rather than feeding good gut microbes. You can find insoluble fiber in bran, whole nuts and seeds, leafy greens, and the skins of fruits and vegetables, per Harvard T.H. Chan School of Public Health.
Those actively experiencing IBD symptoms often benefit from reducing their intake of insoluble fiber and replacing it with foods rich in soluble fiber instead. For example, swapping out berries for bananas, or opting for oatmeal rather than bran cereal.
FODMAPs
The low FODMAP diet is an elimination diet used to identify dietary triggers in those with IBS. “FODMAP” is an acronym that stands for “fermentable oligosaccharides, disaccharides, monosaccharides, and polyols,” fancy terms for fibers that are highly fermentable by our gut bacteria. As a by-product of fermentation, gut bacteria produce gas and draw water into the intestines, triggering GI symptoms for some. Foods high in FODMAPs include legumes, wheat, lactose-containing dairy, and certain fruits and vegetables like onions, garlic, artichokes, mushrooms, cauliflower, apples, and peaches.
Everyone’s FODMAP tolerance is unique, so it’s helpful to work with a registered dietitian to pinpoint which FODMAPs may trigger your symptoms specifically. It is also important to note that while avoiding FODMAPs can improve functional IBS-like symptoms for some, this does not necessarily equate to a reduction in GI inflammation, and the low FODMAP diet has not been shown to reduce IBD inflammation, according to the Crohn’s & Colitis Foundation.
It is not advisable to start the low FODMAP diet without guidance from a dietitian, as it is highly nuanced, and avoiding high FODMAP foods for a prolonged period can negatively impact the gut microbiome, according to research published in the journal Microorganisms in November 2020.
How to Increase Your Fiber Intake
When upping your fiber intake, it’s best to start “slow and low,” gradually increasing the amount and variety of fiber-rich foods you eat over time. This allows your GI tract and gut microbes to adjust. Increasing your fiber intake too quickly can lead to bloating, cramping, gas, and bowel irregularity. It is also helpful to lean toward soluble over insoluble fiber sources, which tend to be better tolerated during IBD flares, according to the Crohn’s & Colitis Foundation.
To increase the soluble to insoluble fiber ratio in your diet, try peeling skins off fruits and vegetables before eating or cooking them, and select foods that are soft in texture. Modifying food textures by blending, pureeing, or mashing may also improve your tolerance of the fiber they contain. Lastly, you’ll want to make sure you’re drinking plenty of water to help the fiber move through your GI tract smoothly.
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