Common Type of Fiber Linked to Gut Inflammation

Fiber is crucial for gut health, but not all fiber is equal. A new study suggests that inulin, a common type of fiber, can exacerbate inflammatory bowel disease.

Fiber is an indigestible carbohydrate found in plant-based foods, such as vegetables, fruits, and whole grains. Consuming enough fiber — 25 to 30 grams per day — can prevent constipation, manage weight, and improve gut health, reducing the risk of obesity and related diseases.

However, a new study published in the Journal of Experimental Medicine suggests that inulin, a common fiber found in plant foods and supplements, can promote intestinal inflammation.

Inulin can worsen IBD

Researchers at Cornell Medicine fed mice with inflammatory bowel disease (IBD) inulin, which led to the increased production of certain bile acids by specific groups of gut bacteria.

These bile acids boosted ILC2 cells' production of an inflammatory protein called IL-5. However, the cells also failed to produce a tissue-protecting protein called amphiregulin.

As a response, the immune system promoted the production of immune cells called eosinophils, further ramping up inflammation and tissue damage.

Previous research has suggested that increased eosinophils may help protect against parasite infections. However, in the IBD model, this chain reaction aggravated intestinal inflammation, weight loss, and other symptoms like diarrhea.

In the study, researchers also examined human tissue, blood, and stool samples from IBD patients. Compared with people without the condition, these patients had higher levels of bile acids in their blood and stool and excessive levels of eosinophils in their intestines.

The results suggest that the dietary uptake of inulin may further exacerbate IBD, the condition characterized by chronic inflammation of the gastrointestinal tract that affects about 2.39 million Americans.

Crohn's disease and ulcerative colitis are the most common IBDs that cause symptoms like abdominal pain, blood stools, and urgency to have a bowel movement. The condition can be debilitating and lead to life-threatening complications.

The new study shows that different types of fiber may influence the microbiota and the body's immune system differently, the authors say.

"These findings could have broader implications for the delivery of precision nutrition to individual patients to promote their overall health based on their unique symptoms, microbiota composition and dietary needs," said senior author David Artis, director of the Jill Roberts Institute for Research in Inflammatory Bowel Disease and director of the Friedman Center for Nutrition and Inflammation at Weill Cornell Medicine.

Can inulin help with IBD?

The findings of a new trial contradict results from some previous studies highlighting the potential therapeutic properties of inulin on IBD patients.

For instance, a 2007 human trial found that inulin supplementation was well-tolerated by ulcerative colitis patients and was associated with an early reduction in fecal calprotectin, a marker for inflammation in the gastrointestinal tract.

A 2024 study in mice suggests that inulin can improve recurrent IBD symptoms by modulating microbiota composition, reducing inflammation, and alleviating endoplasmic reticulum (ER) stress. ER stress occurs when proteins are not properly folded and is a major contributor to the development of IBD.

An ongoing clinical trial examines the effects of inulin in children and adults with IBD. When inulin is broken down by bacteria in the gut, it produces metabolites, including butyrate, which promotes a healthy gut barrier and prevents a leaky gut. The authors point out that individuals with IBD tend to have lower levels of butyrate.

The benefits and risks of inulin

Inulin is found in more than 36,000 plant species, with its primary sources including Jerusalem artichoke, onion, garlic, leek, banana, and barley. It is also a commonly found ingredient in fiber supplements and foods with added fiber.

The effects of inulin may depend on the interaction with the gut microbiome, which varies between people.

The benefits of inulin include raised levels of the good Lactobacillus species and Faecalibacterium prausnitzii, as well as reduced levels of Clostridium species, some of which are potentially pathogenic.

Supplementation with inulin has been shown to improve blood sugar control, reduce "bad" LDL cholesterol, increase satiety, and improve bowel movement frequency and consistency. However, these effects observed in clinical trials were small.

Possible side effects of inulin supplementation can include flatulence, abdominal rumbling or cramping, bloating, and diarrhea.

The findings could pave the way for therapeutic diets that may help ease symptoms and promote gut health, the authors say. Meanwhile, patients with IBD should discuss their dietary choices with their healthcare provider.


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Comments

John Casey
prefix 14 days ago
Wife and I made some LEEK soup a few weeks ago. We never bought a leek before. Only used 1 or 2 inches of it. We both had a lot of bloating and swore to Never Eat Leeks again.