This common dietary fiber may cause gut inflammation

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Researchers from Weill Cornell Medicine have uncovered some surprising results about inulin, a type of dietary fiber found in various plants and commonly used in fiber supplements.

While dietary fibers are generally celebrated for their health benefits, this new study suggests that inulin might actually worsen inflammatory bowel disease (IBD) symptoms.

The study’s findings were detailed in a publication dated March 20 in the Journal of Experimental Medicine.

Inulin is naturally present in foods like garlic, leeks, and sunchokes and is often added to processed foods to boost fiber content. It is known to be broken down by gut microbes into compounds that typically benefit the body, such as short-chain fatty acids.

These compounds are crucial for activating immune cells that regulate inflammation. However, the new research indicates that inulin can also stimulate gut microbes to produce bile acids that lead to increased inflammation.

The study shows that inulin prompts the production of IL-33, a protein that activates a particular type of immune cell known as group 2 innate lymphoid cells (ILC2s).

These cells, in turn, initiate an immune response akin to an allergic reaction, which can then exacerbate symptoms in models of IBD, such as weight loss and diarrhea.

Mohammad Arifuzzaman, the study’s lead author and a postdoctoral associate at Weill Cornell Medicine, and his team discovered that inulin-fed mice produced higher levels of certain bile acids.

These acids boosted another inflammatory protein, IL-5, which was produced by the ILC2s. Notably, the ILC2s failed to produce amphiregulin, a protein that typically helps protect tissue.

This imbalance in protein production led to an increase in eosinophils, another type of immune cell that, while protective against parasites as shown in a 2022 study by the same team, can cause further inflammation and tissue damage in the context of IBD.

The team extended their research to humans by analyzing tissue, blood, and stool samples from patients at the Jill Roberts Institute for Research in Inflammatory Bowel Disease Live Cell Bank.

They found that patients with IBD showed similar biochemical markers to the inulin-fed mice, such as elevated bile acids and excessive levels of eosinophils in the intestines.

These findings challenge the conventional wisdom that all dietary fibers are beneficial for gut health.

According to David Artis, the study’s senior author and director of the Jill Roberts Institute for Research in Inflammatory Bowel Disease, “The present study shows that not all fibers are the same in how they influence the microbiota and the body’s immune system.”

The results could explain why some patients with inflammatory bowel diseases experience worsened symptoms when consuming high-fiber diets.

They also highlight the potential for developing therapeutic diets that are specifically tailored to reduce symptoms and promote gut health in patients with IBD, taking into account individual dietary needs and the unique composition of their gut microbiota.

This discovery opens new avenues for treatment options that move beyond the current biologic therapies, which carry risks of infections and autoimmune diseases, offering hope for more personalized and safer approaches to managing these increasingly common digestive disorders.

If you care about inflammation, please read studies about the big cause of inflammation in common bowel disease, and vitamin B may help fight COVID-19 and reduce inflammation.

For more information about nutrition, please see recent studies about new way to halt excessive inflammation, and results showing foods that could cause inflammation.

The research findings can be found in the Journal of Experimental Medicine.

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