Inulin, the wonder dietary fiber, worsens inflammatory bowel diseases

Abdominal cramps and pain, fatigue, diarrhea, bloating and weight loss – these are the main symptoms of inflammatory bowel disease (IBD), which can be not only disruptive to everyday life, but even debilitating. The incidence of these conditions, which include Crohn’s disease and ulcerative colitis, has increased tenfold in recent decades, and most cases are registered among young people.

Although scientists have realized that this type of condition has a genetic component, not everyone with a family history develops the disease, and to date, the environmental triggers for BII remain largely unknown.

But in a recent study published in the Journal of Experimental Medicine, researchers from Weill Cornell Medicine in New York (USA) discovered something completely unexpected about a certain type of dietary fiber, inulin, which is known to have certain anti-inflammatory properties. and which is found in several healthy foods, such as: garlic, leeks, asparagus or artichokes.

Ubiquitous in the recommendations of nutritionists

Dietary fiber – including inulin, which is a type of soluble fiber – is considered an essential part of a healthy diet for most people and is found in the usual recommendations of nutritionists in an attempt to get us to eat more of it daily.

Gut bacteria convert inulin and other types of dietary fiber into short-chain fatty acids that activate immune cells called regulatory T cells, which help reduce inflammation and have other beneficial effects throughout the body.

This has led to a considerable increase in the use of dietary fiber as an additive in both foods and dietary supplements, and purified inulin or inulin-rich chicory root is often the main source of fiber.

“Inulin is now everywhere, from clinical trials to prebiotic juices,” said the study’s lead author, Dr. Mohammad Arifuzzaman, a postdoctoral associate at Weill Cornell Medicine, who, like his colleagues, expected inulin to have also protective effects in case of intestinal inflammatory diseases. But they found the exact opposite.

It causes a flood of immune cells

In their research on mice, the scientists found that feeding the rodents inulin fiber stimulated specific groups of gut bacteria to produce more bile acids. The increase in the amount of bile acids, in turn, stimulated the production of an inflammatory protein, which triggered an excessive immune response in the body, similar to an allergic reaction.

According to experts, this excessive immune response then exacerbates the inflammation and tissue damage of intestinal lesions and symptoms of inflammatory bowel disease.

Earlier, a 2022 study by the same team of researchers showed that this flood of immune cells called eosinophils, which further increase inflammation and tissue damage, can help protect against parasite infections. However, in inflammatory bowel disease, this chain reaction exacerbated intestinal inflammation, weight loss, and other symptoms, such as diarrhea.

The new findings could change treatments for BII

In patient-based translational studies, the research team also analyzed human tissue, blood and stool samples from the Inflammatory Bowel Disease Research Institute database at Weill Cornell Medicine and found that patients with BII had higher levels of bile acids in the blood and stool, and excessive levels of eosinophils in the gut, compared to people without the condition.

The results suggest that this inflammatory cascade, similar to that seen in inulin-fed mice, is already set in motion in humans with inflammatory bowel disease, and dietary intake of inulin may further exacerbate the disease.

The study authors say these unexpected findings may explain why high-fiber diets often exacerbate inflammatory bowel disease in patients. It may also help scientists develop therapeutic diets to reduce symptoms and gut damage in patients with IBD or related conditions.

Furthermore, research has shown that new therapies are urgently needed for these increasingly common intestinal conditions.

The biologic therapies now available for IBD patients may increase the risk of developing infections or autoimmune diseases, which cause the immune system to attack the body.

“The present study shows that not all fibers are the same in how they influence the body’s microbiota and immune system”

Dr. David Artis, professor of immunology and lead author of the study

Small amounts of inulin are present in a wide variety of fruits and vegetables, including bananas, asparagus, leeks, onions and garlic, but the richest source of inulin is considered chicory root.