When is dietary fiber harmful?

People who suffer from inflammatory bowel disease may soon have access to personalized dietary guidelines to keep them feeling well, thanks to new research on how dietary fiber affects the disease. The research team discovered that certain types of dietary fiber cause an inflammatory response in some patients, causing symptoms to worsen.

IBD symptoms may include abdominal pain, diarrhea, bloody stools, weight loss, late puberty, and a long-term risk of colorectal cancer. The exact cause is unknown, but some risk factors include genetics, diet, environmental factors and changes in the gut microbes.

"We know there are health benefits to consuming dietary fibers and they promote good gut health in healthy individuals, but IBD patients quite frequently complain about a sensitivity when they consume dietary fibers," says Heather Armstrong, lead author. "We really wanted to understand the mechanisms behind this, "he added "By creating this stool test, we are hoping to be able to tell you how to adjust your diet to prevent flares or further worsening," says Eytan Wine, a professor in the U of A's Faculty of Medicine & Dentistry. "It's a dynamic situation so it's possible that a certain food you should avoid now, in a few months you'll be okay to eat that again."

The researchers have identified that specific types of fibers found in foods such as artichoke, chicory roots, garlic, asparagus, and bananas, are especially hard to ferment if certain microbes are missing or malfunctioning, as is often the case for IBD patients.

Fiber has a beneficial anti-inflammatory effect in most healthy people and aids with digestion, but the researchers have found that select unfermented fibers actually increases inflammation and worsens symptoms in some IBD patients.

Reference:

Heather Armstrong et al, Unfermented β-fructan fibers fuel inflammation in select inflammatory bowel disease patients, Gastroenterology, DOI: 10.1053/j.gastro.2022.09.034