Dietary fiber is good, except when it isn’t

Thanks to a new study published in Gastroenterology about how dietary fiber affects disease.

The research team found that certain types of dietary fiber cause inflammatory reaction in some patients, causing worsening of symptoms.

They are now working on developing a stool analysis examine the microbes found in each patient’s gut to predict who will have them negative answerso that they can tailor dietary recommendations and treatment to individual patients.

Approximately 0.7 percent of the Canadian population, or every 150 people have IBDincluding Crohn’s disease and ulcerative colitisand is projected to grow to one percent by 2030.

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

“We know what is there health benefits to dietary fiber intake, and they promote good gut health in healthy people, but IBD patients quite often complain of sensitivity when they consume dietary fiber,” says Heather Armstrong, who started the research as a postdoctoral fellow at University A and is now an associate professor of Internal Medicine at the University of Manitoba and the Canada Integrative Biology Research Chair. “We really wanted to understand the mechanisms behind this.”

“By creating this stool analysis, we hope to be able to tell you how to adjust your diet to prevent an exacerbation or further deterioration,” says Eytan Wynne, a professor in the School of Medicine and Dentistry at the University of A. “It’s a dynamic situation, so it’s possible that certain the food you should avoid now, in a few months you will be able to eat it again.’

Not all fibers are born equal

Unlike most of the food we eat, fiber is not digested in the small intestine. Tiny bacteria and fungi or “microbiota” in the large or large intestine produce enzymes to ferment fiber. Chemically speaking, fiber can be a short string of sugars, such as pectin found in citrus fruits, or a very long and branched structure that is more difficult to ferment.

Researchers have determined that certain types of fiber found in foods such as artichokes, chicory roots, garlic, asparagus and bananas are especially difficult to ferment when certain microbes are missing or malfunctioning, as is often the case in IBD patients.

Fiber has beneficial anti-inflammatory effects in most healthy people and aids digestion, but researchers have found that certain non-fermentable fibers actually increase inflammation and worsen symptoms in some IBD patients.

“We want to start to understand why 20 to 40 percent of patients have a sensitivity,” says Armstrong, “while in another portion of patients, these dietary fibers can actually benefit health and protect against disease and have a very positive effect.”

Both Wein and Armstrong warn of what’s new dietary recommendations does not replace drug treatment, but should complement it so that patients can avoid exacerbations and return to remission more quickly if they develop inflammation.

“I have IBD myself, so I often ask myself questions that I want answered,” says Armstrong. “If we can find a way to reduce the inflammation associated with diet, we may be able to alleviate some of the disease and even save some people from progressing to more serious disease.”