New research from McMaster University published on March 31 reports that the effectiveness of dietary fiber for people with celiac disease depends on the presence of certain gut bacteria. The study found that individuals with celiac disease often lack Prevotellaceae, a bacterial family important for breaking down fiber and supporting gut health.
This finding is significant because it suggests that simply increasing fiber intake may not be enough to improve digestive health in those with celiac disease. Instead, both diet and the composition of the gut microbiome need to be considered.
"Originally, we thought that the problem was that people aren't getting enough fiber. Then we found out that people might not have the right bacteria to use the fiber that they're already eating. Adding more fiber won't be the solution unless you fix the underlying problems with using it," said Mark Wulczynski, first author of the study and postdoctoral fellow at McMaster's Farncombe Nutrition Initiative.
The researchers observed this lack of Prevotellaceae in both newly diagnosed patients and those managing their condition through a gluten-free diet. This indicates ongoing disruptions in gut bacteria are linked to celiac disease itself rather than just dietary habits. The only current treatment for celiac disease is a strict gluten-free diet, but this does not appear to fully restore normal microbiome function.
Senior author Elena Verdu said, "While a gluten-free diet remains essential for celiac disease, our findings suggest future therapies may also need to support the gut microbiome. We found reduced fiber-processing activity in the upper gut, the area damaged in celiac disease, which is surprising because this part of the gut has not traditionally been seen as a major site of fiber metabolism. This opens the door to combining dietary strategies like added fiber with probiotics that can metabolize it."
The study also compared different types of fibers and found that inulin—a type found in foods like bananas and onions—helped heal intestinal injury by feeding beneficial bacteria. In contrast, another common type called Hylon VII did not have this effect.
Researchers analyzed samples from newly diagnosed patients, long-term treated patients, and healthy controls by looking at their small intestinal fluid microbiomes as well as their diets using plant DNA markers from stool samples. Most participants consumed less than Health Canada's recommended daily amount of 25-38 grams of fiber; however, there are no specific guidelines for those with diseases like celiac.
These results suggest future approaches could combine specific fibers with targeted probiotics—a synbiotic approach—to better support recovery and symptom management in people living with celiac disease.
