Celiac disease is an immune-mediated condition in which gluten, a protein found in wheat, rye, barley and triticale, causes inflammation in the small intestine. While a gluten-free diet is the only current treatment for celiac disease, it can be low in fiber, a nutrient that has been shown to improve gut microbiota health. This explains why many people with this digestive disease are advised to increase their fiber intake to support gut health.
New research from McMaster University shows that the benefits of fiber in celiac disease may depend on whether the right gut bacteria are present in the small intestine to break it down.
The researchers studied the fecal microbiome composition from 27 people with celiac disease: 16 had been recently diagnosed, and 11 had been diagnosed and were following a gluten-free diet for at least two years. Then compared the results to those of 26 healthy people.
They found that people with celiac disease had reduced expression of enzymes involved in the digestion of resistant starch and fiber and lower concentrations of short-chain fatty acids, which are the product of fiber metabolism by gut bacteria. This was explained by a lack of bacteria from the family Prevotellaceae in the small intestine, which are specialized in degrading fiber and supporting gut healing. These findings suggest that the absence of this key fiber-degrading bacterium is likely due to a persistent alteration in the gut microbiome in celiac disease, rather than to insufficient fiber intake.
The authors went a step further and explored which fiber types are helpful in celiac disease by exposing mice that were genetically susceptible to celiac disease on a gluten-free diet with inulin, a soluble plant fiber found in leeks, garlic, onions, artichokes and some food supplements, or HylonVII, an insoluble fiber from corn starch. Inulin reduced intestinal inflammation and increased short-chain fatty acid production in the gut. By contrast, corn-based resistant starch did not impact the microbiome and promote healing in the way inulin did. These findings suggest that the type of fiber matters in celiac disease and supplementing a gluten-free diet with the right fiber (ie, inulin) could benefit people with celiac disease if the right fiber-degrading bacteria are present in their gut.
To sum up, the new research explains that the small intestine gut microbiome could partly explain why gut symptoms persist in some people with celiac disease following a strict gluten-free diet. Removing gluten alone may not be enough to restore the gut microbiome functions in adult patients with celiac disease. In addition to the gluten-free diet, future management may need to consider restoring the gut microbiome functions with targeted fibers and probiotics with live bacteria that help degrade them.
Reference:
Wulczynski M, Constante M, Galipeau HJ, et al. Small intestinal microbial fiber metabolism dysfunction in celiac disease. Nat Commun. 2026; 17(1):2698. doi: 10.1038/s41467-026-70644-4.
