Dietary fiber and the microbiome: a key duo still impaired in celiac disease

By Elodie Vaz  | Published on April 13, 2026 | 3 min read


Celiac disease is an autoimmune condition triggered by gluten ingestion, leading to chronic inflammation of the small intestine. This damage alters the intestinal mucosa and impairs nutrient absorption. The only treatment is a strict gluten-free diet, which generally controls symptoms but does not fully restore intestinal function.  

In this context, increased fiber intake is often recommended to support digestion and gut health. However, the effectiveness of this strategy may be limited by a previously underestimated factor: the composition of the gut microbiome.  

Understanding why fiber alone is not enough  

A study conducted by McMaster University and published on March 31 in Nature Communications aimed to evaluate the ability of patients with celiac disease to metabolize dietary fiber, in relation to their microbiome.  

The researchers hypothesized that the benefits of fiber depend not only on intake but also on the presence of bacteria capable of breaking it down.   “Initially, we thought the problem was insufficient fiber intake. Then we discovered that people might not have the right bacteria to use the fiber they are already consuming. Increasing fiber intake alone will not solve the problem if underlying issues with its utilization are not addressed,” explained Mark Wulczynski, first author of the study, in a press release.  

A combined clinical and preclinical approach  

To explore this hypothesis, researchers analyzed the gut microbiome of three groups: newly diagnosed patients, patients on a gluten-free diet for more than two years, and healthy controls.  

Samples of intestinal fluid were examined to identify present bacteria and their genetic capacity to degrade different types of fiber. These data were cross-referenced with dietary fiber intake and objective markers derived from plant DNA detected in stool samples.

In parallel, preclinical models were used to assess the impact of different types of fiber on intestinal healing, particularly inulin and resistant starch (Hylon VII).  

A microbial deficit limiting the effect of fiber  

The results show that patients with celiac disease have a significantly reduced capacity to metabolize fiber in the small intestine. This alteration is linked to a deficiency in bacteria from the Prevotellaceae family, which are involved in fiber degradation, inflammation regulation, and mucosal healing.  

This deficit was observed both in newly diagnosed patients and in those on a long-term gluten-free diet, suggesting a persistent microbiome alteration related to the disease itself.

Moreover, while most participants—whether patients or healthy individuals—consumed less fiber than recommended, celiac patients faced a double disadvantage: insufficient intake and reduced capacity to utilize it.  

Preclinical analyses also revealed that not all fibers are equal. Inulin, found in foods such as bananas, garlic, and chicory root, promoted intestinal healing by stimulating the microbiome. In contrast, Hylon VII showed no significant effect on either the microbiome or tissue repair.  

Toward a symbiotic therapeutic approach  

According to Professor Elena Verdu, senior author of the study, “While a gluten-free diet remains essential […], our findings suggest that future therapies may also need to support the gut microbiome.” She added, “This opens the door to combining dietary strategies such as fiber supplementation with probiotics capable of metabolizing these fibers.”  

This so-called symbiotic approach—combining specific fibers with microbiome modulation—could help restore more complete intestinal function.  

By highlighting the crucial role of bacteria in fiber utilization, this study calls for a rethinking of nutritional recommendations in celiac disease. Beyond gluten exclusion, future therapeutic strategies may rely on an integrative approach targeting both diet and the intestinal microbial ecosystem.  

Further research will be needed to confirm these findings and determine whether restoring both microbiome composition and fiber intake can sustainably improve symptoms and intestinal healing.   

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