Coeliac disease: why fibre really matters in a gluten-free diet
A new study shows that the benefits of fibre in coeliac disease depend on the microbiota and SCFA production, not just on intake.
Coeliac disease and dietary fibre: the interaction between a gluten-free diet and the gut microbiota
A gluten-free diet (GFD) is currently the only effective treatment for coeliac disease. However, long-term adherence to a GFD is frequently associated with nutritional challenges, including an inadequate intake of dietary fibre, with potential implications for gut and metabolic health.
Numerous nutritional guidelines recommend an adequate intake of fibre in coeliac patients, both to maintain gut function and to prevent comorbidities. Recent evidence also suggests that a higher fibre intake may be associated with a reduced risk of developing coeliac autoimmunity.
The role of fibre and SCFA production
Dietary fibre, particularly fermentable fibre, exerts some of its biological effects through microbial fermentation and the resulting production of short-chain fatty acids (SCFAs), primarily:
- acetate,
- propionate,
- butyrate.
SCFAs play a key role in:
- maintaining the integrity of the intestinal barrier,
- providing energy for enterocytes (particularly butyrate),
- modulating the inflammatory response,
- regulating intestinal motility and the microbiota.
In individuals with coeliac disease, however, the microbiota of the proximal small intestine appears to have a reduced capacity to metabolise fibre and produce SCFAs, even in the presence of an adequate dietary intake.
The study on the microbiota, coeliac disease and fibre metabolism
A recent study published in Nature Communications investigated the relationship between coeliac disease, the duodenal microbiota and fibre metabolism, combining clinical and experimental data.
The study included:
- 16 patients with newly diagnosed coeliac disease;
- 11 coeliac patients who had been on a gluten-free diet (GFD) for over 2 years;
- 26 healthy control subjects.
The following were analysed:
- duodenal and faecal samples,
- dietary composition,
- gastrointestinal symptoms,
- SCFA production.
Alterations in the microbiota in coeliac patients
In both patients with untreated coeliac disease and those on a gluten-free diet, the duodenal microbiota showed reduced saccharolytic function, defined as a reduced ability to break down complex carbohydrates and fibre. This functional alteration was associated with a reduction in bacteria known to degrade fibre, particularly those belonging to the Prevotellaceae family.
From a metabolic perspective:
- patients with untreated coeliac disease had significantly reduced faecal levels of SCFAs, particularly acetate and butyrate;
- in patients on a low-fibre diet, a partial normalisation was observed, though levels did not fully return to those seen in healthy controls.
The authors emphasise that these alterations are not attributable solely to a reduced fibre intake, frequently observed in individuals on a low-fibre diet, but reflect a functional impairment of the microbiota.
Experimental evidence on the role of fermentable fibre
The experimental component of the study involved the use of mice genetically predisposed to coeliac disease (HLA-DQ8) that had been sensitised to gluten. Following the gluten exposure phase, the animals were placed on a gluten-free diet with or without fibre supplementation.
Supplementation with inulin, a soluble fibre with a prebiotic effect, resulted in:
- faster healing of the intestinal mucosa,
- a reduction in intraepithelial lymphocytes,
- an improvement in the villus-to-crypt ratio,
- a better overall mucosal damage score.
In germ-free models colonised with species of the genus Prevotella, the administration of inulin increased SCFA production even in the small intestine, confirming that the effect of fibre is closely dependent on the composition of the microbiota.
Clinical implications
Overall, the results suggest that, in the nutritional management of coeliac disease, it is not sufficient simply to increase fibre intake; the function of the gut microbiota must also be taken into account. Targeted nutritional strategies, based on: the selection of fermentable fibres, modulation of the microbiota, any prebiotic interventions, could represent a useful addition to the DSG, with potential benefits for the health of the intestinal mucosa. However, larger-scale and longer-term clinical studies are needed to determine the actual clinical impact of such approaches in nutritional and medical practice.
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Wulczynski, M., Constante, M., Galipeau, H. J., Blom, J., Rueda, G. H., et al. (2026). Small intestinal microbial fiber metabolism dysfunction in celiac disease. Nature Communications. https://doi.org/10.1038/s41467-026-70644-4