Effects of a low FODMAP diet on gut microbiota in individuals with treated celiac disease having persistent gastrointestinal symptoms - a randomized controlled trial.

Individuals with celiac disease (CeD) often experience gastrointestinal symptoms despite adherence to a gluten-free diet (GFD). While we recently showed that a diet low in fermentable oligo-, di-, monosaccharides, and polyols (FODMAPs) successfully provided symptom relief in GFD-treated CeD patients, there have been concerns that the low FODMAP diet (LFD) could adversely affect the gut microbiota. Our main objective was therefore to investigate whether the LFD affects the faecal microbiota and related variables of gut health. In a randomized controlled trial GFD-treated CeD adults, having persistent gastrointestinal symptoms, were randomized to either consume a combined LFD and GFD ( n = 39) for four weeks or continue with GFD (controls, n = 36). Compared to the control group, the LFD group displayed greater changes in the overall faecal microbiota profile (16S rRNA gene sequencing) from baseline to follow-up (within-subject β-diversity, P < 0.001), characterized by lower and higher follow-up abundances (%) of genus Anaerostipes (P group < 0.001) and class Erysipelotrichia ( P group = 0.02), respectively. Compared to the control group, the LFD led to lower follow-up concentrations of faecal propionic and valeric acid (GC-FID) in participants with high concentrations at baseline ( P interaction ≤ 0.009). No differences were found in faecal bacterial α-diversity ( P group ≥ 0.20) or in faecal neutrophil gelatinase-associated lipocalin (ELISA), a biomarker of gut integrity and inflammation ( P group = 0.74), between the groups at follow-up. The modest effects of the LFD on the gut microbiota and related variables in the CeD patients of the present study are encouraging given the beneficial effects of the LFD strategy to treat functional GI symptoms. (Registered at clinicaltrials.gov as NCT03678935).