Effects of a FODMAP diet on gut microbiota

Title: Effects of a Low FODMAP Diet on Gut Microbiota in Coeliac Disease

1. Introduction

• Study Objective: Investigate the impact of a low fermentable oligo-, di-, monosaccharides and polyols (FODMAP) diet on gut microbiota in adults with treated coeliac disease (CeD) experiencing persistent gastrointestinal symptoms despite a gluten-free diet (GFD).

• Concern: Previous concerns regarding low FODMAP diets (LFD) affecting gut microbiota and overall gut health.

2. Study Design

• Type: Randomised Controlled Trial.

• Participants:

  • Adults with treated CeD and ongoing gastrointestinal symptoms.

  • Participants must have adhered to a GFD for at least 12 months.

  • Excluded if clinically unstable or with other GI disorders.

• Groups:

  • LFD Group: Combination of low FODMAP and GFD for 4 weeks (n=39).

  • Control Group: Continued GFD without modifications (n=36).

• Methods: Faecal microbiota analysis through 16S rRNA gene sequencing, concentrations of short-chain fatty acids (SCFA), and faecal neutrophil gelatinase-associated lipocalin (NGAL).

3. Results

3.1 Changes in Faecal Microbiota

• Overall Findings:

  • Significant differences were seen in the overall faecal microbiota profiles between the two groups (within-subject β-diversity; P < 0·001).

  • LFD Group Changes:

    • Decreased abundance of genus Anaerostipes (P < 0·001).

    • Increased abundance of class Erysipelotrichia (P = 0·02).

• Bacterial Diversity:

  • No significant changes in faecal bacterial α-diversity (P ≥ 0·20).

3.2 SCFA Concentrations

• Key Findings:

  • The LFD led to significantly lower concentrations of faecal propionic and valeric acid in participants carrying high concentrations at baseline (Pinteraction ≤ 0·009).

• No Significant Differences:

  • No differences in total SCFA, acetic acid, butyric acid concentrations between groups (P < 0.05).

4. Discussion

4.1 Implications for Coeliac Disease Management

• While LFD provided symptom relief in CeD patients, it may pose risks of altering key gut microbiota.

  • Notably beneficial for symptom management as it alleviates functional GI issues.

4.2 Potential Concerns

• Reduction of beneficial taxa, particularly Bifidobacterium, noted in some studies as being adversely affected by LFD.

• Lower SCFA concentrations could indicate dysbiosis which may or may not correlate with symptom severity.

4.3 Future Directions

• Studies should explore long-term effects of LFD and other dietary adjustments beyond the initial reduction phase.

  • Focus on broader microbiota (including fungi) and other gastrointestinal markers.

5. Conclusion

• The study demonstrated that a short-term LFD results in notable, but varied alterations in the gut microbiota of GFD-treated CeD patients.

• Overall, while few uniform changes were detected, results indicate potential individualised responses.

• Findings are encouraging given the benefits reported from the low FODMAP dietary approach to alleviate gastrointestinal symptoms.

Effects of a Low FODMAP Diet on Gut Microbiota in Coeliac Disease

1. Introduction

Study Objective:This study aims to investigate the impact of a low fermentable oligo-, di-, monosaccharides, and polyols (FODMAP) diet on gut microbiota in adults diagnosed with coeliac disease (CeD) who have been treated but continue to experience persistent gastrointestinal symptoms despite adhering to a gluten-free diet (GFD).Concern:There are existing concerns regarding the low FODMAP diet (LFD) potentially resulting in negative affects on gut microbiota composition and overall gut health, as a restriction in certain fermentable carbohydrates may lead to decreased microbial diversity over time, affecting the gut's ecological balance.

2. Study Design

Type:This research was conducted as a randomized controlled trial, allowing for comparison between two dietary approaches.Participants:Subjects included adults diagnosed with treated CeD, who continued to experience gastrointestinal symptoms like bloating, abdominal pain, or altered bowel movements. Remote adherence to a GFD for at least 12 months was required for inclusion. Participants with clinical instability or those having other gastrointestinal disorders were excluded to maintain homogeneity in the study population.Groups:

• LFD Group: Participants followed a stringent low FODMAP and gluten-free diet for a duration of 4 weeks (n=39).

• Control Group: Participants continued with their gluten-free diet without any modifications (n=36).Methods:Faecal microbiota was examined through 16S rRNA gene sequencing, and the concentrations of short-chain fatty acids (SCFA) were measured, alongside the evaluation of faecal neutrophil gelatinase-associated lipocalin (NGAL) as a marker of gut inflammation.

3. Results

3.1 Changes in Faecal Microbiota

Overall Findings:Statistical analysis revealed significant differences in the overall faecal microbiota profiles between the two dietary groups (within-subject β-diversity; P < 0.001).LFD Group Changes:

• There was a notable decrease in the abundance of the genus Anaerostipes, which is typically associated with healthy gut function (P < 0.001).

• Conversely, an increase in the abundance of the class Erysipelotrichia was observed (P = 0.02), which may be related to a shift in microbial composition that lacks beneficial characteristics.

Bacterial Diversity:No significant alterations in faecal bacterial α-diversity were observed, indicating potential stability in the overall diversity during this brief intervention (P ≥ 0.20).

3.2 SCFA Concentrations

Key Findings:Participants on the LFD demonstrated significantly lower concentrations of faecal propionic and valeric acid when baseline levels were high (Pinteraction ≤ 0.009).No Significant Differences:Total SCFA levels, as well as concentrations of acetic acid and butyric acid, showed no significant differences between the dietary groups (P < 0.05), suggesting that while some short-chain fatty acids were affected, the overall production remained relatively stable.

4. Discussion

4.1 Implications for Coeliac Disease Management

While the LFD provided symptomatic relief in patients with CeD, it may pose risks to altering key gut microbiota composition. The diet appears notably beneficial for managing symptoms related to functional gastrointestinal disorders, highlighting a need to cautiously balance dietary modifications.

4.2 Potential Concerns

Some studies have reported a reduction in beneficial taxa, particularly increases in Bifidobacterium, which is crucial for a healthy microbiota, indicating that prolonged adherence to LFD could have adverse effects on microbial balance leading to possible dysbiosis. Lower concentrations of SCFA could suggest a disruption in the gut microbiota community that might not necessarily correlate with symptom severity in every case, necessitating further evaluation.

4.3 Future Directions

Future studies should focus on the long-term effects of LFDs and consider additional dietary adjustments beyond the immediate reduction phase. There is also a need for research that explores a broader spectrum of microbiota—including fungal populations—and other gastrointestinal markers of health and disease states in individuals with CeD.

5. Conclusion

The findings of this study indicate that a short-term low FODMAP diet results in notable yet varied alterations in the gut microbiota of patients with treated coeliac disease on a gluten-free diet. Although few uniform changes were detected, individual responses hint at the complexity of dietary impacts on gut health, emphasizing the promising nature of the low FODMAP dietary approach in alleviating gastrointestinal symptoms in these patients.