Main idea: The LFD combined with B-GOS prebiotic produced a greater symptom response than the sham diet plus placebo, but the addition of 1.4 g/d B-GOS did not prevent the reduction of bifidobacteria. The LFD reduces fecal Actinobacteria and butyrate thus strict long-term use should not be advised.
The low FODMAP diet (LFD) reduces symptoms and bifidobacteria in irritable bowel syndrome (IBS). β-galactooligosaccharides (B-GOS) may reduce the symptoms and increase bifidobacteria in IBS. We investigated whether B-GOS supplementation alongside the LFD improves IBS symptoms while preventing the decline in bifidobacteria. The clinical trial was performed. Patients were randomized to a sham diet with placebo supplement (control) or LFD supplemented with either placebo (LFD) or 1.4 g/d B-GOS (LFD/B-GOS) for 4 weeks. At 4 weeks adequate symptom relief was higher in the LFD/B-GOS group than in the control group; Bifidobacterium concentrations were the same between LFD and LFD/B-GOS, but were lower in the LFD/B-GOS than in the control. The proportion of Actinobacteria was lower in LFD and LFD/B-GOS groups than in the control group. Fecal butyrate was lower in the LFD and LFD/B-GOS groups than in the control group.