Introduction The intestinal microbiota drive inflammation associated with Crohn's disease.1 The composition of the intestinal microbiota can be influenced by prebiotic's such as fructo-oligosaccharides (FOS). Preliminary data suggest that FOS can increase colonic bifidobacteria and induce immunoregulatory dendritic cell (DC) epithelial responses.2

Methods To assess the impact of a diet supplemented with FOS in patients with active Crohn's disease using an appropriately powered randomised, double-blind, placebo-controlled trial. Patients with active Crohn's disease (CDAI ≥ 220, plus one marker of inflammation) were randomised to receive 15 g/day FOS or placebo for 4 weeks. The primary endpoint was clinical response at week 4 (change in CDAI of −70 in the intention-to-treat (ITT) population). Multiple pre-specified secondary endpoints were analysed, including intracellular cytokine staining assessed by flow cytometry (n=27).

Results In total, 103 patients were randomised to receive FOS (n=54) or placebo (n=49). The mean (SD) baseline CDAI was 283 (61.1) and 286 (61.5) in the FOS and placebo groups, respectively (p=0.79). Significantly more patients receiving FOS (n=14.26%) than placebo (n=4.8%) withdrew before the 4-week endpoint (p=0.018). There was no significant clinical benefit of FOS compared to placebo (Abstract 003). Patients receiving FOS, but not placebo, had a reduced proportion of IL-6+ intestinal DC, and increased DC staining of IL-10 (both p<0.05). No effect on DC IL-12 was seen. Throughout the intervention patients receiving FOS had a significantly greater severity of flatulence (FOS mean 10.8, SD 5.7 vs placebo 7.3, 3.6, p=0.004) and rumbling gut (mean 8.3, SD 5.0 vs 6.1, 4.1, p=0.029) compared with placebo.

Conclusion An adequately powered trial of a diet supplemented with FOS in a well defined population of patients with active Crohn's disease showed no clinical benefit despite impacting on DC immunology. Patient withdrawal was greater in patients receiving FOS.