Systematic review with meta-analysis: effect of fibre supplementation on chronic idiopathic constipation in adults

Summary Background Chronic idiopathic constipation is a common symptom-based gastrointestinal disorder responsible for a substantial economic health service burden. Current guidelines recommend the use of fibre as a first-line treatment. Aim To investigate the effect of fibre (including prebiotic) supplementation on global symptom response, stool output, gut microbiota composition and adverse events in adults with chronic idiopathic constipation. Methods Medline, EmBase, Web of Science, Scopus and the Cochrane central register of controlled trials were searched through to February 2016. Conference proceedings from 2003 to 2015 were hand-searched. There were no language restrictions. Forest plots with 95% CIs were generated using a random-effects model. Results The search strategy generated 1072 citations, of which seven individual randomised controlled trials were eligible. Overall, 113 of 147 (77%) patients assigned to fibre responded to therapy, compared with 61 of 140 (44%) allocated to placebo (RR of success to respond 1.71, 95% CI 1.20–2.42, P = 0.003). Fibre significantly increased stool frequency (SMD, standardised mean difference = 0.39; 95% CI 0.03–0.76; P = 0.03) and softened stool consistency (SMD = 0.35; 95% CI 0.04–0.65; P = 0.02) compared with placebo. Flatulence was significantly higher with fibre compared to placebo (SMD 0.56, 0.12–1.00, P = 0.01). Overall quality of evidence was low. Conclusions This meta-analysis demonstrates that fibre is moderately effective, but also causes moderate gastrointestinal side effects. However, these findings need to be treated with caution due to a high risk of bias. Accordingly, further large, methodologically rigorous trials are required, before any definitive recommendation regarding its risk–benefit profile can be made. PROSPERO registration number CRD42014007005.