A Meta-Analysis of the Clinical Use of Curcumin for Irritable Bowel Syndrome (IBS)

TL;DR

This first meta-analysis of curcumin for IBS pooled three randomized controlled trials and found a beneficial but non-significant effect on IBS symptoms compared with placebo. Curcumin appeared safe and well tolerated, but the evidence base was limited and heterogeneous.

Key findings

• In the random-effects meta-analysis of 3 studies and 326 patients, curcumin produced a pooled standardized mean difference from baseline IBS severity rating of −0.466 (95% CI: −1.113 to 0.182, p = 0.158), a beneficial but not statistically significant effect.
• Heterogeneity was high (I² = 85.22%).
• Of the 5 clinical trials reviewed, 3 reported positive and significant effects for curcumin-containing products, while 2 found no significant effects compared with placebo and advised against curcumin monotherapy.
• No adverse events were reported in any of the trials reviewed; the paper notes curcumin is generally safe, with occasional reports of slight giddiness, nausea, and diarrhoea, and possible interactions with anticoagulants at higher doses.

Methods

• Systematic search of PubMed, Medline, Embase, PsychINFO, Web of Science, and Google Scholar using curcumin/turmeric terms AND IBS terms yielded 1080 papers published in English between 1 January 1988 and 1 May 2018; grey literature was searched via Google.
• Inclusion criteria were randomized controlled trial, curcumin as active intervention, participants with IBS, and available efficacy outcome measures; non-placebo-controlled trials were excluded. Five studies were systematically reviewed and 3 were included in the final meta-analysis.
• The primary outcome was the standardized mean difference for mean reduction in IBS symptoms from baseline with curcumin, using per-protocol analysis; estimates were pooled with a random-effects model, and heterogeneity was assessed with I² and Cochran’s Q.

Limitations

• Stated: only three studies were available, so funnel plot and sensitivity analyses were not feasible; inter-study variability in curcumin formulation and IBS diagnosis likely contributed to heterogeneity; curcumin was mixed with at least one other therapeutic or potentially therapeutic material in two analyzed trials, making a curcumin-attributable SMD difficult to quantify; longer follow-up is needed because IBS is chronic and relapsing, and current studies ranged only from 8 to 18 weeks.
• Stated: more robust clinical trials involving a standardized curcumin preparation and larger sample sizes are warranted.
• Evident from the text: the small evidence base, marked heterogeneity, and co-interventions limit confidence in the pooled estimate and in attributing any benefit specifically to curcumin.