Gut microbiota associations with diet in irritable bowel syndrome and the effect of low FODMAP diet and probiotics

Clin Nutr. 2021 Apr;40(4):1861-1870. doi: 10.1016/j.clnu.2020.10.013. Epub 2020 Oct 23.


Background and aims: Diet is both a modulator of the gastrointestinal microbiota and an important therapy in irritable bowel syndrome (IBS). We aimed to comprehensively (i) identify diet-microbiota associations in adults with IBS consuming habitual diet; (ii) assess the impact of two nutritional interventions on the microbiota; and (iii) determine whether baseline microbiota can predict clinical response to diet or probiotic intervention.

Methods: Data were analyzed from 95 individuals with IBS participating in a previously published 4-week 2x2 factorial design randomized controlled trial investigating the impact of the low FODMAP diet (LFD) and co-administration of a probiotic. Diet was assessed at four hierarchical levels and partial 16S rRNA gene sequencing was used to profile the microbiota.

Results: There were numerous diet-microbiota associations especially at the nutrient level, including a negative association between protein and Bifidobacterium abundance (rs = -0.358, p < 0.001). After correction for multiple testing, the significance for this association (q = 0.237) and all others was lost. Low FODMAP diet led to changes in abundance of major saccharolytic genera compared with sham diet, including higher Bacteroides (LFD 34.1% (15.7%) vs sham 23.3% (15.2%), q = 0.01) and lower Bifidobacterium (0.9% (1.0%) vs 2.1%, (2.5%) q = 0.029). Compared with placebo, probiotic supplementation led to higher Lactobacillus (probiotic 0.08% (0.1%) vs placebo 0.03% (0.2%), q < 0.001), and Streptococcus abundance (2.0% (2.2%) vs 0.6% (1.2%), q = 0.001). The probiotic treatment buffered the impact of the low FODMAP diet on Bifidobacterium. Baseline microbiota did not predict clinical response to either intervention.

Conclusions: Although diet modifies the gut microbiota, bivariate correlation analysis may only provide a limited explanation of the complex diet interactions with individual gut bacteria in IBS. Some diet interventions modify the microbiota in IBS.

Trial registry: ISRCTN ( Registered under ISRCTN registry identifier no.ISRCTN02275221.

Keywords: Diet; Dietary pattern; Irritable bowel syndrome; Microbiota; Probiotic.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Diet / methods*
  • Female
  • Gastrointestinal Microbiome / physiology*
  • Humans
  • Irritable Bowel Syndrome / diet therapy*
  • Irritable Bowel Syndrome / drug therapy*
  • Irritable Bowel Syndrome / microbiology
  • Male
  • Probiotics / pharmacology*

Associated data

  • ISRCTN/ISRCTN02275221