Impact of a Mediterranean diet and physical activity intervention on the gut microbiome and faecal metabolites: findings from the MedEx-UK randomised controlled trial.

Abstract

Diet and physical activity (PA) are potential modulators of the gut microbiome, although research findings are inconsistent, and few studies have explored their combined effects. This study used data from ninety-three participants (forty-seven with pre- and post-intervention samples) from the MedEx-UK randomised controlled trial to investigate the impact of a 24-week Mediterranean diet (MedDiet) intervention, alone or with a PA intervention, on gut microbiome composition and faecal metabolites. Faecal samples were collected pre- and post-intervention from participants in each of three treatment groups: habitual lifestyle (control), MedDiet or MedDiet plus PA. Gut microbiome profiles were generated using 16S rRNA gene sequencing. Faecal SCFA, NMR-derived metabolites and bile acids were quantified. MedDiet scores were significantly increased in both intervention groups v. control (p < 0·001). PA levels did not differ significantly between groups (p = 0·17). There were no significant intervention effects on change in α diversity (Shannon index, p = 0·185), endpoint microbial community composition (p = 0·487), bacterial relative abundance (all p > 0·05), NMR metabolite profiles (p = 0·280), bile acid profiles (p = 0·677) or SCFA concentrations (all p > 0·05). Level of adherence to the MedDiet and specific MedDiet components also showed no associations with microbiome/metabolome datasets. In conclusion, we did not find any effect of a MedDiet intervention alone, or alongside a PA intervention, on the gut microbiome or faecal metabolites. This may be due to methodological factors including the heterogeneity of individual dietary changes in this personalised intervention, causing large inter-individual differences in microbiome responses relative to the overall mean effect of the interventions.