Differential Effects of Western and Mediterranean-Type Diets on Gut Microbiota: A Metagenomics and Metabolomics Approach

Abstract

Our aim was to determine the effect of diet on gut microbiota, digestive function and sensations, using an integrated clinical, metagenomics and metabolomics approach. We conducted a cross-over, randomised study on the effects of a Western-type diet versus a fibre-enriched Mediterranean diet. In 20 healthy men, each diet was administered for 2 weeks preceded by a 2-week washout diet. The following outcomes were recorded: (a) number of anal gas evacuations; (b) digestive sensations; (c) volume of gas evacuated after a probe meal; (d) colonic content by magnetic resonance imaging; (e) gut microbiota taxonomy and metabolic functions by shotgun sequencing of faecal samples; (f) urinary metabolites using untargeted metabolomics. As compared to a Western diet, the Mediterranean diet was associated with (i) higher number of anal gas evacuations, (ii) sensation of flatulence and borborygmi, (iii) larger volume of gas after the meal and (iv) larger colonic content. Despite the relatively little difference in microbiota composition between both diets, microbial metabolism differed substantially, as shown by urinary metabolite profiles and the abundance of microbial metabolic pathways. The effects of the diet were less evident in individuals with robust microbiotas (higher beta-diversity). To conclude, healthy individuals tolerate dietary changes with minor microbial modifications at the composition level but with remarkable variation in microbial metabolism.

A Fermented Milk Product Containing B. lactis CNCM I-2494 Improves the Tolerance of a Plant-Based Diet in Patients with Disorders of Gut–Brain Interactions

“…The volume of gas within the colon, measured by magnetic resonance, remained constant before and during FMP consumption. This observation, i.e., the effect of the FMP on gas metabolism, without changes in the colonic gas content, is in accordance with previous studies that showed no differences in intracolonic gas volume with dietary interventions that modified gas production [16,17]. Indeed, the gas content is under tight homeostatic control at around 100-200 mL.…”

“…It has been documented that, as compared to a low-residue diet, a high-residue diet increases both the volume of colonic biomass and faecal clearance, conceivably by an increase in the residue load and microbiota proliferation [16,17]. FMP administration may have moderated this effect, but biomass volumes and faecal weight were not measured in the present study, and we cannot determine whether the effect of the FMP on symptoms was related to the downregulation of biomass proliferation.…”

“…Our 4-week FMP intervention had minor effects on faecal microbiota composition. In a previous study, using shotgun metagenomics, we observed that strong dietary interventions for short periods of time have only minor effects on composition, but a considerable impact on microbiota metabolism, as assessed by changes in the microbial metabolic pathways in faecal samples, and the urinary excretion of microbial metabolites [16]. Our findings in this study may also reflect metabolic adaptation to the plant-based diet during FMP consumption, as shown by the reduction in flatulence scores and anal gas evacuations after FMP consumption, linked with the downregulation of some putative hydrogenproducing taxa (Bacteroides, Christensenellaceae, and Prevotellaceae) and the upregulation of some hydrogen-consuming taxa (Methanospherae).…”

“…The main outcomes were gastrointestinal symptoms, number of anal gas evacuations, and volume of anal gas evacuated following a probe meal measured at the end of the run-in phase and the administration phase. During the study, participants were instructed to consume their habitual diet except during the last 3 days of the run-in phase (days [16][17][18] and the administration phase (days 44-46) when a mostly plant-based diet (see below) was administered. Participants were not allowed to consume any fermented dairy products (with or without probiotics) or any tablets, pills, or food supplements containing pre-or probiotics other than those provided during the study.…”

Quantitative GC–TCD Measurements of Major Flatus Components: A Preliminary Analysis of the Diet Effect

“…The volume, production, and elimination of intestinal gas are well understood, and it is also known that the composition of the gas evacuated per anus reflects the metabolic activity of intestinal microbiota [ 1 , 2 , 3 ]. However, despite multiple reports relating the volatilome of feces with several pathologies [ 4 , 5 , 6 , 7 ], the composition of intestinal gas in normal conditions is poorly explored.…”