Comparative metabolomics in vegans and omnivores reveal constraints on diet-dependent gut microbiota metabolite production

TLDR

Agrarian diets are linked to lower disease risk and are thought to shape gut microbiota and metabolome, though the extent of this influence remains debated. The study aimed to disentangle environmental from dietary effects by profiling gut microbiota and host metabolome in Western vegans versus omnivores. The authors compared 16S rRNA sequencing and plasma/urinary metabolomics of healthy vegans and omnivores in an urban U.S. setting.

Abstract

<h3>Objective</h3> The consumption of an agrarian diet is associated with a reduced risk for many diseases associated with a 'Westernised' lifestyle. Studies suggest that diet affects the gut microbiota, which subsequently influences the metabolome, thereby connecting diet, microbiota and health. However, the degree to which diet influences the composition of the gut microbiota is controversial. Murine models and studies comparing the gut microbiota in humans residing in agrarian versus Western societies suggest that the influence is large. To separate global environmental influences from dietary influences, we characterised the gut microbiota and the host metabolome of individuals consuming an agrarian diet in Western society. <h3>Design and results</h3> Using 16S rRNA-tagged sequencing as well as plasma and urinary metabolomic platforms, we compared measures of dietary intake, gut microbiota composition and the plasma metabolome between healthy human vegans and omnivores, sampled in an urban USA environment. Plasma metabolome of vegans differed markedly from omnivores but the gut microbiota was surprisingly similar. Unlike prior studies of individuals living in agrarian societies, higher consumption of fermentable substrate in vegans was not associated with higher levels of faecal short chain fatty acids, a finding confirmed in a 10-day controlled feeding experiment. Similarly, the proportion of vegans capable of producing equol, a soy-based gut microbiota metabolite, was less than that was reported in Asian societies despite the high consumption of soy-based products. <h3>Conclusions</h3> Evidently, residence in globally distinct societies helps determine the composition of the gut microbiota that, in turn, influences the production of diet-dependent gut microbial metabolites.