Exploring changes in the human gut microbiota and microbial-derived metabolites in response to diets enriched in simple, refined, or unrefined carbohydrate-containing foods: a post hoc analysis of a randomized clinical trial

Abstract

Background Dietary carbohydrate type may influence cardiometabolic risk through alterations in the gut microbiome and microbial-derived metabolites, but evidence is limited. Objectives We explored the relative effects of an isocaloric exchange of dietary simple, refined, and unrefined carbohydrate on gut microbiota composition/function, and selected microbial metabolite concentrations. Methods Participants [n = 11; age: 65 ± 8 y; BMI (in kg/m2): 29.8 ± 3.2] were provided with each of 3 diets for 4.5 wk with 2-wk washout, according to a randomized, crossover design. Diets [60% of energy (%E) carbohydrate, 15%E protein, and 25%E fat] differed in type of carbohydrate. Fecal microbial composition, metatranscriptomics, and microbial-derived SCFA and secondary bile acid (SBA) concentrations were assessed at the end of each phase and associated with cardiometabolic risk factors (CMRFs). Results Roseburia abundance was higher (11% compared with 5%) and fecal SBA concentrations were lower (lithocolic acid –50% and deoxycholic acid –64%) after consumption of the unrefined carbohydrate diet relative to the simple carbohydrate diet [false discovery rate (FDR): all P < 0.05), whereas Anaerostipes abundance was higher (0.35% compared with 0.12%; FDR: P = 0.04) after the simple carbohydrate diet relative to the refined carbohydrate diet. Metatranscriptomics indicated upregulation of 2 cellular stress genes (FDR: P < 0.1) after the unrefined carbohydrate diet compared with the simple carbohydrate or refined carbohydrate diets. The microbial expression of 3 cellular/oxidative stress and immune response genes was higher (FDR: P < 0.1) after the simple carbohydrate diet relative to the refined carbohydrate diet. No significant diet effect was observed in fecal SCFA concentrations. Independent of diet, we observed 16 associations (all FDR: P < 0.1) of taxon abundance (15 phylum and 1 genera) with serum inflammatory markers and also with fecal SCFA and SBA concentrations. Conclusions Consuming an unrefined carbohydrate–rich diet had a modest effect on the gut microbiome and SBAs, resulting in favorable associations with selected CMRFs. Simple carbohydrate– and refined carbohydrate–rich diets have distinctive effects on the gut microbiome, suggesting differential mechanisms mediate their effects on cardiometabolic health. This trial was registered at clinicaltrials.gov as NCT01610661.

Habitual Diet Pattern Associations with Gut Microbiome Diversity and Composition: Results from a Chinese Adult Cohort

“…Previously reported evidence supports our findings. Evidence from a randomized diet intervention trial aiming to examine the effect of carbohydrate type on gut microbial composition and function and metabolites showed that Anaerostipes had a higher abundance after a simple carbohydrate diet compared to a refined carbohydrate diet [33]. Due to the role of Anaerostipes as a butyrate producer, low abundance after the consumption of refined carbohydrate foods may contribute to the unfavorable effects of diets rich in refined carbohydrates.…”

Role of Whole Grain Consumption in Glycaemic Control of Diabetic Patients: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

“…Moreover, other metabolites (including lipopolysaccharide, branched-chain amino acid and bile acids) from the gut microbiota may also play an important role in insulin resistance [ 55 ]. For example, Faits et al found that consuming an unrefined carbohydrate diet resulted in a significant increase in abundance of Roseburia , as well as a decreased concentration of secondary bile acid [ 56 ]. Results from another randomized controlled crossover feeding study suggested that whole grain consumption led to significant increases in circulating concentrations of taurolithocholic acid, taurocholic acid, and glycocholic acid; moreover, significant associations between bile acids and HOMA-IR were also found in this study [ 57 ].…”

Health benefits of whole grain: effects on dietary carbohydrate quality, the gut microbiome, and consequences of processing

“…Roseburia abundance was higher and the secondary bile acids lithocholic acid and deoxycholic acid were lower after consumption of the unrefined carbohydrate diet relative to the simple carbohydrate diet. There were no changes in SCFA with either diet (Faits et al., 2020). The most recent study investigated the intake of whole‐grain wheat versus refined wheat in adults with overweight or obesity (van Trijp et al., 2020).…”

“…In a randomized cross‐over study, Faits et al. (2020) fed 11 subjects three diets for a period of 4.5 weeks with a 2‐week washout between diets. The diets were labeled either simple, refined, and unrefined carbohydrate diets, differing in the dominant type of carbohydrate.…”