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Food processing alters diet digestibility and composition, thereby influencing interactions between host biology, diet, and the gut microbiota. The fecal metabolome offers insight into those relationships by providing a readout of diet-microbiota interactions impacting host health.To determine the effects of consuming a processed diet on the fecal metabolome, and to explore relationships between changes in the fecal metabolome with fecal microbiota composition and gastrointestinal health markers.Secondary analysis of a randomized-controlled trial wherein healthy adults (94% male; 18-61 yr; BMI 26 ± 3 kg.m-2) consumed their usual diet (CON, n = 27) or a Meal, Ready-to-EatTM military ration diet comprised of processed, shelf-stable, ready-to-eat items for 21d (MRE, n = 27). Fecal metabolite profiles, fecal microbiota composition, biomarkers of intestinal barrier function, and gastrointestinal symptoms were measured before and after the intervention. Between-group differences and associations were assessed using nonparametric t-tests, partial least squares discriminant analysis, correlation and redundancy analysis.Fecal levels of multiple dipeptides (Mann-Whitney effect size (ES) = 0.27-0.50) and long-chain saturated fatty acids (ES = 0.35-0.58) increased, whereas, plant-derived compounds (ES = 0.31-0.60) decreased in MRE versus CON (P 0.05; q 0.20). Changes in dipeptides correlated positively with changes in fecal levels of Maillard-reaction products (ρ = 0.29-0.70; P 0.05) and inversely with changes in serum prealbumin (ρ = -0.30 - -0.48; P ≤ 0.03). Multiple bile acids, coffee and caffeine metabolites, and plant-derived compounds were associated with both fecal microbiota composition and gastrointestinal health markers, with changes in fecal microbiota composition explaining 26% of the variability within changes in gastrointestinal health-associated fecal metabolites (P = 0.001).Changes in the fecal metabolomes of adults consuming a Meal, Ready-to-EatTM diet implicate interactions between diet composition, diet digestibility and the gut microbiota as contributing to variability within gastrointestinal responses to the diet. Findings underscore the need to consider both food processing and nutrient composition when investigating the impact of diet-gut microbiota interactions on health outcomes. Clinical trials registration: clinicaltrials.gov NCT02423551. |
