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Background: The US military Meal, Ready-to-Eat food ration is approved as a nutritionally adequate sole source of nutrition for ≤21 days. However, the ration continuously evolves, requiring periodic reassessment of its influence on nutritional status and health., Objective: To determine the effects of consuming the US Armed Services Meal, Ready-to-Eat ration for 21 days, relative to usual diets, on nutrient intake, and indicators of nutritional status and cardiometabolic health., Design: Parallel-arm, randomized, controlled trial, secondary analysis., Participants: Sixty healthy, weight stable, free-living adults from the Natick, MA, area participated between June 2015 and March 2017., Intervention: Participants were randomized to consume their usual diet for 31days (CON), or a strictly controlled Meal, Ready-to-Eat-only diet for 21 days followed by their usual diet for 10 days (MRE)., Main Outcome Measures: Nutrient intake (absolute and adjusted) throughout the study period, and indicators of nutrition status (vitamins B, D, folate, homocysteine, iron, magnesium, and zinc) and cardiometabolic health (glucose, insulin, and blood lipid levels) before (Day 0), during (Day 10 through Day 21), and after (Day 31) the intervention period., Statistical Analysis Performed: Between-group differences over time were assessed using marginal models. Models for nutritional status and cardiometabolic health indicators were adjusted for age, initial body mass index, and baseline value of the dependent variable., Results: Energy-adjusted fiber; polyunsaturated fatty acids; vitamins A, thiamin, riboflavin, B-6, C, D, and E; and magnesium and zinc intakes all increased in MRE during the intervention and were higher compared with CON (P<0.05), whereas relative protein intake decreased and was lower (P<0.05). Serum triglyceride concentrations averaged 19% (95% CI 0% to 41%) higher in MRE relative to CON during Days 10 to 31 (P=0.05). No statistically significant effects of diet on any other nutritional status or cardiometabolic health indicators were observed., Conclusions: Findings demonstrate that a Meal, Ready-to-Eat ration diet can provide a more micronutrient-dense diet than usual dietary intake aiding in maintenance of nutritional status over 21 days., (Copyright © 2020 Academy of Nutrition and Dietetics. Published by Elsevier Inc. All rights reserved.)

Background: Interactions between diet, stress and the gut microbiome are of interest as a means to modulate health and performance. Here, in vitro fermentation was used to explore the effects of a sudden change in diet, 21 days sole sustenance on the Meal, Ready-to-Eat (MRE) U.S. military combat ration, on inter-species competition and functional potential of the human gut microbiota. Human fecal samples collected before and after MRE intervention or consuming a habitual diet (HAB) were introduced to nutrient-rich media supplemented with starch for in vitro fermentation under ascending colon conditions. 16S rRNA amplicon and Whole-metagenome sequencing (WMS) were used to measure community composition and functional potential. Specific statistical analyses were implemented to detect changes in relative abundance from taxa, genes and pathways. Results: Differential changes in relative abundance of 11 taxa, Dorea, Lachnospira, Bacteroides fragilis, Akkermansia muciniphila, Bifidobacterium adolescentis, Betaproteobacteria, Enterobacteriaceae, Bacteroides egerthii, Ruminococcus bromii, Prevotella, and Slackia, and nine Carbohydrate-Active Enzymes, specifically GH13_14, over the 24 h fermentation were observed as a function of the diet intervention and correlated to specific taxa of interest. Conclusions: These findings suggest that consuming MRE for 21 days acutely effects changes in gut microbiota structure in response to carbohydrate but may induce alterations in metabolic capacity. Additionally, these findings demonstrate the potential of starch as a candidate supplemental strategy to functionally modulate specific gut commensals during stress-induced states. [ABSTRACT FROM AUTHOR]

Background 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 relations by providing a readout of diet–microbiota interactions impacting host health. Objectives The aims were to determine the effects of consuming a processed diet on the fecal metabolome and to explore relations between changes in the fecal metabolome with fecal microbiota composition and gastrointestinal health markers. Methods This was a secondary analysis of a randomized controlled trial wherein healthy adults [94% male; 18–61 y; BMI (kg/m2): 26 ± 3] consumed their usual diet [control (CON), n  = 27] or a Meal, Ready-to-EatTM (Ameriqual Packaging) military ration diet composed of processed, shelf-stable, ready-to-eat items for 21 d (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. Results Fecal concentrations of multiple dipeptides [Mann-Whitney effect size (ES) = 0.27–0.50] and long-chain SFAs (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 concentrations of Maillard-reaction products (ρ = 0.29–0.70; P  < 0.05) and inversely with changes in serum prealbumin (ρ = −0.30 to −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). Conclusions 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. This trial was registered at www.clinicaltrials.gov as NCT02423551. [ABSTRACT FROM AUTHOR]