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Diet strongly affects human health, partly by modulating gut microbiome composition. We used diet inventories and 16S rDNA sequencing to characterize fecal samples from 98 individuals. Fecal communities clustered into enterotypes distinguished primarily by levels of Bacteroides and Prevotella. Enterotypes were strongly associated with long-term diets, particularly protein and animal fat (Bacteroides) versus carbohydrates (Prevotella). A controlled-feeding study of 10 subjects showed that microbiome composition changed detectably within 24 hours of initiating a high-fat/low-fiber or low-fat/high-fiber diet, but that enterotype identity remained stable during the 10-day study. Thus, alternative enterotype states are associated with long-term diet.

Increased consumption of plant-based foods and decreased consumption of animal-based foods is recommended for healthy diets and sustainable food production. We investigated the effects of partial replacement of dietary animal proteins with plant-based ones on intake of energy-yielding nutrients, fibre, and plasma lipoproteins. This 12-week randomised clinical intervention comprised 107 women and 29 men (20–69 years) in three diet groups with different dietary protein compositions (“ANIMAL”: Animal 70%/plant 30%; “50/50”: Animal 50%/plant 50%; “PLANT”: Animal 30%/plant 70%; all: Protein intake 17 E%). Nutrient intakes were assessed by 4-day food records. Saturated fat intake (E%) was lower and polyunsaturated fatty acid intake (E%) higher in the PLANT and 50/50 groups compared to the ANIMAL group (p < 0.001 for all). Fibre intake was higher in the PLANT (p ˂ 0.001) and 50/50 (p = 0.012) groups. Total and LDL cholesterol were lower in the PLANT than in the ANIMAL group (p = 0.003 for both) but no differences in HDL cholesterol or triglycerides were observed (p > 0.05). Replacing animal protein with plant protein sources in the diet led to an increased fibre intake and improved dietary fat quality as well as blood lipoprotein profile. Flexitarian diets could provide healthy and more sustainable alternatives for the current, predominantly animal-based diets.

RationaleThe impact of the microbiota on the gut-brain axis is increasingly appreciated. A growing body of literature demonstrates that use of dietary fibre and prebiotics can manipulate the microbiota and affect host health. However, the influence on cognition and acute stress response is less well understood.ObjectivesThe objective of this study was to investigate the efficacy of a dietary fibre, polydextrose (PDX), in improving cognitive performance and acute stress responses through manipulation of the gut microbiota in a healthy population.MethodsIn this double-blind, randomised, placebo-controlled, crossover design study, 18 healthy female participants received 12.5 g Litesse®Ultra (> 90% PDX polymer) or maltodextrin for 4 weeks. Cognitive performance, mood, acute stress responses, microbiota composition, and inflammatory markers were assessed pre- and post-intervention.ResultsPDX improved cognitive flexibility as evidenced by the decrease in the number of errors made in the Intra-Extra Dimensional Set Shift (IED) task. A better performance in sustained attention was observed through higher number of correct responses and rejections in the Rapid Visual Information Processing (RVP) task. Although there was no change in microbial diversity, abundance of Ruminiclostridium 5 significantly increased after PDX supplementation compared with placebo. PDX supplementation attenuated the increase of adhesion receptor CD62L on classical monocytes observed in the placebo group.ConclusionsSupplementation with the PDX resulted in a modest improvement in cognitive performance. The results indicate that PDX could benefit gut-to-brain communication and modulate behavioural responses.

Dysbiotic gut microbiota have been implicated in human disease. Diet-based therapeutic strategies have been used to manipulate the gut microbiota towards a more favourable profile. However, it has been demonstrated that large inter-individual variability exists in gut microbiota response to a dietary intervention. The primary objective of this study was to investigate whether habitually low dietary fibre (LDF) v. high dietary fibre (HDF) intakes influence gut microbiota response to an inulin-type fructan prebiotic. In this randomised, double-blind, placebo-controlled, cross-over study, thirty-four healthy participants were classified as LDF or HDF consumers. Gut microbiota composition (16S rRNA bacterial gene sequencing) and SCFA concentrations were assessed following 3 weeks of daily prebiotic supplementation (Orafti® Synergy 1; 16 g/d) or placebo (Glucidex® 29 Premium; 16 g/d), as well as after 3 weeks of the alternative intervention, following a 3-week washout period. In the LDF group, the prebiotic intervention led to an increase in Bifidobacterium (P=0·001). In the HDF group, the prebiotic intervention led to an increase in Bifidobacterium (P<0·001) and Faecalibacterium (P=0·010) and decreases in Coprococcus (P=0·010), Dorea (P=0·043) and Ruminococcus (Lachnospiraceae family) (P=0·032). This study demonstrates that those with HDF intakes have a greater gut microbiota response and are therefore more likely to benefit from an inulin-type fructan prebiotic than those with LDF intakes. Future studies aiming to modulate the gut microbiota and improve host health, using an inulin-type fructan prebiotic, should take habitual dietary fibre intake into account.

Background/objectivesIndividuals with high pre-treatment bacterial Prevotella-to-Bacteroides (P/B) ratio have been reported to lose more body weight on diets high in fiber than subjects with a low P/B ratio. Therefore, the aim of the present study was to examine potential differences in dietary weight loss responses between participants with low and high P/B.Subjects/methodsEighty overweight participants were randomized (52 completed) to a 500 kcal/d energy deficit diet with a macronutrient composition of 30 energy percentage (E%) fat, 52 E% carbohydrate and 18 E% protein either high (≈1500 mg calcium/day) or low ( ≤ 600 mg calcium/day) in dairy products for 24 weeks. Body weight, body fat, and dietary intake (by 7-day dietary records) were determined. Individuals were dichotomized according to their pre-treatment P/B ratio derived from 16S rRNA gene sequencing of collected fecal samples to test the potential modification of dietary effects using linear mixed models.ResultsIndependent of the randomized diets, individuals with high P/B lost 3.8 kg (95%CI, 1.8,5.8; P < 0.001) more body weight and 3.8 kg (95% CI, 1.1, 6.5; P = 0.005) more body fat compared to individuals with low P/B. After adjustment for multiple covariates, individuals with high P/B ratio lost 8.3 kg (95% CI, 5.8;10.9, P < 0.001) more body weight when consuming above compared to below 30 g fiber/10MJ whereas this weight loss was 3.2 kg (95% CI, 0.8;5.5, P = 0.008) among individuals with low P/B ratio [Mean difference: 5.1 kg (95% CI, 1.7;8.6, P = 0.003)]. Partial correlation coefficients between fiber intake and weight change was 0.90 (P < 0.001) among individuals with high P/B ratio and 0.25 (P = 0.29) among individuals with low P/B ratio.ConclusionsIndividuals with high P/B lost more body weight and body fat compared to individuals with low P/B, confirming that individuals with a high P/B are more susceptible to weight loss on a diet rich in fiber.

Background Short-chain fatty acids (SCFAs) derived from gut bacteria are associated with protective roles in diseases ranging from obesity to colorectal cancers. Intake of microbially accessible dietary fibers (prebiotics) lead to varying effects on SCFA production in human studies, and gut microbial responses to nutritional interventions vary by individual. It is therefore possible that prebiotic therapies will require customizing to individuals. Results Here, we explored prebiotic personalization by conducting a three-way crossover study of three prebiotic treatments in healthy adults. We found that within individuals, metabolic responses were correlated across the three prebiotics. Individual identity, rather than prebiotic choice, was also the major determinant of SCFA response. Across individuals, prebiotic response was inversely related to basal fecal SCFA concentration, which, in turn, was associated with habitual fiber intake. Experimental measures of gut microbial SCFA production for each participant also negatively correlated with fiber consumption, supporting a model in which individuals’ gut microbiota are limited in their overall capacity to produce fecal SCFAs from fiber. Conclusions Our findings support developing personalized prebiotic regimens that focus on selecting individuals who stand to benefit, and that such individuals are likely to be deficient in fiber intake. FLeuumVMoUypG_CgDJN_5g Video Abstract

The aim of this study was to determine the effect of plant-based diets on weight loss. Participants were enrolled in a 6-mo, five-arm, randomized controlled trial in 2013 in South Carolina. Participants attended weekly group meetings, with the exception of the omnivorous group, which served as the control and attended monthly meetings augmented with weekly e-mail lessons. All groups attended monthly meetings for the last 4 mo of the study. Diets did not emphasize caloric restriction. Overweight adults (body mass index 25–49.9 kg/m2; age 18–65 y, 19% non-white, and 27% men) were randomized to a low-fat, low-glycemic index diet: vegan (n = 12), vegetarian (n = 13), pesco-vegetarian (n = 13), semi-vegetarian (n = 13), or omnivorous (n = 12). Fifty (79%) participants completed the study. In intention-to-treat analysis, the linear trend for weight loss across the five groups was significant at both 2 (P < 0.01) and 6 mo (P < 0.01). At 6 mo, the weight loss in the vegan group (−7.5% ± 4.5%) was significantly different from the omnivorous (−3.1% ± 3.6%; P = 0.03), semi-vegetarian (−3.2% ± 3.8%; P = 0.03), and pesco-vegetarian (−3.2% ± 3.4%; P = 0.03) groups. Vegan participants decreased their fat and saturated fat more than the pesco-vegetarian, semi-vegetarian, and omnivorous groups at both 2 and 6 mo (P < 0.05). Vegan diets may result in greater weight loss than more modest recommendations. •Prospective studies have found that individuals following a vegan diet have low body mass index.•This randomized trial examined changes in body weight among individuals on one of five plant-based diets.•This study found that vegan diets were more effective for weight loss than other diets.•This study found that vegan diets improved macronutrients more than other diets.

Background/ObjectivesThis study assessed the glycemic index (GI) and glycemic load (GL) of three crackers formulated with different flours: a control cracker (CC) made with conventional flour, one with 30% whole wheat flour substitution (WWC), and another with 30% sunflower seed flour substitution (SFC). This study aimed to explore the impact of these substitutions, which vary in protein and fiber content, on the glycemic responses compared to a reference glucose drink.Subjects/MethodsIn a randomized controlled, crossover design, 11 healthy participants (mean age 23.5 ± 1 years; 7 women; BMI 23 ± 1 kg/m2), consumed cracker meals (CC, WWC, and SFC) each providing 50 g of available carbohydrates, and a 50 g glucose reference in separate sessions.ResultsThe SFC crackers provided low GI and GL values (GI: 53 on the glucose scale, GL: 6 per serving), whereas the WWC and CC crackers provided high GI (GI: 77 and 90 on the glucose scale, respectively) and medium GL values (11 and 12 per serving, respectively). Compared with the glucose reference and CC crackers, only SFC induced lower postprandial glucose concentrations, lower glucose excursions, and lower peak glucose values. All crackers were rated as enjoyable and associated with increased satiety.ConclusionsSFC moderated postprandial glycemic responses compared to CC and the reference (D-glucose), but not WWC. These effects may be attributed to the soluble fibers and protein content of the SFC. These findings suggest potential benefits for body weight management and glycemic control, warranting further investigation of the role of flour substitutions in healthy snack options.Clinical trial registrationThis trial has been registered at Clinicaltrials.gov (NCT05702372).

Prebiotic fibre represents a promising and efficacious treatment to manage pre-diabetes, acting via complementary pathways involving the gut microbiome and viscosity-related properties. In this study, we evaluated the effect of using a diverse prebiotic fibre supplement on glycaemic, lipid and inflammatory biomarkers in patients with pre-diabetes. Sixty-six patients diagnosed with pre-diabetes (yet not receiving glucose-lowering medications) were randomised into treatment (thirty-three) and placebo (thirty-three) interventions. Participants in the treatment arm consumed 20 g/d of a diverse prebiotic fibre supplement, and participants in the placebo arm consumed 2 g/d of cellulose for 24 weeks. A total of fifty-one and forty-eight participants completed the week 16 and week 24 visits, respectively. The intervention was well tolerated, with a high average adherence rate across groups. Our results extend upon previous work, showing a significant change in glycated haemoglobin (HbA1c) in the treatment group but only in participants with lower baseline HbA1c levels (< 6 % HbA1c) (P = 0·05; treatment –0·17 ± 0·27 v. placebo 0·07 ± 0·29, mean ± sd). Within the whole cohort, we showed significant improvements in insulin sensitivity (P = 0·03; treatment 1·62 ± 5·79 v. placebo –0·77 ± 2·11) and C-reactive protein (P FWE = 0·03; treatment –2·02 ± 6·42 v. placebo 0·94 ± 2·28) in the treatment group compared with the placebo. Together, our results support the use of a diverse prebiotic fibre supplement for physiologically relevant biomarkers in pre-diabetes.

The Beta-glucan Effects on Lipid profile, glycemia and inTestinal health (BELT) Study investigated the effect of 3 g/day oat beta-glucans on plasma lipids, fasting glucose and self-perceived intestinal well-being. The Study was an 8-week, double-blind, placebo-controlled, cross-over randomized clinical trial, enrolling a sample of 83 Italian free-living subjects, adherent to Mediterranean diet, with a moderate hypercholesterolemia and a low cardiovascular risk profile. Beta-glucans reduced mean LDL-Cholesterol (LDL-C) levels from baseline by 12.2% (95%CI: −15.4 to −3.8) after 4 weeks of supplementation and by 15.1% (95%CI: −17.8 to −5.9) after 8 weeks of supplementation (p < 0.01 for both comparison and versus placebo). Between baseline and 4 weeks Total Cholesterol (TC) levels showed an average reduction of 6.5% (95%CI: −10.9 to −1.9) in the beta-glucan sequence; while non-HDL-C plasma concentrations decreased by 11.8% (95%CI: −14.6 to −4.5). Moreover, after 8 weeks of beta-glucan supplementation TC was reduced by 8.9% (95%CI: −12.6 to −2.3) and non-HDL-C levels by 12.1% (95%CI: −15.6 to −5.3). Decreses in TC and non HDL-C were significant also versus placebo (respectively p < 0.05 and p < 0.01 to both follow-up visits). Fasting plasma glucose and self-perceived intestinal well-being were not affected by both beta-glucan and placebo supplementation.