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Effects of Probiotics on Glycemic Control and Metabolic Parameters in Gestational Diabetes Mellitus: Systematic Review and Meta-Analysis.
Yefet, E, Bar, L, Izhaki, I, Iskander, R, Massalha, M, Younis, JS, Nachum, Z
Nutrients. 2023;15(7)
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The prevalence of gestational diabetes is increasing worldwide. Gestational diabetes mellitus (GDM) increases obesity and future development of type 2 diabetes in mother and child. Previous research has looked at the beneficial effects of probiotics in reducing metabolic diseases, however, these specific benefits on women with GDM are not fully understood yet. This systematic review and meta-analysis of fourteen randomised controlled trials assessed the beneficial effects of probiotics on glycemic control and metabolic parameters in women with GDM. This study separately assessed probiotic bacterial strains such as Lactobacillus acidophilus, Bifidobacterium bifidum, and Lactobacillus casei to understand their beneficial effects on metabolic parameters. This meta-analysis and systematic review suggest that probiotic supplementation could help improve glycemic control, insulin resistance and lipid levels in women diagnosed with GDM. All probiotic strains showed improvements in metabolic parameters when assessed separately. Further robust studies are required to assess the effect of probiotic supplementation on post- and pre-prandial glycemic control in women with GDM. Healthcare professionals can employ the results of this study to understand the therapeutic benefits of probiotics for improving GDM.
Abstract
OBJECTIVES To assess the effects of probiotic supplements on glycemic control and metabolic parameters in women with gestational diabetes mellitus (GDM) by performing a systematic review and meta-analysis of randomized controlled trials. The primary outcome was glycemic control, i.e., serum glucose and insulin levels. Secondary outcomes were maternal weight gain, neonatal birth weight, and lipid parameters. Weighted mean difference (WMD) was used. Cochrane's Q test of heterogeneity and I2 were used to assess heterogeneity. RESULTS Of the 843 papers retrieved, 14 (n = 854 women) met the inclusion criteria and were analyzed. When compared with placebo, women receiving probiotic supplements had significantly lower mean fasting serum glucose, fasting serum insulin, homeostatic model assessment for insulin resistance (HOMA-IR), triglycerides, total cholesterol, and VLDL levels. Decreased neonatal birth weight was witnessed in supplements containing Lactobacillus acidophilus. CONCLUSION Probiotic supplements may improve glycemic control and lipid profile and reduce neonatal birth weight in women with GDM.
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The effect of probiotics on gestational diabetes and its complications in pregnant mother and newborn: A systematic review and meta-analysis during 2010-2020.
Mahdizade Ari, M, Teymouri, S, Fazlalian, T, Asadollahi, P, Afifirad, R, Sabaghan, M, Valizadeh, F, Ghanavati, R, Darbandi, A
Journal of clinical laboratory analysis. 2022;36(4):e24326
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Gestational diabetes (GD) refers to glucose intolerance in pregnant women at 24–28 weeks without a history of diabetes that results in hyperglycaemia. Some studies suggest that probiotics are able to overcome insulin resistance in pregnant women with GD. The aim of this study was to investigate the inhibitory effects of probiotics supplementation on GD among pregnant women based on Randomized Controlled Trial studies during in the last 10 years (2010–2020). This study is a systematic review and meta-analysis of 28 studies. The age range of the pregnant women following the probiotics treatment was 18–40 years. Results show that taking probiotic supplements during pregnancy by women with GD has beneficial effects on the metabolic status, colostrum adiponectin levels, microbiome composition, and the maternal and infant health. However, 4 of the analysed studies did not find any significant effect for the probiotic intervention on the incidence of GD. Authors conclude that more homogeneous studies are needed to generalize the findings of this study. Thus, specific probiotic supplementation may be introduced as one of the adjuvant therapies for GD patients.
Abstract
This study was aimed to evaluate the effect of probiotics consumption on gestational diabetes (GD) and its complications in pregnant mother and newborn. The study was registered on PROSPERO (CRD42021243409) and all the enrolled articles were collected from four databases (Medline, Scopus, Embase, and Google Scholar) as randomized controlled trials (RCTs) from 2010 to 2020. A total of 4865 study participants from 28 selected studies were included in this review. The present meta-analysis showed that the consumption of probiotics supplementation has the potential to decrease GD-predisposing metabolic parameters such as blood glucose level, lipid profile, inflammation, and oxidative markers which may reduce GD occurrence among pregnant women.
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The effects of the Green-Mediterranean diet on cardiometabolic health are linked to gut microbiome modifications: a randomized controlled trial.
Rinott, E, Meir, AY, Tsaban, G, Zelicha, H, Kaplan, A, Knights, D, Tuohy, K, Scholz, MU, Koren, O, Stampfer, MJ, et al
Genome medicine. 2022;14(1):29
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The Mediterranean (MED) diet, high in nuts, vegetables, and legumes and low in red meat intake, is recommended for the prevention of cardiometabolic diseases. It has been reported that adherence to MED dietary patterns is associated with a distinct gut microbiome profile. The main aim of this study was to investigate the effect of MED-based dietary interventions on the gut microbiome composition and function. This study was focused on the analysis of the DIRECT-PLUS trials’ secondary outcomes, including gut microbiome profile, lipid profile, glycaemic control, inflammatory state, and cardiometabolic risk. All eligible participants were randomised in a 1:1:1 ratio, into one of the three intervention groups: healthy dietary guidelines (HDG), MED, and Green-MED, all combined with physical activity accommodation. Results showed that: - the Green-MED diet [an improved version of the healthy MED diet, with increased consumption of plant-based foods and reduced meat intake] induced a prominent change in the gut microbiome composition, driven by the low-prevalent “non-core” fraction of the gut microbiome. - the MED and Green-MED diets improved cardiometabolic markers. These beneficial changes in levels of cardiometabolic biomarkers were associated with a concurrent shift in the gut microbiome composition. Authors conclude that the Green-MED diet has extensive effects on the composition and function of the host gut microbiome, with the latter partially mediating the beneficial effects of the diet on cardiometabolic health.
Abstract
BACKGROUND Previous studies have linked the Mediterranean diet (MED) with improved cardiometabolic health, showing preliminary evidence for a mediating role of the gut microbiome. We recently suggested the Green-Mediterranean (Green-MED) diet as an improved version of the healthy MED diet, with increased consumption of plant-based foods and reduced meat intake. Here, we investigated the effects of MED interventions on the gut microbiota and cardiometabolic markers, and the interplay between the two, during the initial weight loss phase of the DIRECT-PLUS trial. METHODS In the DIRECT-PLUS study, 294 participants with abdominal obesity/dyslipidemia were prospectively randomized to one of three intervention groups: healthy dietary guidelines (standard science-based nutritional counseling), MED, and Green-MED. Both isocaloric MED and Green-MED groups were supplemented with 28g/day walnuts. The Green-MED group was further provided with daily polyphenol-rich green tea and Mankai aquatic plant (new plant introduced to a western population). Gut microbiota was profiled by 16S rRNA for all stool samples and shotgun sequencing for a select subset of samples. RESULTS Both MED diets induced substantial changes in the community structure of the gut microbiome, with the Green-MED diet leading to more prominent compositional changes, largely driven by the low abundant, "non-core," microorganisms. The Green-MED diet was associated with specific microbial changes, including enrichments in the genus Prevotella and enzymatic functions involved in branched-chain amino acid degradation, and reductions in the genus Bifidobacterium and enzymatic functions responsible for branched-chain amino acid biosynthesis. The MED and Green-MED diets were also associated with stepwise beneficial changes in body weight and cardiometabolic biomarkers, concomitantly with the increased plant intake and reduced meat intake. Furthermore, while the level of adherence to the Green-MED diet and its specific green dietary components was associated with the magnitude of changes in microbiome composition, changes in gut microbial features appeared to mediate the association between adherence to the Green-MED and body weight and cardiometabolic risk reduction. CONCLUSIONS Our findings support a mediating role of the gut microbiome in the beneficial effects of the Green-MED diet enriched with Mankai and green tea on cardiometabolic risk factors. TRIAL REGISTRATION The study was registered on ClinicalTrial.gov ( NCT03020186 ) on January 13, 2017.
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A randomized controlled trial for response of microbiome network to exercise and diet intervention in patients with nonalcoholic fatty liver disease.
Cheng, R, Wang, L, Le, S, Yang, Y, Zhao, C, Zhang, X, Yang, X, Xu, T, Xu, L, Wiklund, P, et al
Nature communications. 2022;13(1):2555
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Non-alcoholic fatty liver disease (NAFLD) is a common chronic disease that is associated with the development of type 2 diabetes (T2D). A commonality between the two diseases is the body’s inefficiency to uptake sugar from the blood, known as insulin resistance. Dysbiosis of the gut microbiota has been shown to be involved in NAFLD and T2D. Exercise and dietary modifications have been shown to increase gut microbiota diversity altering the composition, however the extent of this change is poorly understood. This randomised control trial of 115 individuals with NAFLD and insulin resistance aimed to determine the effects of aerobic exercise and a diet comprising of 37-40% carbohydrate, 35-37% fat, and 25-27% protein on gut microbiota diversity, liver fat content and sugar metabolism. The results showed that generally diet and exercise increased gut microbiota diversity and ensured maintenance of gut microbiota associated with healthy outcomes. Liver fat content was decreased the most with diet and exercise and by nearly 50% but not all subjects responded the same with responders and non-responders identified. It was concluded that there is a necessity for personalisation of diet and exercise programmes for the treatment of NAFLD. This study could be used by healthcare professionals to understand that gut microbiota diversity may be improved by diet and exercise, however not everyone may be similarly affected. Until more is understood about the gut microbiota, it may be necessary to try different diet and exercise regimes, which are optimal for each individual.
Abstract
Exercise and diet are treatments for nonalcoholic fatty liver disease (NAFLD) and prediabetes, however, how exercise and diet interventions impact gut microbiota in patients is incompletely understood. We previously reported a 8.6-month, four-arm (Aerobic exercise, n = 29; Diet, n = 28; Aerobic exercise + Diet, n = 29; No intervention, n = 29) randomized, singe blinded (for researchers), and controlled intervention in patients with NAFLD and prediabetes to assess the effect of interventions on the primary outcomes of liver fat content and glucose metabolism. Here we report the third primary outcome of the trial-gut microbiota composition-in participants who completed the trial (22 in Aerobic exercise, 22 in Diet, 23 in Aerobic exercise + Diet, 18 in No Intervention). We show that combined aerobic exercise and diet intervention are associated with diversified and stabilized keystone taxa, while exercise and diet interventions alone increase network connectivity and robustness between taxa. No adverse effects were observed with the interventions. In addition, in exploratory ad-hoc analyses we find that not all subjects responded to the intervention in a similar manner, when using differentially altered gut microbe amplicon sequence variants abundance to classify the responders and low/non-responders. A personalized gut microbial network at baseline could predict the individual responses in liver fat to exercise intervention. Our findings suggest an avenue for developing personalized intervention strategies for treatment of NAFLD based on host-gut microbiome ecosystem interactions, however, future studies with large sample size are needed to validate these discoveries. The Trial Registration Number is ISRCTN 42622771.
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Dietary macronutrients and the gut microbiome: a precision nutrition approach to improve cardiometabolic health.
Jardon, KM, Canfora, EE, Goossens, GH, Blaak, EE
Gut. 2022;71(6):1214-1226
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The global rise in the prevalence of obesity is strongly associated with an increase in the incidence and prevalence of cardiometabolic diseases, including insulin resistance (IR) and type 2 diabetes mellitus. In recent years, advancements have been made in understanding the involvement of the gut microbiome in obesity and related cardiometabolic complications as regulator of host energy and substrate metabolism. This study is a review that discusses the latest research describing interactions between dietary composition, the gut microbiome and host metabolism. Results show that current evidence for developing optimal dietary interventions targeting bodyweight control and IR via the gut microbiota is still in its infancy and does not capture the complexity of the integration of a whole-diet approach, the microbial and the host’s metabolic phenotype. Furthermore, implementation of targeted, precision nutrition intervention strategies or dietary guidelines for individuals or subgroups in public health requires further insight in the mechanisms involved in (non-)response to dietary intervention. Authors conclude that future studies are needed and these should focus on assessing detailed individual phenotyping and gaining insight into the balance between carbohydrate and protein fermentation by the gut microbiota as well as the site of fermentation in the colon.
Abstract
Accumulating evidence indicates that the gut microbiome is an important regulator of body weight, glucose and lipid metabolism, and inflammatory processes, and may thereby play a key role in the aetiology of obesity, insulin resistance and type 2 diabetes. Interindividual responsiveness to specific dietary interventions may be partially determined by differences in baseline gut microbiota composition and functionality between individuals with distinct metabolic phenotypes. However, the relationship between an individual's diet, gut microbiome and host metabolic phenotype is multidirectional and complex, yielding a challenge for practical implementation of targeted dietary guidelines. In this review, we discuss the latest research describing interactions between dietary composition, the gut microbiome and host metabolism. Furthermore, we describe how this knowledge can be integrated to develop precision-based nutritional strategies to improve bodyweight control and metabolic health in humans. Specifically, we will address that (1) insight in the role of the baseline gut microbial and metabolic phenotype in dietary intervention response may provide leads for precision-based nutritional strategies; that (2) the balance between carbohydrate and protein fermentation by the gut microbiota, as well as the site of fermentation in the colon, seems important determinants of host metabolism; and that (3) 'big data', including multiple omics and advanced modelling, are of undeniable importance in predicting (non-)response to dietary interventions. Clearly, detailed metabolic and microbial phenotyping in humans is necessary to better understand the link between diet, the gut microbiome and host metabolism, which is required to develop targeted dietary strategies and guidelines for different subgroups of the population.
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Gut and Reproductive Tract Microbiota Adaptation during Pregnancy: New Insights for Pregnancy-Related Complications and Therapy.
Siena, M, Laterza, L, Matteo, MV, Mignini, I, Schepis, T, Rizzatti, G, Ianiro, G, Rinninella, E, Cintoni, M, Gasbarrini, A
Microorganisms. 2021;9(3)
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During pregnancy, several adaptations occur in the female organism. In fact, from fertilization until delivery, the maternal body changes and activates a series of physiological transformations to welcome the new life. The microbiota as a component of human bodies is subject to these modifications. This study is a review that focused on gut and reproductive tract microbiota variations during physiologic pregnancy and in case of pregnancy complications, particularly gestational diabetes mellitus (GDM), pre-eclampsia (PE), and preterm birth (PTB). Results show that: - during pregnancy, major changes have been seen in mothers’ gut microbiota. Between the first and third trimester of pregnancy, to support the foetus growth, there is a shift towards communities of microbes implicated in energy production and storage. - in nonpregnant women, vaginal microbiota could be classified into five major types, representing the community state types. - meconium’s microbes seems to be dominated by the Enterobacteriaceae family, suggesting prenatally stepwise colonization. - gut microbiota may contribute to enhanced insulin resistance in early pregnancy (1st and 2nd trimester). - microbiota imbalances in PE women are related not only with blood pressure levels but also with markers of kidney dysfunction. Thus, it is of key importance to understand the role of microbiota and other factors involved in the etiopathogenesis of PE - dysbiosis is related to PTB (however, further studies are necessary to better understand the correlation between this pregnancy complication and the specific microbiota alteration). Authors conclude that microbiota modulation could be a novel strategy to reduce the morbidity and mortality related to pregnancy complications in the future.
Abstract
Pregnancy is characterized by maternal adaptations that are necessary to create a welcoming and hospitable environment for the fetus. Studies have highlighted how the microbiota modulates several networks in humans through complex molecular interactions and how dysbiosis (defined as quantitative and qualitative alterations of the microbiota communities) is related to human pathologies including gynecological diseases. This review analyzed how maternal uterine, vaginal, and gut microbiomes could impact on fetus health during the gestational period. We evaluated the role of a dysbiotic microbiota in preterm birth, chorioamnionitis, gestational diabetes mellitus and pre-eclampsia. For many years it has been hypothesized that newborns were sterile organisms but in the past few years this paradigm has been questioned through the demonstration of the presence of microbes in the placenta and meconium. In the future, we should go deeper into the concept of in utero colonization to better understand the role of microbiota through the phases of pregnancy. Numerous studies in the literature have already showed interesting results regarding the role of microbiota in pregnancy. This evidence gives us the hope that microbiota modulation could be a novel strategy to reduce the morbidity and mortality related to pregnancy complications in the future.
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Links between metabolic syndrome and the microbiome.
Gildner, TE
Evolution, medicine, and public health. 2020;2020(1):45-46
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Metabolic syndrome (MetS) is a cluster of co-occurring pathological conditions, characterised by insulin resistance, abdominal obesity, hypertension and dyslipidaemia One possible factor contributing to MetS risk is change in microbiome composition. Diets high in processed foods appear to alter microbiome composition in ways that promote higher fat mass and insulin resistance. Additionally, a sedentary lifestyle decreases microbiome diversity, elevating inflammation and metabolic disease risk. Research on how the microbiome responds to modest, attainable changes in diet and physical activity will help identify which dietary adjustments and exercise types have the greatest potential to protect patients from MetS.
Abstract
Metabolic syndrome (MetS) is a cluster of harmful conditions which occur together, such as insulin resistance, abdominal obesity, and hypertension. The global prevalence of MetS is growing rapidly, with some estimates suggesting over one billion people worldwide experience increased morality and disease rates linked with this syndrome. One possible factor contributing to MetS risk is changes in microbiome composition. Approximately 100 trillion bacteria and other microbes reside in the human intestinal tract, collectively termed the gut microbiome. Humans and microbes share a long evolutionary history, with many of these microbes influencing human health outcomes. However, environmental conditions have changed dramatically with human technological innovations; many of these changes (e.g., diets high in processed foods and sedentary lifestyles) appear to impact human-microbe relationships. In general, recent changes in diet and activity patterns have been linked to decreased microbiome diversity, elevating inflammation and metabolic disease risk and likely promoting the development of MetS. Targeting patient diet or exercise patterns may therefore help doctors better treat patients suffering from MetS. Still, additional work is needed to determine how the microbiome responds to changes in patient activity and diet patterns across culturally and biologically diverse human populations.
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Protective effect of probiotics in patients with non-alcoholic fatty liver disease.
Cai, GS, Su, H, Zhang, J
Medicine. 2020;99(32):e21464
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Non-alcoholic fatty liver disease (NAFLD) is common in people with obesity and is characterised by high amounts of fat stored in the liver. Diet and exercise are the standard treatments, however recent studies have indicated that the gut microbiota may have an important role. This randomised control trial of 140 patients with NAFLD, aimed to assess the effect of probiotics when added to standard therapy for 3 months. The results showed that although gut microbiota, some aspects of liver function, blood lipids and blood sugars were all improved in individuals on standard therapy, there were additional improvements in those on standard therapy plus probiotics. It was concluded that although standard therapy alone is adequate to improve NAFLD, probiotics plus standard therapy was superior to standard therapy alone and effective in treatment of NAFLD. This study could be used by health professionals to justify the addition of probiotics to standard therapy to further improve NAFLD outcomes.
Abstract
To investigate the effects of probiotics on liver function, glucose and lipids metabolism, and hepatic fatty deposition in patients with non-alcoholic fatty liver disease (NAFLD).Totally 140 NAFLD cases diagnosed in our hospital from March 2017 to March 2019 were randomly divided into the observation group and control group, 70 cases in each. The control group received the diet and exercise therapy, while the observation group received oral probiotics based on the control group, and the intervention in 2 groups lasted for 3 months. The indexes of liver function, glucose and lipids metabolism, NAFLD activity score (NAS), and conditions of fecal flora in 2 groups were compared before and after the treatment.Before the treatment, there were no significant differences on alanine aminotransferase (ALT), aspartate aminotransferase (AST), glutamine transferase (GGT), total bilirubin (TBIL), total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), insulin resistance index (HOMA-IR), NAFLD activity score (NAS), and conditions of fecal flora in 2 groups (P > .05). After the treatment, ALT, AST, GGT, TC, TG, HOMA-IR, NAS, and conditions of fecal flora in the observation group were better than those in the control group, and the observation group was better after treatment than before. All these above differences were statistically significant (P < .05).Probiotics can improve some liver functions, glucose and lipids metabolism, hepatic fatty deposition in patients with NAFLD, which will enhance the therapeutic effects of NAFLD.
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Mediterranean diet intervention in overweight and obese subjects lowers plasma cholesterol and causes changes in the gut microbiome and metabolome independently of energy intake.
Meslier, V, Laiola, M, Roager, HM, De Filippis, F, Roume, H, Quinquis, B, Giacco, R, Mennella, I, Ferracane, R, Pons, N, et al
Gut. 2020;69(7):1258-1268
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Evidence suggests that the Mediterranean diet (MD) may help prevent cardiovascular disease (CVD). However, this could be influenced by an individual’s gut microbiome, highlighting a need for personalised nutrition practices. This randomised crossover control trial aimed to evaluate an 8-week personalised MD intervention in 82 overweight and obese subjects, who were at high risk of cardiovascular disease. The results showed that a personalised MD lowered cholesterol, regardless of the amount of energy consumed and the amount of exercise performed and relied upon adherence to the MD. Gut microbiome composition was altered by a MD and although markers for diabetes were not improved overall, there was an improvement in prediabetes in individuals with higher levels of Bacteroides species and lower levels of Prevotella species. It was concluded that a MD may reduce cholesterol and alter the gut microbiome to benefit cardiovascular health. Health professionals could use this study to switch patients to a MD whilst maintaining their energy intake to reduce cardiovascular risk. In order to see maximum benefit, it would be recommended to take a personalised approach and analyse an individual’s gut microbiome in order to tailor recommendations.
Abstract
OBJECTIVES This study aimed to explore the effects of an isocaloric Mediterranean diet (MD) intervention on metabolic health, gut microbiome and systemic metabolome in subjects with lifestyle risk factors for metabolic disease. DESIGN Eighty-two healthy overweight and obese subjects with a habitually low intake of fruit and vegetables and a sedentary lifestyle participated in a parallel 8-week randomised controlled trial. Forty-three participants consumed an MD tailored to their habitual energy intakes (MedD), and 39 maintained their regular diets (ConD). Dietary adherence, metabolic parameters, gut microbiome and systemic metabolome were monitored over the study period. RESULTS Increased MD adherence in the MedD group successfully reprogrammed subjects' intake of fibre and animal proteins. Compliance was confirmed by lowered levels of carnitine in plasma and urine. Significant reductions in plasma cholesterol (primary outcome) and faecal bile acids occurred in the MedD compared with the ConD group. Shotgun metagenomics showed gut microbiome changes that reflected individual MD adherence and increase in gene richness in participants who reduced systemic inflammation over the intervention. The MD intervention led to increased levels of the fibre-degrading Faecalibacterium prausnitzii and of genes for microbial carbohydrate degradation linked to butyrate metabolism. The dietary changes in the MedD group led to increased urinary urolithins, faecal bile acid degradation and insulin sensitivity that co-varied with specific microbial taxa. CONCLUSION Switching subjects to an MD while maintaining their energy intake reduced their blood cholesterol and caused multiple changes in their microbiome and metabolome that are relevant in future strategies for the improvement of metabolic health.
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Effects of a Low-Fat Vegan Diet on Gut Microbiota in Overweight Individuals and Relationships with Body Weight, Body Composition, and Insulin Sensitivity. A Randomized Clinical Trial.
Kahleova, H, Rembert, E, Alwarith, J, Yonas, WN, Tura, A, Holubkov, R, Agnello, M, Chutkan, R, Barnard, ND
Nutrients. 2020;12(10)
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Gut bacteria composition can have an important role in health. Long-term adherence to a plant-based diet can lead to altered gut bacteria compared to omnivores, however how this association is linked to body metabolism is not entirely understood. This randomised control trial of 168 overweight individuals on a vegan diet compared to a control group where individuals followed their usual diet containing animal products, aimed to assess gut microbiota changes and how this may be related to body weight, body composition and the body’s ability to balance blood sugars, over 16 weeks. The results showed that body weight was decreased in the vegan group compared to control group, mainly due to reduced fat mass. Measures of the body’s ability to balance blood sugars was significantly improved in the vegan group. Gut microbiota diversity remained unchanged in the vegan group yet increased in the control group. Several species changes were observed in the vegan and control groups. Faecalibacterium prausnitzii increased in the vegan group and this was related to decreases in body weight and fat mass. A smaller decrease in Bacteroides fragilis compared to control was observed with a low-fat vegan diet and this was also associated to decreased body weight, fat mass and increased blood sugar control. It was concluded that changes in body weight, body composition and the body’s ability to balance blood sugars in overweight adults following a vegan diet are related to gut microbiota changes. This study could be used by healthcare professionals to recommend a vegan diet to overweight adults to aid weight loss and understand how this diet may affect those changes.
Abstract
Diet modulates gut microbiota and plays an important role in human health. The aim of this study was to test the effect of a low-fat vegan diet on gut microbiota and its association with weight, body composition, and insulin resistance in overweight men and women. We enrolled 168 participants and randomly assigned them to a vegan (n = 84) or a control group (n = 84) for 16 weeks. Of these, 115 returned all gut microbiome samples. Gut microbiota composition was assessed using uBiome Explorer™ kits. Body composition was measured using dual energy X-ray absorptiometry. Insulin sensitivity was quantified with the predicted clamp-derived insulin sensitivity index from a standard meal test. Repeated measure ANOVA was used for statistical analysis. Body weight decreased in the vegan group (treatment effect -5.9 kg [95% CI, -7.0 to -4.9 kg]; p < 0.001), mainly due to a reduction in fat mass (-3.9 kg [95% CI, -4.6 to -3.1 kg]; p < 0.001) and in visceral fat (-240 cm3 [95% CI, -345 to -135 kg]; p < 0.001). PREDIcted M, insulin sensitivity index (PREDIM) increased in the vegan group (treatment effect +0.83 [95% CI, +0.48 to +1.2]; p < 0.001). The relative abundance of Faecalibacterium prausnitzii increased in the vegan group (+5.1% [95% CI, +2.4 to +7.9%]; p < 0.001) and correlated negatively with changes in weight (r = -0.24; p = 0.01), fat mass (r = -0.22; p = 0.02), and visceral fat (r = -0.20; p = 0.03). The relative abundance of Bacteroides fragilis decreased in both groups, but less in the vegan group, making the treatment effect positive (+18.9% [95% CI, +14.2 to +23.7%]; p < 0.001), which correlated negatively with changes in weight (r = -0.44; p < 0.001), fat mass (r = -0.43; p < 0.001), and visceral fat (r = -0.28; p = 0.003) and positively with PREDIM (r = 0.36; p < 0.001), so a smaller reduction in Bacteroides fragilis was associated with a greater loss of body weight, fat mass, visceral fat, and a greater increase in insulin sensitivity. A low-fat vegan diet induced significant changes in gut microbiota, which were related to changes in weight, body composition, and insulin sensitivity in overweight adults, suggesting a potential use in clinical practice.