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Influence of a 3-months low-calorie Mediterranean diet vs. Vegetarian diet on human gut microbiota and SCFA: the CARDIVEG Study
- Giuditta Pagliai, Edda Russo, Elena Niccolai, Monica Dinu, Vincenzo Di Pilato, Alessandro Magrini, Gianluca Bartolucci, Simone Baldi, Marta Menicatti, Betti Giusti, Rossella Marcucci, Gian Maria Rossolini, Alessandro Casini, Francesco Sofi, Amedeo Amedei
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- Journal:
- Proceedings of the Nutrition Society / Volume 79 / Issue OCE2 / 2020
- Published online by Cambridge University Press:
- 10 June 2020, E177
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Introduction
There is growing interest in understanding how diet can modulate the gut microbiota (GM), including its possible association with disease states. The aim of the present study is to compare in a group of subjects in primary prevention for cardiovascular disease (CVD) the effects of Mediterranean (MD) and Vegetarian (VD) dietary patterns on the GM composition and on the short-chain fatty acids (SCFA) production.
Materials and MethodsTwenty-three clinically healthy subjects (16 F; mean age: 58.6 ± 9.8 years) were randomly assigned to isocaloric MD or VD diets lasting 3-months each and then crossed. Anthropometric measurements, body composition, blood and fecal samples were obtained from each participant at the beginning and at the end of each intervention phase. Next Generation Sequencing (NGS) of 16S rRNA were performed to analyze the GM, while the SCFA were evaluated through the Gas Chromatography-Mass Spectrometry system.
ResultsDietary interventions didn't produce significant diversity in the GM composition at higher ranks (family and above), neither between nor within MD and VD, but they did it at genus level. MD significantly changed the abundance of three genera (Enterohabdus, Lachnoclostridium and Parabacteroides), while VD significantly affected the abundance of four genera (Anaerostipes, Streptococcus, Clostridium sensu stricto and Odoribacter). Comparison of the mean variation of each SCFA between MD and VD showed an opposite and statistically significant trend for propionic acid (+ 10% vs -28%, respectively, p = 0.034). In addition, variations of SCFA resulted to be negatively correlated with changes of some inflammatory cytokines such as VEGF, MCP-1, IL-17, IP-10 and IL-12, only after MD. Finally, correlation analyses showed several associations between changes of genera, clinical and biochemical parameters, after both the dietary interventions.
DiscussionOur study indicates that a short-term dietary intervention with MD or VD does not induce major change in the GM, suggesting that a diet should last for longer periods to scratch the resilience of GM. In addition, the negative association between SCFA and a number of inflammatory cytokines reported only after MD, seems to support the anti-inflammatory properties of the MD. Furthermore, several associations between certain bacterial groups, clinical and biochemical parameters, let us hypothesized that the cardiovascular protection associated with the two diets could be due – at least in part – to a modulation of the GM.
Effects of popular diets on anthropometric and metabolic parameters: an umbrella review of meta-analyses of randomized controlled trials
- Monica Dinu, Giuditta Pagliai, Donato Angelino, Alice Rosi, Margherita Dall'Asta, Letizia Bresciani, Cinzia Ferraris, Monica Guglielmetti, Justyna Godos, Cristian Del Bò, Daniele Nucci, Erika Meroni, Linda Landini, Daniela Martini, Francesco Sofi
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- Journal:
- Proceedings of the Nutrition Society / Volume 79 / Issue OCE2 / 2020
- Published online by Cambridge University Press:
- 10 June 2020, E672
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- Article
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Introduction:
The prevalence of overweight, obesity, and their related complications is increasing worldwide. We aimed to summarise and critically evaluate the effects of different popular diets on anthropometric parameters and metabolic risk factors.
Material and methods:An umbrella review of meta-analyses of randomized controlled trials was conducted according to the Joanna Briggs Institute Umbrella Review Methodology. The review protocol has been registered on PROSPERO (ID: CRD42019126103). Medline, Embase, Scopus, Cochrane Database of Systematic Reviews, and Web of Science were searched from inception to April 2019 to identify meta-analyses of randomized controlled trials that examined the effects of different diets on anthropometric parameters and metabolic risk factors. For each association, we estimated the summary effect size by random-effects and fixed-effects models, the 95% confidence interval, and the 95% prediction interval. We also assessed the between-study heterogeneity and evidence for small-study effects. We further applied standardized methodological criteria to evaluate the epidemiological credibility of the statistically significant associations.
Results:Overall, 80 articles reporting 495 unique meta-analyses were examined, covering a wide range of popular diets: low-carbohydrate (n = 21 articles), high-protein (n = 8), low-fat (n = 9), palaeolithic (n = 2), low glycaemic index/load (n = 12), intermittent energy restriction (n = 6), Mediterranean (n = 11), Nordic (n = 2), vegetarian (n = 9), Dietary Approaches to Stop Hypertension or DASH (n = 6), and portfolio dietary pattern (n = 1). The methodological quality of most articles (n = 65; 81%), evaluated using the AMSTAR-2 questionnaire, was low or critically low. The strength of evidence was generally weak. The most consistent evidence was reported for Mediterranean diet, with suggestive evidence of an improvement in weight, body mass index (BMI), total cholesterol, glucose and blood pressure. Suggestive evidence of an improvement in weight and blood pressure was also reported for DASH diet. Low-carbohydrate, high-protein, low-fat and low-glycaemic index/load diets showed suggestive and/or weak evidence of a reduction in weight and BMI, but contrasting evidence for lipid, glycaemic and blood pressure parameters, suggesting potential risks of unfavourable effects. Finally, evidence for palaeolithic, intermittent energy restriction, Nordic, vegetarian and portfolio dietary patterns was graded as weak or not statistically significant.
Discussion:Most meta-analyses showed low methodological quality and the strength of evidence, assessed using evidence classification criteria, was generally weak. Among all the diets evaluated, Mediterranean diet had the strongest and most consistent evidence of a positive effect on both anthropometric parameters and metabolic risk factors.