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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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A whole-grain diet reduces peripheral insulin resistance and improves glucose kinetics in obese adults: A randomized-controlled trial.
Malin, SK, Kullman, EL, Scelsi, AR, Haus, JM, Filion, J, Pagadala, MR, Godin, JP, Kochhar, S, Ross, AB, Kirwan, JP
Metabolism: clinical and experimental. 2018;82:111-117
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Literature shows that dietary whole-grain intake is associated with a lower incidence of type 2 diabetes. The aim of the study was to investigate the association between a whole-grain diet and insulin resistance and glucose use in individuals at risk for type 2 diabetes. The study was a randomized, double-blind, controlled crossover trial involving fourteen middle-aged, obese adults at risk for diabetes. Randomisation was carried out prior to metabolic testing. Results indicate that whole-grain intake as part of a mixed-meal diet significantly improved post-prandial (after a meal) glucose metabolism in middle-aged obese adults. Furthermore, both whole-grain and refined-grain interventions induced about 3–6% weight and fat loss. Authors conclude that whole-grain intake effectively promotes glycaemic control by improving insulin action.
Abstract
BACKGROUND Whole-grain intake is associated with lower risk of type 2 diabetes but the mechanisms are unclear. PURPOSE We tested the hypothesis that a WG diet reduces insulin resistance and improves glucose use in individuals at risk for type 2 diabetes compared with an isocaloric-matched refined-grain diet. METHODS A double-blind, randomized, controlled, crossover trial of 14 moderately obese adults (Age, 38 ± 2 y; BMI, 34.0 ± 1.1 kg/m2). Insulin resistance and glucose metabolism was assessed using an oral glucose tolerance test combined with isotopic tracers of [6,6-2H2]-glucose and [U-13C]-glucose, and indirect calorimetry. Peripheral and hepatic insulin resistance was assessed as 1/(rate of disposal/insulin), and endogenous glucose rates of appearance (Ra) iAUC60-240 × insulin iAUC60-240, respectively. Both diets met ADA nutritional guidelines and contained either whole-grain (50 g per 1000 kcal) or equivalent refined-grain. All food was provided for 8 wk. with an 8-10 wk. washout period between diets. RESULTS Post-prandial glucose tolerance, peripheral insulin sensitivity, and metabolic flexibility (insulin-stimulated - fasting carbohydrate oxidation) improvements were greater after whole-grain compared to the refined-grain diet (P < 0.05). Compared to baseline, body fat (~2 kg) and hepatic Ra insulin resistance was reduced by both diets, while fasting glucose and exogenous glucose-meal were unchanged after both interventions. Changes in peripheral insulin resistance and metabolic flexibility correlated with improved glucose tolerance (P < 0.05). CONCLUSION Whole-grains reduced diabetes risk and the mechanisms appear to work through reduced post-prandial blood glucose and peripheral insulin resistance that were statistically linked to enhanced metabolic flexibility.
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A randomised controlled intervention trial evaluating the efficacy of a Mediterranean dietary pattern on cognitive function and psychological wellbeing in healthy older adults: the MedLey study.
Knight, A, Bryan, J, Wilson, C, Hodgson, J, Murphy, K
BMC geriatrics. 2015;15:55
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Age-related mental decline is an increasing global health problem. Dementia and Alzheimer’s Disease are progressive conditions currently viewed as incurable with no lasting pharmaceutical options. Recent evidence has indicated that diet and lifestyle may help to delay the onset and progression of mental decline. This randomised controlled trial (RCT) will aim to assess the effect of a six months dietary intervention on several mental outcomes, cardiovascular changes and general well being for subjects aged sixty-five and older. The RCT will compare the Mediterranean diet (MedDiet) with continued habitual diet (HabDiet). The MedDiet subjects will follow the traditional Cretan Mediterranean diet. Compliance will be assessed using food questionnaires and multiple blood markers. This RCT will be one of the first worldwide to provide evidence for the cause-effect relationship between the MedDiet and age-related mental function in a healthy older adults. The RCT has recruited 166 participants so will provide robust evidence. Results have yet to be published.
Abstract
BACKGROUND The incidence of age-related cognitive decline is rising considerably around the world. There is evidence from a number of recent cross-sectional and prospective studies indicating positive associations between the Mediterranean dietary pattern (MedDiet) and improved cognitive outcomes among the elderly including, reduced age-related cognitive decline and enhanced age-related cognitive performance. However, to date no study has validated these associations in healthy older adult populations (≥65 years and above) with randomised evidence. The main aim of the present study is to provide justified evidence regarding the efficacy of a MedDiet approach to safely reduce the onset of cognitive decline, and promote optimal cognitive performance among healthy older adults using rigorous, randomised intervention methodology. METHODS/DESIGN MedLey is a 6-month, randomised controlled 2-cohort parallel group intervention trial, with initial assessment at baseline and repeated every three months. A sample of 166 healthy Australian men and women aged 65 years and above, with normal cognitive function and proficient in English language were recruited from metropolitan Adelaide, South Australia for the study. Participants randomly allocated to the experimental group are required to maintain an intervention dietary pattern based from the traditional Cretan MedDiet (i.e. vegetables, fruits, olive oil, legumes, fish, whole grain cereals, nuts and seeds and low consumption of processed foods, dairy products, red meat and vegetable oils) for six months, while those participants allocated to the control group are asked to maintain their customary lifestyle and diet. The primary outcome of interest is the quantitative difference in age-related cognitive performance, as measured by latent variables (cognitive constructs) sensitive to normal ageing and diet (i.e. speed of processing, memory, attention, executive functions, visual spatial and visuomotor ability). Secondary outcomes include change in biomarkers of inflammation, oxidative stress, lipid metabolism, glucose, insulin, blood flow velocity, and psychological well-being factors (i.e. stress, sleep, anxiety, depression). DISCUSSION To our knowledge this will be one of the first randomised clinical trials worldwide to provide evidence for the cause-effect relationship between the MedDiet and age-related cognitive function in a healthy older adult population (≥65 years and over). TRIAL REGISTRATION Australia and New Zealand Clinical Trials Register (ANZCTR): ACTRN12613000602729.
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Favourable effects of consuming a Palaeolithic-type diet on characteristics of the metabolic syndrome: a randomized controlled pilot-study.
Boers, I, Muskiet, FA, Berkelaar, E, Schut, E, Penders, R, Hoenderdos, K, Wichers, HJ, Jong, MC
Lipids in health and disease. 2014;13:160
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The prevalence of metabolic syndrome (MetS) is increasing rapidly worldwide and is a major risk factor for type 2 diabetes (DM2) and cardiovascular disease (CVD). Modern lifestyle-induced insulin resistance and chronic systemic low grade inflammation are considered at the root of the MetS. Therefore, dietary patterns of our Palaeolithic ancestors may be ideal for prevention and treatment of metabolic disorders since they are thought to be in line with the evolution of human physiology and metabolism. The aim of this randomized controlled pilot study was to assess the efficacy of a Palaeolithic-type diet in improving the characteristics of MetS, compared to a diet based on healthy eating guidelines. The study included 34 participants with MetS who consumed their allocated diets for two weeks. Efforts were made to prevent weight loss so that any favourable effects could be explained by the dietary intervention and not by the positive health effects of weight loss. The findings of this study showed that the Palaeolithic-type diet significantly lowered blood pressure, total cholesterol and triglycerides, as well as improved HDL-cholesterol, compared to the reference diet. The participants in the Palaeolithic diet intervention also had fewer characteristics of MetS and a tendency to higher insulin sensitivity at the end of the study. Despite efforts to keep body-weight stable, more weight was lost by the participants in the Palaeolithic group. No changes were observed in the secondary outcomes of inflammation, intestinal permeability and salivary cortisol, which the authors explain by the short duration of the intervention and the attempt to prevent weight loss. The authors conclude that future studies should take full additional advantage of the greater weight loss with the Palaeolithic diet, which may be more satiating than other diets, hence allowing weight loss to happen.
Abstract
BACKGROUND The main goal of this randomized controlled single-blinded pilot study was to study whether, independent of weight loss, a Palaeolithic-type diet alters characteristics of the metabolic syndrome. Next we searched for outcome variables that might become favourably influenced by a Paleolithic-type diet and may provide new insights in the pathophysiological mechanisms underlying the metabolic syndrome. In addition, more information on feasibility and designing an innovative dietary research program on the basis of a Palaeolithic-type diet was obtained. METHODS Thirty-four subjects, with at least two characteristics of the metabolic syndrome, were randomized to a two weeks Palaeolithic-type diet (n = 18) or an isoenergetic healthy reference diet, based on the guidelines of the Dutch Health Council (n = 14). Thirty-two subjects completed the study. Measures were taken to keep bodyweight stable. As primary outcomes oral glucose tolerance and characteristics of the metabolic syndrome (abdominal circumference, blood pressure, glucose, lipids) were measured. Secondary outcomes were intestinal permeability, inflammation and salivary cortisol. Data were collected at baseline and after the intervention. RESULTS Subjects were 53.5 (SD9.7) year old men (n = 9) and women (n = 25) with mean BMI of 31.8 (SD5.7) kg/m2. The Palaeolithic-type diet resulted in lower systolic blood pressure (-9.1 mmHg; P = 0.015), diastolic blood pressure (-5.2 mmHg; P = 0.038), total cholesterol (-0.52 mmol/l; P = 0.037), triglycerides (-0.89 mmol/l; P = 0.001) and higher HDL-cholesterol (+0.15 mmol/l; P = 0.013), compared to reference. The number of characteristics of the metabolic syndrome decreased with 1.07 (P = 0.010) upon the Palaeolithic-type diet, compared to reference. Despite efforts to keep bodyweight stable, it decreased in the Palaeolithic group compared to reference (-1.32 kg; P = 0.012). However, favourable effects remained after post-hoc adjustments for this unintended weight loss. No changes were observed for intestinal permeability, inflammation and salivary cortisol. CONCLUSIONS We conclude that consuming a Palaeolithic-type diet for two weeks improved several cardiovascular risk factors compared to a healthy reference diet in subjects with the metabolic syndrome. TRIAL REGISTRATION Nederlands Trial Register NTR3002.