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Reducing meat and/or dairy consumption in adults: a systematic review and meta-analysis of effects on protein intake, anthropometric values, and body composition.
Habumugisha, T, Engebretsen, IMS, Måren, IE, Kaiser, CWM, Dierkes, J
Nutrition reviews. 2024;82(3):277-301
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Reduced consumption of meat and dairy is being encouraged over climate change fears, and health implications. However, meat and dairy provide high quality protein and nutrients and concerns have grown over nutrient deficiencies in people on plant-based diets. This systematic review and meta-analysis of 19 randomised control trials (RCTs) aimed to determine the effect of a reduced meat/dairy diet in protein intake, and body shape and composition. The results showed that the RCTs included ran for a median duration of 12 weeks. Participants on a reduced meat/dairy diet had lower protein intakes, and reduced meat/dairy diet had no effect on body weight, body mass index, waist circumference, body fat, or muscle mass. It was concluded that a low meat/dairy diet decreases protein intake, however it does not affect body shape, or composition. It was also concluded that studies of longer duration are warranted to determine long-term effects. This study could be used by healthcare professionals to understand that reduced meat/dairy intake over a moderate period of time may have no effect on body shape or composition but will result in lower protein intakes.
Abstract
CONTEXT Consumers are increasingly encouraged to reduce meat and dairy consumption. However, few meta-analyses of randomized controlled trials (RCTs) on the effect of reducing meat and/or dairy on (absolute) protein intake, anthropometric values, and body composition are available. OBJECTIVE The aim of this systematic review and meta-analysis was to evaluate the effect of reducing meat and/or dairy consumption on (absolute) protein intake, anthropometric values, and body composition in adults aged ≥ 45 years. DATA SOURCES The MEDLINE, Cochrane CENTRAL, Embase, ClinicalTrials.gov, and International Clinical Trials Registry Platform databases were searched up to November 24, 2021. DATA EXTRACTION Randomized controlled trials reporting protein intake, anthropometric values, and body composition were included. DATA ANALYSIS Data were pooled using random-effects models and expressed as the mean difference (MD) with 95%CI. Heterogeneity was assessed and quantified using Cochran's Q and I2 statistics. In total, 19 RCTs with a median duration of 12 weeks (range, 4-24 weeks) and a total enrollment of 1475 participants were included. Participants who consumed meat- and/or dairy-reduced diets had a significantly lower protein intake than those who consumed control diets (9 RCTs; MD, -14 g/d; 95%CI, -20 to -8; I2 = 81%). Reducing meat and/or dairy consumption had no significant effect on body weight (14 RCTs; MD, -1.2 kg; 95%CI, -3 to 0.7; I2 = 12%), body mass index (13 RCTs; MD, -0.3 kg/m2; 95%CI, -1 to 0.4; I2 = 34%), waist circumference (9 RCTs; MD, -0.5 cm; 95%CI, -2.1 to 1.1; I2 = 26%), amount of body fat (8 RCTs; MD, -1.0 kg; 95%CI, -3.0 to 1.0; I2 = 48%), or lean body mass (9 RCTs; MD, -0.4 kg; 95%CI, -1.5 to 0.7; I2 = 0%). CONCLUSION Reduction of meat and/or dairy appears to reduce protein intake. There is no evidence of a significant impact on anthropometric values or body composition. More long-term intervention studies with defined amounts of meat and dairy are needed to investigate the long-term effects on nutrient intakes and health outcomes. SYSTEMATIC REVIEW REGISTRATION PROSPERO registration no. CRD42020207325.
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Impact of α-Linolenic Acid, the Vegetable ω-3 Fatty Acid, on Cardiovascular Disease and Cognition.
Sala-Vila, A, Fleming, J, Kris-Etherton, P, Ros, E
Advances in nutrition (Bethesda, Md.). 2022;13(5):1584-1602
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α-Linolenic acid (ALA) is an omega-3 fatty acid found in seeds and nuts such as flaxseeds, chia seeds, and walnuts and in oils such as canola oil, soybean oil, flaxseed oil and walnut oil. It has been shown to reduce the risk of coronary heart disease and cardiovascular disease. This meta-analysis examined the results of various studies, including epidemiologic studies, randomized controlled trials, and systematic reviews, to evaluate the beneficial effects of ALA in improving cognitive function and reducing the risk of cardiovascular disease and coronary heart disease. The included studies showed a correlation between ALA intake and a decreased risk of cardiovascular disease and coronary heart disease, possibly due to ALA's anti-inflammatory properties, as well as its ability to reduce total cholesterol, LDL cholesterol, triglycerides, and blood pressure. The analysis also found that ALA intake may reduce the risk of type 2 diabetes and cognitive impairment. Healthcare professionals can leverage the findings of this analysis to educate individuals about the benefits of dietary ALA in improving cardiovascular and cognitive outcomes. However, further studies are necessary to establish definitive conclusions and determine therapeutic dosage.
Abstract
Given the evidence of the health benefits of plant-based diets and long-chain n-3 (ω-3) fatty acids, there is keen interest in better understanding the role of α-linolenic acid (ALA), a plant-derived n-3 fatty acid, on cardiometabolic diseases and cognition. There is increasing evidence for ALA largely based on its major food sources (i.e., walnuts and flaxseed); however, this lags behind our understanding of long-chain n-3 fatty acids. Meta-analyses of observational studies have shown that increasing dietary ALA is associated with a 10% lower risk of total cardiovascular disease and a 20% reduced risk of fatal coronary heart disease. Three randomized controlled trials (RCTs) [AlphaOmega trial, Prevención con Dieta Mediterránea (PREDIMED) trial, and Lyon Diet Heart Study] all showed benefits of diets high in ALA on cardiovascular-related outcomes, but the AlphaOmega trial, designed to specifically evaluate ALA effects, only showed a trend for benefit. RCTs have shown that dietary ALA reduced total cholesterol, LDL cholesterol, triglycerides, and blood pressure, and epidemiologic studies and some trials also have shown an anti-inflammatory effect of ALA, which collectively account for, in part, the cardiovascular benefits of ALA. A meta-analysis reported a trend toward diabetes risk reduction with both dietary and biomarker ALA. For metabolic syndrome and obesity, the evidence for ALA benefits is inconclusive. The role of ALA in cognition is in the early stages but shows promising evidence of counteracting cognitive impairment. Much has been learned about the health benefits of ALA and with additional research we will be better positioned to make strong evidence-based dietary recommendations for the reduction of many chronic diseases.
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Adherence to Mediterranean Diet and NAFLD in Patients with Metabolic Syndrome: The FLIPAN Study.
Montemayor, S, Mascaró, CM, Ugarriza, L, Casares, M, Llompart, I, Abete, I, Zulet, MÁ, Martínez, JA, Tur, JA, Bouzas, C
Nutrients. 2022;14(15)
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Non-alcoholic fatty liver disease (NAFLD) is characterised by fat deposition that is not linked to excessive alcohol intake. This condition is often linked to other health issues such as obesity, metabolic syndrome, type 2 diabetes and cardiovascular disease, and they share common diagnostic biomarkers. An unhealthy diet and lifestyle are also linked to the progression of NAFLD. Mediterranean diet is a predominantly plant-based diet that may have an association with lower risk and reduced severity of NAFLD. This multicentre, prospective, randomised controlled trial included one hundred and thirty-six NAFLD patients to analyse the effect of Mediterranean diet adherence on NAFLD in patients with metabolic syndrome. The NAFLD patients followed a personalised Mediterranean diet and physical activity interventions for six months. Individuals with greater adherence to the Mediterranean diet and physical activity interventions showed improvements in body mass index, body weight, waist circumference, blood pressure and intrahepatic fat content after six months of intervention. Healthcare professionals can use the results of this study to understand the benefits of adherence to the Mediterranean diet and physical activity interventions in reducing NAFLD severity and metabolic irregularities. However, due to the small sample size of this study, further robust studies are required to evaluate the benefits of different dietary strategies, the therapeutic value of different food items and the intervention duration required to achieve improvements in NAFLD and metabolic syndrome.
Abstract
Unhealthy diet is an important factor in the progression of non-alcoholic fatty liver disease (NAFLD). Previous studies showed the benefits of a Mediterranean diet (MedDiet) on Metabolic syndrome (MetS), type 2 diabetes mellitus (T2DM), and cardiovascular diseases, which usually have a pathophysiological relationship with NAFLD. To assess the effect of adherence to a MedDiet on NAFLD in MetS patients after lifestyle intervention, this multicentre (Mallorca and Navarra, Spain) prospective randomized trial, with personalized nutritional intervention based on a customized MedDiet, coupled with physical activity promotion was performed to prevent, and reverse NAFLD among patients with MetS. The current analysis included 138 patients aged 40 to 60 years old, Body Mass Index (BMI) 27-40 kg/m2, diagnosed with NAFLD using MRI, and MetS according to the International Diabetes Federation (IDF). A validated food frequency questionnaire was used to assess dietary intake. Adherence to Mediterranean diet by means of a 17-item validated questionnaire, anthropometrics, physical activity, blood pressure, blood biochemical parameters, and intrahepatic fat contents (IFC) were measured. The independent variable used was changes in MedDiet adherence, categorized in tertiles after 6 months follow-up. Subjects with high adherence to the MedDiet showed higher decreases in BMI, body weight, WC, SBP, DBP, and IFC. An association between improvement in adherence to the MedDiet and amelioration of IFC after 6-month follow-up was observed. High adherence to the MedDiet is associated with better status of MetS features, and better values of IFC.
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Effects of Plant-Based Diets on Weight Status: A Systematic Review.
Tran, E, Dale, HF, Jensen, C, Lied, GA
Diabetes, metabolic syndrome and obesity : targets and therapy. 2020;13:3433-3448
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Being overweight or obese is a huge risk factor for many detrimental conditions. It is estimated that around one-third of the world’s population will be overweight or obese by 2025. Hence there is a need to look at dietary strategies in the prevention and treatment of overweight and obesity. Plant-based diets have always existed, however interest in the topic has increased recently and more research is being done on the health-related effects of different plant-based diets. There are many reasons why someone might convert to a plant-based diet, possible health benefits such as weight management are among the most common. The purpose of this review was to evaluate intervention studies assessing the effects of different plant-based diets on body mass index and weight. The results suggest that plant-based diets may improve weight status in some patient groups. It should be noted that only one study out of the 19 included in the review had normal weight, clinically healthy participants. The study populations for the rest were overweight, obese or had type 2 diabetes. Future research should aim to include a representative study population and apply study diets without dietary restrictions.
Abstract
There is an increasing number of people who convert to a plant-based diet. The desire for health benefits, including weight management, is often a contributing factor behind this dietary choice. The purpose of this review was to evaluate intervention studies assessing the effects of different plant-based diets on body mass index and weight. A literature search was conducted in PubMed until December 2019. Twenty-two publications from 19 studies were included. The majority of them were randomized controlled trials comparing a low-fat vegan diet to an omnivore diet in participants with overweight, type 2 diabetes mellitus and/or cardiovascular disease. All studies reported weight reductions, of which seven revealed significant differences, and four revealed non-significant differences between the intervention and the control groups. The results suggest that plant-based diets may improve weight status in some patient groups. Due to restrictions in fat intake in many studies, followed by reduced energy intake, the effects of the different interventions differ depending on the specific plant-based diets investigated. Future research should aim to include a representative study population and apply study diets without dietary restrictions.
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Health Biomarkers in Adults Are More Closely Linked to Diet Quality Attributes Than to Plant-Based Diet Categorization.
Mayra, S, Ugarte, N, Johnston, CS
Nutrients. 2019;11(6)
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Plant-based diets rich in fruits, vegetables, whole grains, nuts, and legumes are consistently linked to reduced risk for chronic disease, improved cognition, and longevity. The aim of the study was to examine the diet quality and blood metabolites of vegetarian and omnivore adults to determine adherence to plant-based diets compared to high-quality eating patterns. The study is a cross-sectional investigation. Thirty-three participants (17 vegetarians: 3 men/14 women; 16 omnivores: 3 men/13 women) aged between 18 and 65 years were enrolled for the study. Results indicate the health biomarkers did not differ between vegetarians and omnivores matched for gender, age, and adiposity. However, when participants were regrouped by low-quality versus high-quality diets, data suggests that several common health biomarkers are more closely aligned with diet quality attributes than with plant-based diet categorisation. Authors conclude that healthcare practitioners should emphasize diet quality in their messages to their clients and discuss the importance of eating whole, minimally processed foods with less added fat and sugars.
Abstract
Although plant-based diets are promoted for healthy outcomes, these diets are not synonymous with high-quality diets. Plant-based diets can include highly processed, less healthful foods, including savory snacks, pastries, and sugary fruit drinks. This cross-sectional study examined the diet quality of vegetarian and omnivorous adults, matched for gender, age, and adiposity, and related diet quality to standard health biomarkers. Diet quality was assessed using the Rapid Eating and Activity Assessment for Participants Short Version questionnaire. Participants (17 vegetarians and 16 omnivores; 28.2 ± 8.9 years; 22.5 ± 2.7 kg/m2) were non-smokers and healthy by self-report. The median duration of adherence to the vegetarian diet was 27 months. Physical activity level and diet quality did not differ significantly between diet groups. Moreover, health biomarkers did not differ by diet groups. When participants were regrouped by low versus high diet quality, health biomarkers differed significantly between groups for fasting insulin, HOMA-IR, triglyceride (TG)/HDL ratio, and blood folate, with more favorable levels in the group with high diet quality. These data suggest that health biomarkers more closely align with diet quality attributes than with plant-based diet categorization. Thus, messaging focused on healthy diet attributes may lead to better health outcomes than the simple promotion of plant-based diets.
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A Plant-Based High-Carbohydrate, Low-Fat Diet in Overweight Individuals in a 16-Week Randomized Clinical Trial: The Role of Carbohydrates.
Kahleova, H, Dort, S, Holubkov, R, Barnard, ND
Nutrients. 2018;10(9)
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The prevalence of obesity has reached epidemic proportions. As a result, the risk of obesity-related diseases is rapidly increasing, and increased body weight is associated with a higher all-cause mortality. The aim of the study is to determine whether high carbohydrate and fibre intakes in the context of a plant-based diet are associated with weight loss, reduction in fat mass, and decrease in insulin resistance. The study is a single-centre, randomised controlled study. The participants recruited for the study were adults with a BMI between 28 and 40 kg/m2. Results demonstrated that increased consumption of carbohydrates and dietary fibre, as part of a plant-based high-carbohydrate, low-fat diet, was associated with reduced body weight, fat mass, and insulin resistance in overweight individuals. Authors conclude that increased consumption of total carbohydrates and total fibre, particularly insoluble fibre, was linked with lower body mass index and volume in visceral fat. Furthermore, increased fibre intake is also associated with decrease in fat mass.
Abstract
The effects of carbohydrates on body weight and insulin sensitivity are controversial. In this 16-week randomized clinical trial, we tested the role of a low-fat, plant-based diet on body weight, body composition and insulin resistance. As a part of this trial, we investigated the role of changes in carbohydrate intake on body composition and insulin resistance. Participants (n = 75) were randomized to follow a plant-based high-carbohydrate, low-fat (vegan) diet (n = 38) or to maintain their current diet (n = 37). Dual-energy X-ray absorptiometry was used to measure body composition. Insulin resistance was assessed with the Homeostasis Model Assessment (HOMA-IR) index. A repeated measure ANOVA model was used to test the between-group differences from baseline to 16 weeks. A linear regression model was used to test the relationship between carbohydrate intake, and body composition and insulin resistance. Weight decreased significantly in the vegan group (treatment effect -6.5 [95% CI -8.9 to -4.1] kg; Gxt, p < 0.001). Fat mass was reduced in the vegan group (treatment effect -4.3 [95% CI -5.4 to -3.2] kg; Gxt, p < 0.001). HOMA-IR was reduced significantly in the vegan group (treatment effect -1.0 [95% CI -1.2 to -0.8]; Gxt, p = 0.004). Changes in consumption of carbohydrate, as a percentage of energy, correlated negatively with changes in BMI (r = -0.53, p < 0.001), fat mass (r = -0.55, p < 0.001), volume of visceral fat (r = -0.35, p = 0.006), and HOMA (r = -0.27, p = 0.04). These associations remained significant after adjustment for energy intake. Changes in consumption of total and insoluble fiber correlated negatively with changes in BMI (r = -0.43, p < 0.001; and r = -0.46, p < 0.001, respectively), fat mass (r = -0.42, p < 0.001; and r = -0.46, p < 0.001, respectively), and volume of visceral fat (r = -0.29, p = 0.03; and r = -0.32, p = 0.01, respectively). The associations between total and insoluble fiber and changes in BMI and fat mass remained significant even after adjustment for energy intake. Increased carbohydrate and fiber intake, as part of a plant-based high-carbohydrate, low-fat diet, are associated with beneficial effects on weight, body composition, and insulin resistance.