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Cardiovascular Diagnosis and Therapy Oct 2014Previous studies have suggested an association between vegetarian diets and improvements in glycemic control in diabetes, although this relationship is not well...
INTRODUCTION
Previous studies have suggested an association between vegetarian diets and improvements in glycemic control in diabetes, although this relationship is not well established. No meta-analysis of these studies has been performed.
METHODS
To conduct a systematic review and meta-analysis of controlled clinical trials examining the association between vegetarian diets and glycemic control in type 2 diabetes.
DATA SOURCE
The electronic databases Medline, Web of Science, Excerpta Medica Database (EMBASE), and Cochrane Central Register of Controlled Trials were searched for articles published in any language through December 9, 2013.
STUDY SELECTION
The following criteria were used for study inclusion: (I) age of participants >20 years; (II) vegetarian diet as intervention; (III) mean difference in hemoglobin A1c (HbA1c) and/or fasting blood glucose levels used as outcomes; and (IV) controlled trials, duration ≥4 weeks. Exclusion criteria were: (I) not an original investigation; (II) duplicate samples; (III) diabetes other than type 2; (IV) multiple interventions; and (V) uncontrolled studies.
DATA EXTRACTION AND SYNTHESIS
The data collected included study design, baseline population characteristics, dietary data, and outcomes. Data were pooled using a random-effects model.
MAIN OUTCOMES AND MEASURES
Differences in HbA1c and fasting blood glucose levels associated with vegetarian diets were assessed.
RESULTS
Of 477 studies identified, six met the inclusion criteria (n=255, mean age 42.5 years). Consumption of vegetarian diets was associated with a significant reduction in HbA1c [-0.39 percentage point; 95% confidence interval (CI), -0.62 to -0.15; P=0.001; I(2)=3.0; P for heterogeneity =0.389], and a non-significant reduction in fasting blood glucose concentration (-0.36 mmol/L; 95% CI, -1.04 to 0.32; P=0.301; I(2)=0; P for heterogeneity =0.710), compared with consumption of comparator diets.
CONCLUSIONS
Consumption of vegetarian diets is associated with improved glycemic control in type 2 diabetes. PROSPERO registration number is CRD42013004370.
PubMed: 25414824
DOI: 10.3978/j.issn.2223-3652.2014.10.04 -
Critical Reviews in Food Science and... 2022We aimed to examine the association between adherence to plant-based diets (PBDs) and the risk of mortality among the general population. Relevant investigations were... (Meta-Analysis)
Meta-Analysis
We aimed to examine the association between adherence to plant-based diets (PBDs) and the risk of mortality among the general population. Relevant investigations were identified through PubMed, Scopus, Embase, and ISI Web of Knowledge. Data were pooled using a random-effects or a fixed-effects model. Twelve prospective cohort studies with 42,697 deaths among 508,861 participants were included. The hazard ratios (HRs) for the highest compared to the lowest category of adherence to the PBDs were 0.90 (95% confidence interval [CI]: 0.82, 0.99; I = 91%, n = 12) for all-cause and 0.77 (95% CI: 0.70, 0.86; I = 36%, n = 8) for coronary heart disease (CHD) mortality. Among PBDs subtypes, there was an inverse association between healthy plant-based 0.92 (95% CI: 0.88, 0.96; I = 0%, n = 2), Pesco-vegetarian 0.81 (95% CI: 0.70, 0.92; I = 0%, n = 2), and Pro-vegetarian 0.74 (95% CI: 0.55, 0.88; I = 61.2%, n = 2) diets and the risk of all-cause mortality. A vegetarian diet was also associated with lower risk of mortality due to cardiovascular 0.92 (95% CI: 0.85, 0.99; I = 0%, n = 5) and CHD 0.76 (95% CI: 0.68, 0.85; I = 35%, n = 7). Our findings show the potential protective role of PBDs against chronic disease mortality. As there were certain limitations in some of the studies included in this systematic review and meta-analysis, further research is necessary to confirm our findings.
Topics: Cardiovascular Diseases; Cohort Studies; Diet; Diet, Vegetarian; Humans; Prospective Studies; Vegetarians
PubMed: 33951994
DOI: 10.1080/10408398.2021.1918628 -
Journal of the American Dietetic... May 2010This systematic review assesses the effectiveness and safety of dietary interventions for rheumatoid arthritis. Randomized controlled trials comparing any dietary... (Review)
Review
This systematic review assesses the effectiveness and safety of dietary interventions for rheumatoid arthritis. Randomized controlled trials comparing any dietary manipulation with an ordinary diet were included. Eight randomized controlled trials with a total of 366 patients were included. One trial found that fasting, followed by 13 months on a vegetarian eating plan, might reduce pain (mean difference on a zero to 10 scale -1.89, 95% confidence interval [CI] -3.62 to -0.16). Another single trial found that a 12-week Cretan Mediterranean eating plan might reduce pain (mean difference on a 0 to 100 scale -14.00, 95% CI -23.6 to -4.37). Due to inadequate data reporting, the effects of vegan eating plans and elimination diets are uncertain. When comparing any dietary manipulation with an ordinary diet we found a higher total drop-out of 8% (risk difference 0.08, 95% CI -0.01 to 0.17), higher treatment-related drop-out of 5% (risk difference 0.05, 95% CI -0.03 to 0.14) and a significantly higher weight loss (weighted mean difference -3.24, 95% CI -4.81 to -1.67 kg) in the diet groups compared to the control groups. The effects of dietary manipulation, including vegetarian, Mediterranean, and elemental eating plans, and elimination diets on rheumatoid arthritis are still uncertain due to the included studies being small, single trials with moderate to high risk of bias. We conclude that higher dropout rates and weight loss in the groups with dietary manipulation indicate that potential adverse effects should not be ignored.
Topics: Arthralgia; Arthritis, Rheumatoid; Diet, Mediterranean; Diet, Vegetarian; Fasting; Female; Humans; Male; Middle Aged; Patient Compliance; Randomized Controlled Trials as Topic; Treatment Outcome; Weight Loss
PubMed: 20430134
DOI: 10.1016/j.jada.2010.02.010 -
The British Journal of Nutrition Mar 2013There is strong evidence indicating that elevated plasma total homocysteine (tHcy) levels are a major independent biomarker and/or a contributor to chronic conditions,... (Comparative Study)
Comparative Study Meta-Analysis Review
There is strong evidence indicating that elevated plasma total homocysteine (tHcy) levels are a major independent biomarker and/or a contributor to chronic conditions, such as CVD. A deficiency of vitamin B₁₂ can elevate homocysteine. Vegetarians are a group of the population who are potentially at greater risk of vitamin B₁₂ deficiency than omnivores. This is the first systematic review and meta-analysis to appraise a range of studies that compared the homocysteine and vitamin B₁₂ levels of vegetarians and omnivores. The search methods employed identified 443 entries, from which, by screening using set inclusion and exclusion criteria, six eligible cohort case studies and eleven cross-sectional studies from 1999 to 2010 were revealed, which compared concentrations of plasma tHcy and serum vitamin B₁₂ of omnivores, lactovegetarians or lacto-ovovegetarians and vegans. Of the identified seventeen studies (3230 participants), only two studies reported that vegan concentrations of plasma tHcy and serum vitamin B₁₂ did not differ from omnivores. The present study confirmed that an inverse relationship exists between plasma tHcy and serum vitamin B₁₂, from which it can be concluded that the usual dietary source of vitamin B₁₂ is animal products and those who choose to omit or restrict these products are destined to become vitamin B₁₂ deficient. At present, the available supplement, which is usually used for fortification of food, is the unreliable cyanocobalamin. A well-designed study is needed to investigate a reliable and suitable supplement to normalise the elevated plasma tHcy of a high majority of vegetarians. This would fill the gaps in the present nutritional scientific knowledge.
Topics: Adult; Cohort Studies; Cross-Sectional Studies; Diet; Diet, Vegetarian; Dietary Supplements; Female; Homocysteine; Humans; Hyperhomocysteinemia; Male; Middle Aged; Vitamin B 12; Vitamin B 12 Deficiency
PubMed: 23298782
DOI: 10.1017/S000711451200520X -
Advances in Nutrition (Bethesda, Md.) Feb 2022Altered immune cell phenotype and chronic inflammation are key features shared by various chronic diseases. Evidence from nutritional interventions aimed at alleviating... (Meta-Analysis)
Meta-Analysis
Altered immune cell phenotype and chronic inflammation are key features shared by various chronic diseases. Evidence from nutritional interventions aimed at alleviating inflammation could be a promising approach for the prevention of adverse health outcomes. We therefore aimed to conduct a systematic review and meta-analysis of randomized controlled trials (RCTs) to summarize the recent evidence on the effects of dietary patterns on inflammatory and immune-related biomarkers in humans. PubMed, Medline, and Web of Science databases were searched for publications up to October 2020. In total, 22 RCTs were included in the meta-analysis conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The Mediterranean diet appeared as the dietary pattern that showed the most prominent reductions of inflammatory biomarkers such as IL-6 [mean difference (MD): -1.07 pg/mL (95% CI: -1.94, -0.20); I2: 96%], IL-1β [MD: -0.46 pg/mL (95% CI: -0.66, -0.25); I2: 0%], and C-reactive protein [MD: -1.00 mg/L (95% CI: -2.02, 0.01); I2: 100%]. No substantial effects were observed for the additional dietary patterns studied in intervention research, including the Dietary Adherence to Stop Hypertension diet, and the vegetarian or vegan diets. Future large-scale multifactorial intervention studies are warranted to allow direct comparison of various dietary patterns in relation to a range of biomarkers reflecting multiple inflammatory and immune-related pathways.
Topics: Biomarkers; Diet, Mediterranean; Humans; Immunity; Inflammation; Randomized Controlled Trials as Topic
PubMed: 34607347
DOI: 10.1093/advances/nmab086 -
Journal of the Academy of Nutrition and... Jun 2015In observational studies, vegetarians generally have lower body weights compared with omnivores. However, weight changes that occur when vegetarian diets are prescribed... (Meta-Analysis)
Meta-Analysis Review
In observational studies, vegetarians generally have lower body weights compared with omnivores. However, weight changes that occur when vegetarian diets are prescribed have not been well quantified. We estimated the effect on body weight when vegetarian diets are prescribed. We searched PubMed, EMBASE, and the Cochrane Central Register of Controlled Trials for articles through December 31, 2013. Additional articles were identified from reference lists. We included intervention trials in which participants were adults, interventions included vegetarian diets of ≥4 weeks' duration without energy intake limitations, and effects on body weight were reported. Two investigators independently extracted data using predetermined fields. Estimates of body weight change, comparing intervention groups to untreated control groups, were derived using a random effects model to estimate the weighted mean difference. To quantify effects on body weight of baseline weight, sex, age, study duration, study goals, type of diet, and study authorship, additional analyses examined within-group changes for all studies reporting variance data. We identified 15 trials (17 intervention groups), of which 4 included untreated controls. Prescription of vegetarian diets was associated with a mean weight change of -3.4 kg (95% CI -4.4 to -2.4; P<0.001) in an intention-to-treat analysis and -4.6 kg (95% CI -5.4 to -3.8; P<0.001) in a completer analysis (omitting missing post-intervention values). Greater weight loss was reported in studies with higher baseline weights, smaller proportions of female participants, older participants, or longer durations, and in studies in which weight loss was a goal. Using baseline data for missing values, I(2) equaled 52.3 (P=0.10), indicating moderate heterogeneity. When missing data were omitted, I(2) equaled 0 (P=0.65), indicating low heterogeneity. Studies are relatively few, with variable quality. The prescription of vegetarian diets reduces mean body weight, suggesting potential value for prevention and management of weight-related conditions.
Topics: Body Weight; Databases, Factual; Diet; Diet, Vegetarian; Energy Intake; Humans; Motor Activity; Non-Randomized Controlled Trials as Topic; Randomized Controlled Trials as Topic
PubMed: 25620754
DOI: 10.1016/j.jand.2014.11.016 -
Nutrients May 2020Vegan and vegetarian diets are becoming increasingly popular. Dietary restrictions may increase the risk of iodine deficiency. This systematic review aims to assess...
Vegan and vegetarian diets are becoming increasingly popular. Dietary restrictions may increase the risk of iodine deficiency. This systematic review aims to assess iodine intake and status in adults following a vegan or vegetarian diet in industrialised countries. A systematic review and quality assessment were conducted in the period May 2019-April 2020 according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Studies were identified in Ovid MEDLINE, Embase, Web of Science, PubMed, Scopus, and secondary sources. Fifteen articles met inclusion criteria. Participants included 127,094 adults (aged ≥ 18 years). Vegan groups presented the lowest median urinary iodine concentrations, followed by vegetarians, and did not achieve optimal status. The highest iodine intakes were recorded in female vegans (1448.0 ± 3879.0 µg day) and the lowest in vegetarians (15.6 ± 21.0 µg day). Omnivores recorded the greatest intake in 83% of studies. Seaweed contributed largely to diets of vegans with excessive iodine intake. Vegans appear to have increased risk of low iodine status, deficiency and inadequate intake compared with adults following less restrictive diets. Adults following vegan and vegetarian diets living in countries with a high prevalence of deficiency may be more vulnerable. Therefore, further monitoring of iodine status in industrialised countries and research into improving the iodine intake and status of adults following vegan and vegetarian diets is required.
Topics: Adolescent; Adult; Diet, Vegan; Eating; Female; Humans; Iodine; Male; Middle Aged; Nutritional Physiological Phenomena; Nutritional Status; Risk; Seaweed; Vegans; Vegetarians; Young Adult
PubMed: 32486114
DOI: 10.3390/nu12061606 -
The Cochrane Database of Systematic... Feb 2021Diet plays a major role in the aetiology of cardiovascular disease (CVD) and as a modifiable risk factor is the focus of many prevention strategies. Recently vegan diets... (Meta-Analysis)
Meta-Analysis
BACKGROUND
Diet plays a major role in the aetiology of cardiovascular disease (CVD) and as a modifiable risk factor is the focus of many prevention strategies. Recently vegan diets have gained popularity and there is a need to synthesise existing clinical trial evidence for their potential in CVD prevention.
OBJECTIVES
To determine the effectiveness of following a vegan dietary pattern for the primary and secondary prevention of CVD.
SEARCH METHODS
We searched the following electronic databases on 4 February 2020: the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase and Web of Science Core Collection. We also searched ClinicalTrials.gov in January 2021. We applied no language restrictions.
SELECTION CRITERIA
We selected randomised controlled trials (RCTs) in healthy adults and adults at high risk of CVD (primary prevention) and those with established CVD (secondary prevention). A vegan dietary pattern excludes meat, fish, eggs, dairy and honey; the intervention could be dietary advice, provision of relevant foods, or both. The comparison group received either no intervention, minimal intervention, or another dietary intervention. Outcomes included clinical events and CVD risk factors. We included only studies with follow-up periods of 12 weeks or more, defined as the intervention period plus post-intervention follow-up.
DATA COLLECTION AND ANALYSIS
Two review authors independently assessed studies for inclusion, extracted data and assessed risks of bias. We used GRADE to assess the certainty of the evidence. We conducted three main comparisons: 1. Vegan dietary intervention versus no intervention or minimal intervention for primary prevention; 2. Vegan dietary intervention versus another dietary intervention for primary prevention; 3. Vegan dietary intervention versus another dietary intervention for secondary prevention.
MAIN RESULTS
Thirteen RCTs (38 papers, 7 trial registrations) and eight ongoing trials met our inclusion criteria. Most trials contributed to primary prevention: comparisons 1 (four trials, 466 participants randomised) and comparison 2 (eight trials, 409 participants randomised). We included only one secondary prevention trial for comparison 3 (63 participants randomised). None of the trials reported on clinical endpoints. Other primary outcomes included lipid levels and blood pressure. For comparison 1 there was moderate-certainty evidence from four trials with 449 participants that a vegan diet probably led to a small reduction in total cholesterol (mean difference (MD) -0.24 mmol/L, 95% confidence interval (CI) -0.36 to -0.12) and low-density lipoprotein (LDL) cholesterol (MD -0.22 mmol/L, 95% CI -0.32 to -0.11), a very small decrease in high-density lipoprotein (HDL) levels (MD -0.08 mmol/L, 95% CI -0.11 to -0.04) and a very small increase in triglyceride levels (MD 0.11 mmol/L, 95% CI 0.01 to 0.21). The very small changes in HDL and triglyceride levels are in the opposite direction to that expected. There was a lack of evidence for an effect with the vegan dietary intervention on systolic blood pressure (MD 0.94 mmHg, 95% CI -1.18 to 3.06; 3 trials, 374 participants) and diastolic blood pressure (MD -0.27 mmHg, 95% CI -1.67 to 1.12; 3 trials, 372 participants) (low-certainty evidence). For comparison 2 there was a lack of evidence for an effect of the vegan dietary intervention on total cholesterol levels (MD -0.04 mmol/L, 95% CI -0.28 to 0.20; 4 trials, 163 participants; low-certainty evidence). There was probably little or no effect of the vegan dietary intervention on LDL (MD -0.05 mmol/L, 95% CI -0.21 to 0.11; 4 trials, 244 participants) or HDL cholesterol levels (MD -0.01 mmol/L, 95% CI -0.08 to 0.05; 5 trials, 256 participants) or triglycerides (MD 0.21 mmol/L, 95% CI -0.07 to 0.49; 5 trials, 256 participants) compared to other dietary interventions (moderate-certainty evidence). We are very uncertain about any effect of the vegan dietary intervention on systolic blood pressure (MD 0.02 mmHg, 95% CI -3.59 to 3.62) or diastolic blood pressure (MD 0.63 mmHg, 95% CI -1.54 to 2.80; 5 trials, 247 participants (very low-certainty evidence)). Only one trial (63 participants) contributed to comparison 3, where there was a lack of evidence for an effect of the vegan dietary intervention on lipid levels or blood pressure compared to other dietary interventions (low- or very low-certainty evidence). Four trials reported on adverse events, which were absent or minor.
AUTHORS' CONCLUSIONS
Studies were generally small with few participants contributing to each comparison group. None of the included studies report on CVD clinical events. There is currently insufficient information to draw conclusions about the effects of vegan dietary interventions on CVD risk factors. The eight ongoing studies identified will add to the evidence base, with all eight reporting on primary prevention. There is a paucity of evidence for secondary prevention.
Topics: Adult; Bias; Blood Pressure; Cardiovascular Diseases; Cholesterol; Diet, Vegan; Female; Humans; Male; Middle Aged; Primary Prevention; Randomized Controlled Trials as Topic; Recurrence; Secondary Prevention; Triglycerides
PubMed: 33629376
DOI: 10.1002/14651858.CD013501.pub2 -
The British Journal of Nutrition Nov 2015Weight loss is crucial for treating type 2 diabetes mellitus (T2DM). It remains unclear which dietary intervention is best for optimising glycaemic control, or whether... (Review)
Review
The effect of macronutrients on glycaemic control: a systematic review of dietary randomised controlled trials in overweight and obese adults with type 2 diabetes in which there was no difference in weight loss between treatment groups.
Weight loss is crucial for treating type 2 diabetes mellitus (T2DM). It remains unclear which dietary intervention is best for optimising glycaemic control, or whether weight loss itself is the main reason behind observed improvements. The objective of this study was to assess the effects of various dietary interventions on glycaemic control in overweight and obese adults with T2DM when controlling for weight loss between dietary interventions. A systematic review of randomised controlled trials (RCT) was conducted. Electronic searches of Medline, Embase, Cinahl and Web of Science databases were conducted. Inclusion criteria included RCT with minimum 6 months duration, with participants having BMI≥25·0 kg/m2, a diagnosis of T2DM using HbA1c, and no statistically significant difference in mean weight loss at the end point of intervention between dietary arms. Results showed that eleven studies met the inclusion criteria. Only four RCT indicated the benefit of a particular dietary intervention over another in improving HbA1c levels, including the Mediterranean, vegan and low glycaemic index (GI) diets. However the findings from one of the four studies showing a significant benefit are questionable because of failure to control for diabetes medications and poor adherence to the prescribed diets. In conclusion there is currently insufficient evidence to suggest that any particular diet is superior in treating overweight and obese patients with T2DM. Although the Mediterranean, vegan and low-GI diets appear to be promising, further research that controls for weight loss and the effects of diabetes medications in larger samples is needed.
Topics: Blood Glucose; Diabetes Mellitus, Type 2; Diet; Diet, Mediterranean; Diet, Vegan; Glycated Hemoglobin; Glycemic Index; Humans; MEDLINE; Obesity; Overweight; Randomized Controlled Trials as Topic; Weight Loss
PubMed: 26411958
DOI: 10.1017/S0007114515003475 -
Advances in Nutrition (Bethesda, Md.) May 2019Dietary patterns with substantial proportions of energy from plant sources have been associated with favorable biomarkers of low-grade inflammation. Less is known of the... (Meta-Analysis)
Meta-Analysis
Dietary patterns with substantial proportions of energy from plant sources have been associated with favorable biomarkers of low-grade inflammation. Less is known of the relation between vegetarian-based dietary patterns and markers of inflammation and immune status. This systematic review and meta-analysis aimed to determine the relation between vegetarian-based dietary patterns and inflammatory and immune markers (C-reactive protein, tumour necrosis factor α, fibrinogen, natural killer cells, leukocytes, lymphocytes, thrombocytes, interleukins, and immunoglobulins). PubMed, Medline, and Cochrane scientific databases were searched to identify relevant studies. Random effects meta-analyses were conducted to assess the weighted mean differences (WMDs) for each outcome variable between vegetarian and non-vegetarian groups. Thirty observational and 10 intervention studies were included in the review. Pooled effects of vegetarian-based dietary patterns were associated with significantly lower concentrations of CRP (WMD: -0.61 mg/L; 95% CI: -0.91, -0.32 mg/L; P = 0.0001), fibrinogen (WMD: -0.22 g/L; 95% CI: -0.41, -0.04 mg/L; P = 0.02), and total leukocyte (WMD: -0.62 × 10(3)/μL; 95% CI -1.13 × 10(3), -0.10 × 10(3)/μL; P = 0.02) compared with those following non-vegetarian dietary patterns in observational studies. Insufficient data were identified for a meta-analysis of intervention studies. This study provides evidence that vegetarian-based dietary patterns are associated with lowered serum C-reactive protein, fibrinogen, and total leukocyte concentrations. Future research should focus on large-scale intervention trials, contrasting differences in inflammation and immune status and function between vegetarian and non-vegetarian-based populations.
Topics: Biomarkers; Blood Proteins; C-Reactive Protein; Diet, Vegetarian; Humans; Inflammation; Inflammation Mediators
PubMed: 30947338
DOI: 10.1093/advances/nmy103