BACKGROUND & AIMS: To update the European Association for the Study of Diabetes (EASD) clinical practice guidelines for nutrition therapy, we conducted a systematic review and meta-analysis of randomized controlled trials to summarize the evidence for the effect of vegetarian dietary patterns on glycemic control and other established cardiometabolic risk factors in individuals with diabetes. METHODS: We searched MEDLINE, EMBASE, and Cochrane databases through February 26, 2018 for randomized controlled trials ≥3 weeks assessing the effect of vegetarian dietary patterns in individuals with diabetes. The primary outcome was HbA1c. Secondary outcomes included other markers of glycemic control, blood lipids, body weight/adiposity, and blood pressure. Two independent reviewers extracted data and assessed risk of bias. Data were pooled by the generic inverse variance method and expressed as mean differences (MD) with 95% CIs. Heterogeneity was assessed (Cochran Q statistic) and quantified (I2 statistic). The overall certainty of the evidence was assessed using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach. RESULTS: Nine trials (n = 664 participants) met the eligibility criteria. Vegetarian dietary patterns significantly lowered HbA1c (MD = -0.29% [95% CI: -0.45, -0.12%]), fasting glucose (MD = -0.56 mmol/L [95% CI: -0.99, -0.13 mmol/L]), LDL-C (MD = -0.12 mmol/L [95% CI: -0.20, -0.04 mmol/L]), non-HDL-C (MD = -0.13 mmol/L [95% CI: -0.26, -0.01 mmol/L]), body weight (MD = -2.15 kg [95% CI: -2.95, -1.34 kg]), BMI (MD = -0.74 kg/m2 [95% CI: -1.09, -0.39 kg/m2]) and waist circumference (MD = -2.86 cm [95% CI: -3.76, -1.96 cm]). There was no significant effect on fasting insulin, HDL-C, triglycerides or blood pressure. The overall certainty of evidence was moderate but was low for fasting insulin, triglycerides and waist circumference. CONCLUSION: Vegetarian dietary patterns improve glycemic control, LDL-C, non-HDL-C, and body weight/adiposity in individuals with diabetes, supporting their inclusion for diabetes management. More research is needed to improve our confidence in the estimates. CLINICALTRIALS. GOV IDENTIFIER: NCT02600377.

CIBER Fisiopatología de la Obesidad y Nutrición Instituto de Salud Carlos 3 Madrid Spain; Human Nutrition Department IISPV Universitat Rovira i Virgili Reus Spain

Department of Endocrinology Diabetes and Metabolic Diseases Dubrava University Hospital Zagreb Croatia

Institute for Clinical and Experimental Medicine Diabetes Centre Prague Czech Republic; Physicians Committee for Responsible Medicine Washington DC USA

Toronto 3D Knowledge Synthesis and Clinical Trials Unit Clinical Nutrition and Risk Factor Modification Center St Michael's Hospital Toronto Canada; Department of Nutritional Sciences Faculty of Medicine University of Toronto Toronto Canada

Toronto 3D Knowledge Synthesis and Clinical Trials Unit Clinical Nutrition and Risk Factor Modification Center St Michael's Hospital Toronto Canada; Department of Nutritional Sciences Faculty of Medicine University of Toronto Toronto Canada; College of Pharmacy and Nutrition University of Saskatchewan Saskatoon Canada

Toronto 3D Knowledge Synthesis and Clinical Trials Unit Clinical Nutrition and Risk Factor Modification Center St Michael's Hospital Toronto Canada; Department of Nutritional Sciences Faculty of Medicine University of Toronto Toronto Canada; Cumming School of Medicine University of Calgary Calgary Canada

Toronto 3D Knowledge Synthesis and Clinical Trials Unit Clinical Nutrition and Risk Factor Modification Center St Michael's Hospital Toronto Canada; Department of Nutritional Sciences Faculty of Medicine University of Toronto Toronto Canada; Department of Medicine University of Toronto Toronto Canada; Division of Endocrinology and Metabolism St Michael's Hospital Toronto Canada; Li Ka Shing Knowledge Institute St Michael's Hospital Toronto Canada

Toronto 3D Knowledge Synthesis and Clinical Trials Unit Clinical Nutrition and Risk Factor Modification Center St Michael's Hospital Toronto Canada; Department of Nutritional Sciences Faculty of Medicine University of Toronto Toronto Canada; Division of Endocrinology and Metabolism St Michael's Hospital Toronto Canada; Li Ka Shing Knowledge Institute St Michael's Hospital Toronto Canada

References provided by Crossref.org

Nordic dietary patterns and cardiometabolic outcomes: a systematic review and meta-analysis of prospective cohort studies and randomised controlled trials

Dietary Patterns and Cardiometabolic Outcomes in Diabetes: A Summary of Systematic Reviews and Meta-Analyses

Relation of Vegetarian Dietary Patterns With Major Cardiovascular Outcomes: A Systematic Review and Meta-Analysis of Prospective Cohort Studies

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NCT02600377