Effect of vegetarian dietary patterns on cardiometabolic risk factors in diabetes: A systematic review and meta-analysis of randomized controlled trials

  • Effie Viguiliouk
    Affiliations
    Toronto 3D (Diet, Digestive Tract and Disease) 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
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  • Cyril WC. Kendall
    Affiliations
    Toronto 3D (Diet, Digestive Tract and Disease) 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
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  • Hana Kahleová
    Affiliations
    Institute for Clinical and Experimental Medicine, Diabetes Centre, Prague, Czech Republic

    Physicians Committee for Responsible Medicine, Washington, DC, USA
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  • Dario Rahelić
    Affiliations
    Department of Endocrinology, Diabetes and Metabolic Diseases, Dubrava University Hospital, Zagreb, Croatia
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  • Jordi Salas-Salvadó
    Affiliations
    CIBER Fisiopatología de la Obesidad y Nutrición (CIBERObn), Instituto de Salud Carlos III, Madrid, Spain

    Human Nutrition Department, IISPV, Universitat Rovira i Virgili, Reus, Spain
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  • Vivian L. Choo
    Affiliations
    Toronto 3D (Diet, Digestive Tract and Disease) 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
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  • Sonia Blanco Mejia
    Affiliations
    Toronto 3D (Diet, Digestive Tract and Disease) 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
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  • Sarah E. Stewart
    Affiliations
    Toronto 3D (Diet, Digestive Tract and Disease) 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
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  • Lawrence A. Leiter
    Affiliations
    Toronto 3D (Diet, Digestive Tract and Disease) 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 & Metabolism, St. Michael's Hospital, Toronto, Canada

    Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Canada
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  • David JA. Jenkins
    Affiliations
    Toronto 3D (Diet, Digestive Tract and Disease) 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 & Metabolism, St. Michael's Hospital, Toronto, Canada

    Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Canada
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  • John L. Sievenpiper
    Correspondence
    Corresponding author. St. Michael's Hospital, #6137-61 Queen Street East, Toronto, ON, M5C 2T2, Canada. Fax: +1 416 867 7495.
    Affiliations
    Toronto 3D (Diet, Digestive Tract and Disease) 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 & Metabolism, St. Michael's Hospital, Toronto, Canada

    Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Canada
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      Summary

      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

      Keywords

      Abbreviations:

      ESM (electronic supplementary material), GRADE (Grading of Recommendations Assessment, Development, and Evaluation), MD (mean difference)
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