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Low Glycemic Index/Load Dietary Patterns and Glycemia and Cardiometabolic Risk Factors in Diabetes: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

ABSTRACT: Abstract

Objectives

Low-glycemic index (GI) and load (GL) dietary patterns are recommended for diabetes management by clinical practice guidelines globally. To inform the update of the European Association for the Study of Diabetes (EASD) clinical practice guidelines for nutrition therapy, we conducted a systematic review and meta-analysis on the effect of low-GI/GL dietary patterns on glycemic control and other established cardiometabolic risk factors in type 1 and 2 diabetes.

Methods

MEDLINE, EMBASE, and the Cochrane Library were searched through November 2020. We included randomized controlled trials ≥3-weeks investigating the effect of low-GI/GL diets in diabetes. The primary outcome was HbA1c. Two independent reviewers extracted data and assessed risk of bias. GRADE (grading of recommendations assessment, development, and evaluation) assessed the certainty of the evidence. (ClinicalTrials.gov identifier, NCT04045938)

Results

We identified 30 trial comparisons in 1,672 participants with type 1 and 2 diabetes who were predominantly middle-aged, overweight or obese with moderately controlled type 2 diabetes treated by antihyperglycemic agents and/or insulin. Low-GI/GL dietary patterns significantly reduced HbA1c compared with higher-GI/GL control diets (mean difference −0.32% [95% confidence interval −0.48, −0.16%], P < 0.001; substantial heterogeneity, I2 = 74%, P < 0.001). There were also significant reductions in several secondary outcomes: fasting glucose, LDL-C, non-HDL-C, body weight, BMI, and CRP (P < 0.05), but not insulin or blood pressure. The certainty of evidence was moderate for the reduction in HbA1c and most secondary outcomes.

Conclusions

Our synthesis indicates that low-GI/GL dietary patterns improve established targets of glycemic control, blood lipids, adiposity and inflammation beyond concurrent therapy with antihyperglycemic agents and/or insulin in moderately controlled type 1 and type 2 diabetes. The available evidence provides a good indication of the likely benefit in this population with moderate likelihood that more research will alter our conclusions.

Funding Sources

Diabetes and Nutrition Study Group of the EASD, CIHR.

SUBMITTER: Chiavaroli L

PROVIDER: S-EPMC8180781 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:ObjectiveTo inform the update of the European Association for the Study of Diabetes clinical practice guidelines for nutrition therapy.DesignSystematic review and meta-analysis of randomised controlled trials.Data sourcesMedline, Embase, and the Cochrane Library searched up to 13 May 2021.Eligibility criteria for selecting studiesRandomised controlled trials of three or more weeks investigating the effect of diets with low glycaemic index (GI)/glycaemic load (GL) in diabetes.Outcome and measuresThe primary outcome was glycated haemoglobin (HbA1c). Secondary outcomes included other markers of glycaemic control (fasting glucose, fasting insulin); blood lipids (low density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C), non-HDL-C, apo B, triglycerides); adiposity (body weight, BMI (body mass index), waist circumference), blood pressure (systolic blood pressure (SBP) and diastolic blood pressure (DBP)), and inflammation (C reactive protein (CRP)).Data extraction and synthesisTwo independent reviewers extracted data and assessed risk of bias. Data were pooled by random effects models. GRADE (grading of recommendations assessment, development, and evaluation) was used to assess the certainty of evidence.Results29 trial comparisons were identified in 1617 participants with type 1 and 2 diabetes who were predominantly middle aged, overweight, or obese with moderately controlled type 2 diabetes treated by hyperglycaemia drugs or insulin. Low GI/GL dietary patterns reduced HbA1c in comparison with higher GI/GL control diets (mean difference −0.31% (95% confidence interval −0.42 to −0.19%), P<0.001; substantial heterogeneity, I2=75%, P<0.001). Reductions occurred also in fasting glucose, LDL-C, non-HDL-C, apo B, triglycerides, body weight, BMI, systolic blood pressure (dose-response), and CRP (P<0.05), but not blood insulin, HDL-C, waist circumference, or diastolic blood pressure. A positive dose-response gradient was seen for the difference in GL and HbA1c and for absolute dietary GI and SBP (P<0.05). The certainty of evidence was high for the reduction in HbA1c and moderate for most secondary outcomes, with downgrades due mainly to imprecision.ConclusionsThis synthesis suggests that low GI/GL dietary patterns result in small important improvements in established targets of glycaemic control, blood lipids, adiposity, blood pressure, and inflammation beyond concurrent treatment with hyperglycaemia drugs or insulin, predominantly in adults with moderately controlled type 1 and type 2 diabetes. The available evidence provides a good indication of the likely benefit in this population.Study registrationClinicalTrials.gov NCT04045938.

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