Diets with Low Glycemic Index, Glycemic Load Can Improve Diabetes Control


A systematic review and meta-analysis of randomized clinical trial data suggest those adhering to diets with a low glycemic index and low glycemic load were linked to lowered HbA1c levels and improvements in cardiometabolic risk factors.

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Patient checking their blood sugar from a finger prick using a conventional glucose monitoring

New research suggests adherence to a diet with a low glycemic index and glycemic load could improve glycemic control and reduce cardiometabolic in patients with diabetes.

Conducted to provide evidence supporting updates to clinical practice guidelines for the European Association for the Study of Diabetes (EASD), the present systematic review and meta-analysis summarized the effect of low GI/GL dietary patterns on glycemic control in patients with type 1 and type 2 diabetes.

The team, led by John L Sievenpiper, MD, PhD, Department of Nutritional Sciences, Temerty Faculty of Medicine, University of Toronto, found low GI/GL dietary patterns had clinically significant reduction in the primary target of HbA1c and small clinically meaningful improvement in other cardiometabolic risk factors in patients with moderately controlled diabetes.


Searching the Medline, Embase, and the Cochrane Central Register of Controlled Trials databases from inception through May 2021, including RCTs with follow-up of ≥3 weeks investigating the effect of low GI/GL diet on glycemic control in patients with type 1 or type 2 diabetes.

A team of 2 investigators independently review data from each report, using a standardized form consisting of sample size, study design, GL/GL dose during intervention and control, follow-up, and outcome data.

The primary outcome of the analysis was the difference in glycated hemoglobin (HbA1c). Secondary outcomes included fasting glucose levels, low-density lipoprotein (LDL-C), high-density lipoprotein (HDL-C), adiposity, blood pressure, and inflammation (C - reactive protein).

Data on the mean difference between intervention and control arms were extracted and then used as the basis for analysis in each trial comparison.

Further, the team used the GRADE (grading of recommendations assessment, development, and evaluation) approach to assess overall certainty of evidence, in which it was graded as high, moderate, low, or very low certainty.


Investigators included a total of 27 reports containing data for 29 trial comparisons in the final analyses, with 1617 participants.

Trials had a median follow-up of 12 weeks, with an equal distribution of men and most patients (90%) with type 2 diabetes. Further, most patients were middle-aged (median age 56 years), overweight or obese (median BMI 31), with moderate glycemic (median baseline HbA1c 7.7%) treated with hyperglycemia or insulin.

For the primary outcome, investigators observed in those with mixed type 1 and type 2 diabetes, low GI/GL dietary patterns resulted in a reduction in HbA1c, compared with control diets with a mean difference of −0.31 (95% CI −0.42 to −0.19%), P <0.001; substantial heterogeneity, I2=75%, P <0.001).

In addition, investigators observed reductions from low GI/GL diets in non-HDL-C (mean difference -0.20 mmol/L; 95% CI, -0.33 to -0.07, P = .002), LDL-C (−0.17 mmol/L; 95% CI, −0.25 to −0.08, P <.001), apo B (−0.05 g/L; 95% CI, −0.09 to −0.01, P = .03), triglycerides (−0.09 mmol/L; 95% CI, −0.17 to −0.01, P = 0.04), BMI (−0.38; 95% CI, −0.64 to −0.13, P = .003, and CRP (−0.41 mg/L; 95% CI, −0.78 to −0.04, P = .03).

However, no reductions were observed in blood in HDL-C, waist circumference, or blood pressure.


Investigators concluded this analysis supported recommendations for the use of low GI/GL dietary patterns in the management of diabetes, with advantages in reducing HbA1c, as well as other cardiometabolic risk factors.

“The main source of uncertainty, imprecision, should be considered by further large high quality randomized controlled trials, which target lower GI/GL diets with bigger differences between test and control,” investigators wrote.

The study, “Effect of low glycaemic index or load dietary patterns on glycaemic control and cardiometabolic risk factors in diabetes: systematic review and meta-analysis of randomised controlled trials”, was published online in BMJ.

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