Effect of Legumes as Part of a Low Glycemic Index Diet on Glycemic Control and Cardiovascular Risk Factors in Type 2 Diabetes Mellitus

TLDR

Legumes are among the lowest glycemic‑index foods and are recommended in diabetes guidelines, yet they have not previously been used to lower the overall dietary GI. The study aimed to evaluate the effect of a low‑GI diet enriched with legumes on glycemic control in type 2 diabetes. 121 participants with type 2 diabetes were randomized for 3 months to a low‑GI legume diet (≥1 cup/day) or a high‑wheat‑fiber diet, with HbA1c and calculated CHD risk as primary outcomes. The legume diet lowered HbA1c by 0.5 % versus 0.3 % for wheat, a 0.2 % greater reduction (P < 0.001), and reduced CHD risk by 0.8 % (P = 0.003), largely due to a larger systolic blood‑pressure drop.

Abstract

<h3>Background</h3>Legumes, including beans, chickpeas, and lentils, are among the lowest glycemic index (GI) foods and have been recommended in national diabetes mellitus (DM) guidelines. Yet, to our knowledge, they have never been used specifically to lower the GI of the diet. We have therefore undertaken a study of low-GI foods in type 2 DM with a focus on legumes in the intervention.<h3>Methods</h3>A total of 121 participants with type 2 DM were randomized to either a low-GI legume diet that encouraged participants to increase legume intake by at least 1 cup per day, or to increase insoluble fiber by consumption of whole wheat products, for 3 months. The primary outcome was change in hemoglobin A_1c (HbA_1c) values with calculated coronary heart disease (CHD) risk score as a secondary outcome.<h3>Results</h3>The low-GI legume diet reduced HbA_1c values by −0.5% (95% CI, −0.6% to −0.4%) and the high wheat fiber diet reduced HbA_1c values by −0.3% (95% CI, −0.4% to −0.2%). The relative reduction in HbA_1c values after the low-GI legume diet was greater than after the high wheat fiber diet by −0.2% (95% CI, −0.3% to −0.1%; P &lt; .001). The respective CHD risk reduction on the low-GI legume diet was −0.8% (95% CI, −1.4% to −0.3%; P = .003), largely owing to a greater relative reduction in systolic blood pressure on the low-GI legume diet compared with the high wheat fiber diet (−4.5 mm Hg; 95% CI, −7.0 to −2.1 mm Hg; P &lt; .001).<h3>Conclusion</h3>Incorporation of legumes as part of a low-GI diet improved both glycemic control and reduced calculated CHD risk score in type 2 DM.<h3>Trial Registration</h3>clinicaltrials.gov Identifier: NCT01063361