Diabetes patients who incorporate legumes as part of a low glycemic index (GI) diet improve their glycemic control and reduce their risk for coronary heart disease (CHD), a study shows.
David Jenkins (University of Toronto, Ontario, Canada) and colleagues found that participants who increased their legume (beans, chickpeas, lentils) intake by one cup each day experienced reduced glycated hemoglobin (HbA1c) and risk for CHD in comparison with participants who increased their insoluble fiber by consumption of wholewheat products for 3 months.
Indeed, the low-GI legume diet reduced HbA1c values by 0.5%, while the high-wheat-fiber diet reduced HbA1c values by 0.3%. The relative reduction in HbA1c values after the low-GI legume diet was significantly greater than that after the high-wheat-fiber diet.
Moreover, individuals on the low-GI legume diet had a 0.8% reduced risk for CHD relative to those on the high-wheat-fiber diet. This was primarily driven by a greater relative reduction of 4.5 mmHg in systolic blood pressure (BP) on the low-GI legume diet compared with the high-wheat-fiber diet.
The randomized controlled trial included 121 participants with type 2 diabetes.
"These data provide support for the use of legumes as a specific food option to lower the dietary GI in type 2 diabetes mellitus and for the recommendations to increase low-GI food consumption by many national diabetes associations," write the authors in the Archives of Internal Medicine.
Jenkins and team say that the exact mechanisms for the BP reduction associated with legume intake are unknown, but suggest that peptides digested from proteins may have antihypertensive effects when absorbed. They also point out that beans specifically are good sources of potassium and magnesium, which may reduce BP and "by virtue of their low GI are likely to result in lower postprandial insulin levels, associated with reduced salt retention and lower BP."
In a related editorial, Marion Franz (Nutrition Concepts by Franz Inc, Minneapolis, USA) argues that whether diabetic individuals can eat the amount of legumes necessary to improve glycemic control is "debatable" and asks if legumes do improve glycemia, whether it is due to their low GI or high soluble fiber content.
"Nutrition therapy for diabetes mellitus is effective. However, just as there is no one medication or insulin regimen appropriate for all persons with diabetes mellitus, there is no one nutrition therapy intervention," she says.
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