Eating more legumes such as beans and chickpeas helped improve glycemic control and lowered total cholesterol and triglycerieds in patients with type 2 diabetes, researchers found.

In a randomized controlled trial, patients who ate at least an additional cup of legumes per day had a greater reduction in HbA1c than patients who increased their insoluble fiber consumption for 3 months (-0.5% versus -0.3%, P<0.001), David Jenkins, MD, PhD, of the University of Toronto, and colleagues reported online in the Archives of Internal Medicine.

Foods with a low glycemic index (GI) have been shown to improve glycemic control in patients with type 2 diabetes, and legumes—such as beans, chickpeas, and lentils—were among the first foods recognized to have low GI values.

They’ve been recommended in many nutrition therapy guidelines for diabetes, but their effects on glycemic control and other parameters still remain controversial, researchers say.

So Jenkins and colleagues randomized 121 patients with type 2 diabetes to one of two diets for 3 months: a low-GI legume diet that required them to eat at least a cup of legumes per day, or to a diet that increased their intake of insoluble fiber via consumption of whole wheat products. The primary outcome was change in HbA1c, with a secondary endpoint of calculated coronary heart disease risk. The difference they found in HbA1c reduction remained significant after adjustment for body weight change, they reported (P=0.005). In terms of cardiac parameters, they found that the legume diet significantly lowered mean total cholesterol (-8 mg/dL, P<0.001) and triglycerides (-22 mg/dL, P<0.001), without any changes in HDL cholesterol levels. The insoluble fiber diet increased average HDL cholesterol levels (2 mg/dL, P=0.004), although the reasons for this are unclear, given that such an association hasn't been seen before in the literature, the researchers noted. And the legume diet reduced blood pressure and heart rate relative to the high insoluble fiber diet, they added. Thus, the legume diet overall reduced heart risk significantly more than the insoluble fiber diet (-0.8%, P=0.003), and the researchers concluded that incorporating legumes into a low-GI diet can help improve glycemic control and reduce heart risk. In an accompanying editorial, Marion Franz, MS, RD, questioned whether the modest benefits come from the dietary components or from a reduced energy intake overall. She warned that low-GI diet has been controversial, with some smaller studies showing a benefit in terms of improved glycemic control but larger studies showing no such benefit. Franz conceded that legumes are part of a healthy diet for diabetics and the general population, but "whether people with diabetes can eat the amount necessary to improve glycemic control is debatable, and, if legumes do improve glycemia, is it because of their low GI or high soluble fiber content?" She concluded that nutrition therapy for diabetes is effective but "just as there is no one medication or insulin regimen appropriate for all persons with diabetes, there is no one nutrition therapy intervention."