Low glycemic index bean diet improved HbA1c, BP

Eating at least a cup of beans per day for three months lowered diabetic patients' hemoglobin A1c (HbA1c) scores and blood pressure, a new study found.

The trial randomized 121 patients with type 2 diabetes to either a low glycemic index diet (increasing daily bean consumption by at least one cup per day) or a diet higher in insoluble fiber (consumption of more whole wheat products). Participants reported their consumption for three months, and the primary outcome of the study was change in HbA1c. Results were published by Archives of Internal Medicine on Oct. 22.

The bean-eating group reduced their HbA1cs by 0.5% (95% CI, 0.6% to 0.4%) compared to a 0.3% reduction (95% CI, 0.4% to 0.2%) in the whole wheat group. They also showed significant improvement in blood pressure (−4.5 mm Hg systolic [95% CI, −7.0 to −2.0 mm Hg]) and heart rate, compared to no change in the wheat-eating group. Thanks to these changes in risk factors, the bean group also had a greater reduction in their coronary heart disease risk score.

Study authors concluded that incorporating legumes into a low glycemic index diet improved blood sugar control and coronary heart disease risk scores and could perhaps be analogous to the effect of acarbose (which has been associated with reductions in hypertension). The use of whole wheat as a positive control might have minimized the treatment difference, they added. This finding could be important, especially for patients from cultures in which traditional high bean intake has been replaced with Western diets, they concluded.

However, an accompanying commentary cautioned that the observed benefits from the bean diet could also be attributed to reduced calorie intake. Evidence on the association between glycemic index or dietary fiber consumption and health of patients with type 2 diabetes has been mixed and the issue is controversial, the commentary said. Legumes can certainly be components of a healthy diet, for people with and without diabetes, but no single nutritional therapy can be proven best for all patients with diabetes, the commentary concluded.