Recipe for Type 2 Diabetes: More Beans
A new study has spilled the beans about, well, beans, lentils and other legumes. Although legumes have a low glycemic index that is highly recommended for people with type 2 diabetes, no study has specifically examined using these foods for glycemic control as well as reduce the risk of coronary heart disease--until now.
Do you know beans?
Individuals with type 2 diabetes are encouraged to chose much of their food from those with a low glycemic index. The glycemic index is a measure of how quickly blood glucose (sugar) levels rise after eating. Thus foods with a low glycemic index (less than 55) help keep blood sugar levels low while those with a high index (higher than 70; e.g., white bread, doughnuts) can cause those levels to rise quickly and spike.
Foods with a glycemic index of less than 55 are considered low, and beans, lentils, and other legumes fit comfortably in that category. Therefore they were the focus of a randomized controlled trial, the results of which appear in Online First by Archives of Internal Medicine.
A total of 121 individuals with type 2 diabetes who were taking an antidiabetic medication were enrolled in the study. They were assigned to one of two groups: one in which participants were encouraged to increase the amount of legumes they ate per day by at least one cup, or one in which they were asked to increase the amount of whole wheat foods (high in insoluble fiber).
All the participants received a list of recommended foods and quantities for their assigned group, and they were asked to keep food records throughout the study. At the start of the three-month trial and also at weeks 2, 4, 8, 10, and 12, the participants were evaluated for weight, waist circumference, blood pressure, and fasting blood glucose.
Most (114) of the participants completed the study: 56 of 60 in the legume group and 58 of 61 in the wheat fiber group. Keeping in mind that the primary outcome measure of the study was changes in hemoglobin A1c (HbA1c) and that cardiovascular risk was the secondary outcome, here is a synopsis of the findings:
- The mean HbA1c declines by 0.5% in the legume group and by 0.3% in the wheat fiber group
- Participants in both groups experienced a significant reduction in body weight: a mean of 2.7 kg (6 lb) in the legume group and 2.0 kg (4.4 lb) in the wheat group
- Total cholesterol and triglyceride levels dropped a significant amount (mean, 8 mg/dL and 22 mg/dL, respectively) in the legume group only
- Good cholesterol (high-density lipoprotein, HDL) rose a significant amount in the wheat fiber group only
- Compared with the wheat fiber group, participants in the legume group had a reduction in both blood pressure (BP; mean 4.5 mmHg systolic and 3.1 mmHg diastolic) and heart rate (mean, 3.1 beats per minute)
- Risk of cardiovascular events was reduced in the legume group compared with the wheat fiber group, but the difference was not significant
According to David J.A. Jenkins, MD, of the University of Toronto and St. Michael's Hospital, and his team, "legume consumption of approximately 190 grams per day (1 cup) seems to contribute usefully to a low-GI diet and reduce CHD risk through a reduction in BP." The findings caused the authors to support the consumption of beans among people who already eat them and to reintroduce them into the Western diet.
Here are the glycemic index levels of some beans and other legumes. Note these are for legumes prepared from dried, not canned sources, and for 150 grams (about 5 ounces).
- Black beans, 30
- Black eyes peas, 33
- Chickpeas, 10
- Kidney beans, 29
- Lentils, 29
- Navy beans, 31
- Soybeans 15
A meta-analysis from 2009 that included legumes as part of a low glycemic index or high fiber study showed a 0.48 percent decline in HbA1c, similar to the 0.5 percent reduction in this new study. The Food and Drug Administration has stated that a 0.3 to 0.4 percent decline in HbA1c levels is therapeutically significant.
This new study is believed to be the first to promote the consumption of legumes as the main factor in a low-glycemic index diet for treatment of type 2 diabetes and to specify the amount of legumes participants ate. One recipe for better management of type 2 diabetes appears to be more beans.
Jenkins DJA et al. Effect of legumes as part of a low glycemic index diet on glycemic control and cardiovascular risk factors in type 2 diabetes mellitus. Archives of Internal Medicine, published online Oct. 22, 2012. doi: 10.1001/2013.jamainternmed.70
Sievenpiper JL et al. Effect of non-oil-seed pulses on glycaemic control: a systematic review and meta-analysis of randomised controlled experimental trials in people with and without diabetes. Diabetologia. 2009;52(8):1479-1495