Beans or Lentils Reduce Risk of Heart Attacks and Strokes

Researchers found that compared with a diet rich in whole grains, getting a daily dose of legumes led to a drop in an important measure of blood sugar as well as in blood pressure and cholesterol levels.

After three months on the bean diet, study participants' estimated 10-year risk of cardiovascular disease had fallen from 10.7 percent to 9.6 percent, according to the group.

David Jenkins of St. Michael's Hospital in Toronto, who led the study stated that, "Legumes are good protein sources, and proteins tend to dampen the blood glucose response and they lower blood pressure."

"They are also good sources of fiber and that tends to be associated with lower cholesterol."

Legumes such as beans, chickpeas and lentils are already recommended for diabetics due to their low glycemic index, a measure of how far and how fast a given food sends up blood sugar. But there are few studies of their direct effects on diabetes, according to Jenkins.

Jenkins and his team divided 121 people with diabetes into two groups, one of which was instructed to up their intake of cooked legumes by at least a cup a day. The other was told to eat more whole wheat products to boost their fiber intake.

After three months, the researchers found that hemoglobin A1c levels had dropped from 7.4 percent to 6.9 percent in people eating beans, while it had fallen from 7.2 percent to 6.9 percent tin those getting extra whole wheat. The number reflects the average blood sugar levels over the previous two to three months. Experts recommend keeping it under 7 percent.

Jenkins said that even though the drops were not huge, they were impressive partly because the whole-grain comparison diet is a healthy one and in part because people in the study were already on diabetes and blood pressure drugs.

There was no reduction in blood pressure with extra whole wheat, but a drop from 122 to 118 points in systolic blood pressure - the top number - with legumes and from 72 to 69 in diastolic. Blood pressure readings are considered normal is they are no more than 120 over 80.

Given the lower blood pressure, Jenkins and his colleagues calculated that diabetics getting a daily dose of beans would lower their 10-year risk of heart attack or stroke by just under one percentage point compared with people eating whole wheat.

By comparison, cholesterol-lowering drugs are thought to cut 10-year cardiovascular risk by about 20 percent, or two percentage points in people with a baseline risk of 10 percent. 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.

The study didn't find any more gastrointestinal complaints in the legume group, apparently refuting the notion that downing lots of beans leads to excessive flatulence. Jenkins did warn, though, that the comparison group also got a lot of fiber, which could have prevented a potential effect.

• The study found that eating more legumes such as beans and chickpeas may help improve glycemic control in patients with type 2 diabetes.
• Note that the legume diet significantly lowered mean total cholesterol and triglycerides, without any changes in HDL cholesterol levels.

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" Arch Intern Med 2012; DOI: 10.1001/2013.jamainternmed.70.