Research published in the Archives of Internal Medicine on October 22 shows that subjects who consumed one cup of beans daily for three months were able to lower their blood sugar and blood pressure from their original levels, even more than another group who ate a high-wheat fiber diet.
"People with diabetes did better in terms of blood sugar control on the bean diet versus a diet without beans, which was otherwise extremely healthy," says researcher Dr. David J.A. Jenkins, professor of medicine and nutrition at the University of Toronto and St. Michael's Hospital in Toronto, said to WebMD.
Beans or legumes are considered low-glycemic index foods. The glycemic index orders food by how they affect a person's blood sugar level. High glycemic scores are digested quicker and cause a spike in blood sugar, which is often followed by a quick drop in blood sugar levels. Low foods are digested slowly and raise your blood sugar slowly.
Foods like white rice, watermelon and boiled red potatoes with skin are considered high on the index and have a score of 70 or up, according to the Mayo Clinic. Examples of low-glycemic foods include grapefruits, skim milk, raw carrots and apples, all of which receive a score of 55 and under. Medium foods, which score in the 56 to 69 range, include sweet corn, bananas and certain types of ice cream.
The study involved 121 men and women who had been diagnosed with Type 2 diabetes. Participants were assigned to a group that was instructed to eat a healthy diet high in wheat fiber or a group told to eat a healthy diet including a cup of legumes a day (about two servings). They were also given a checklist of recommended foods and qualities to ensure a balanced diet.
After three months, the bean group's blood sugar level as determined by the HbA1C test dropped 0.5%, while those on the wheat diet dropped 0.3%. The authors pointed out that 0.3 to 0.4 percentage drops in levels are thought to be meaningful by the Food and Drug Administration. Both groups were able to drop their blood sugar levels below 7%, which is recommended for for type 2 diabetics.
Blood pressure also dropped for participants. The bean-diet group started with 122/72mmHg and ended up with an average of 118/69mmHg. Wheat-diet participants started with 118/70mmHg and finished with with the same blood pressure. Normal blood pressure is considered to be 120/80mmHg.
"It reduced heart disease risk predominantly because of its effect on blood pressure," Jenkins said of the bean diet. "That came as a shock to us."
Samantha Heller, an exercise physiologist and clinical nutrition coordinator at the Center for Cancer Care at Griffin Hospital in Derby, Conn., said to HealthDay that the study shows that beans can help keep you healthy.
"For people with Type 2 diabetes, beans as part of an overall healthy diet are a great addition," Heller said. "Not only do legumes have a relatively low glycemic index, they are loaded with fiber, antioxidants, protein, vitamins and minerals."
The study was conducted on a small group of people who had their diabetes relatively controlled, so it has not been determined if the results can be replicated in a large group of people or people who do not treat their diabetes. Another possibility is that the high fiber content -- not the beans themselves -- may have provided the health benefits. Marion J. Franz, a nutrition/health consultant with Nutrition Concepts by Franz Inc., said in an invited commentary that glycemic index numbers have been controversial in the past.
"Legumes, as documented in the study by Jenkins et al, are components of a healthy eating pattern for people with DM (diabetes) and the general public. Whether people with DM 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 wrote in the commentary.
However, for now, the researchers and other experts feel confident in saying that eating beans cannot hurt, but could possibly help.
"Swap a few of your meat meals for bean stew," Jenkins said.