Diet rich in beans, nuts better for blood sugar control: study
Last Updated: Tuesday, December 16, 2008 | 5:44 PM ET
CBC News
People with Type 2 diabetes who eat a diet rich in nuts, beans and lentils lower their risk of medical complications and achieve better control of blood sugar levels than with a diet lacking those foods, a new Canadian study suggests.
In Wednesday's issue of the Journal of the American Medical Association, Dr. David Jenkins of St. Michael's Hospital and the University of Toronto and his colleagues report that people who were randomly assigned to follow a so-called low-glycemic-index diet for six months showed lower blood glucose levels and higher healthy cholesterol levels than those who ate a diet rich in cereals.
The research attempts to resolve the question of the best way for people with Type 2 diabetes to avoid dangerously large, quick spikes in blood sugar. One theory has been that a diet with a low glycemic index — that is, foods that are digested more slowly and release sugar into the bloodstream more slowly — would be better for blood-sugar levels.
In the St. Michael's study, roughly half the 210 participants were fed such a diet, which included includes beans, peas, lentils and nuts, as well as pasta, rice boiled briefly, large-flake oatmeal, oat bran and pumpernickel, rye, pita, quinoa and flaxseed breads.
A second group was fed a high-cereal diet that included whole-grain breads and cereals, brown rice, potatoes with skins and whole-wheat bread and crackers. The high-cereal diet did not contain nuts, beans or lentils, which are among the foods with the lowest glycemic indexes.
Both groups were encouraged to eat three servings of fruit and five servings of vegetables. Nearly 83 per cent of all participants were overweight and their average age was 60. All participants were treated with at least one medication to lower their high blood sugar levels, but they did not take insulin injections.
The researchers found that hemoglobin A1c — a measure of blood glucose levels — decreased by 0.5 per cent on average in the low-glycemic index diet, and they speculate that such a reduction corresponds to a 10 per cent to 12 per cent drop in cardiovascular complications among diabetics. By comparison, those on the high-cereal fibre diet experienced an average 0.18 per cent fall in hemoglobin A1c, known as HbA1c.
"Diet may play a role in controlling both blood glucose and cardiovascular risk factors at the same time," Jenkins said.
"Healthy" or HDL cholesterol levels were also raised in the low-glycemic-index diet by an average 1.7 milligrams per decilitre of blood, but they decreased by 0.2 mg/dL in the high-cereal diet, the researchers found.
"These data have important implications for the treatment of diabetes where the goal has been tight glycemic control to avoid complications. The reduction in HbA1c was modest, but we think it has clinical relevance," the study's authors write.
The researchers suggest that people with Type 2 diabetes consider following a low-glycemic-index diet to keep the disease in check — especially since drugs have often failed to show a significant reduction in the higher rates of heart attacks and strokes seen among diabetics.
"So I think what this does," said Jenkins, "is this now gives another tool … for getting the blood glucose levels down, which is tremendously important to stop diabetics from going blind, losing their kidneys and succumbing to other problems."
About 60,000 new cases of Type 2 diabetes are diagnosed each year in Canada.
With files from Canadian Press
