Low Glycemic Index Breads, Pasta, Peas and Lentils better for glycemic control of Type-2 diabetes than Whole Grain Breads and Whole Grain Cereals
Toronto, December 17, 2008
Study by Dr. David Jenkins also shows low-GI diet improves cardiovascular risk factors
Low-glycemic foods -- beans, peas, lentils, pasta, rice boiled briefly and breads like pumpernickel and flaxseed – do a better job of managing glycemic control for Type-2 diabetes and risk factors for coronary heart disease than high-fiber diets, including whole grain breads, crackers and breakfast cereals.
The study, Effect of a Low-Glycemic Index or a High-Cereal Fiber Diet on Type-2 Diabetes, is published in the December 17 issue of JAMA. Dr. David J. A. Jenkins, a doctor at St. Michael’s Hospital and a professor at the University of Toronto Faculty of Medicine’s Department of Nutritional Sciences, is the lead author.
“At a time when the incidence of Type-2 diabetes is likely to double in the next 20 years, any information that refines how we can manage this disease better is welcome. Our study shows that a low-GI diet can also minimize the risk factors associated with cardiovascular disease. It does this better than a diet high in fiber, but with a higher glycemic index,” said Dr. Jenkins. “Pharmaceuticals used to control Type-2 diabetes have not shown the expected benefits in terms of reducing cardiovascular disease. Our hope is that the low GI diet may help all the complications of diabetes.”
The study assessed the effects of a low–glycemic index diet versus a high–cereal fiber diet on glycemic control and cardiovascular risk factors for 210 patients with Type-2 diabetes. The participants, who were treated with antihyperglycemic medications, were randomly assigned to receive one of the two diet treatments for six months.
In the low–glycemic index diet, the following foods were emphasized: beans, peas, lentils, pasta, rice boiled briefly and low–glycemic index breads (including pumpernickel, rye pita, and quinoa bread with flaxseed) and breakfast cereals (including large flake oatmeal and oat bran). In the high–cereal fiber diet, participants were advised to take the “brown” option (whole grain breads; whole grain breakfast cereals; brown rice; potatoes with skins; and whole wheat bread, crackers, and breakfast cereals). Three servings of fruit and five servings of vegetables were encouraged on both treatments but temperate climate fruit (apples, pears, oranges and berries) was advised on the low GI diet.
The researchers found that hemoglobin A1c (HbA1c; a substance in red blood cells tested to measure the blood glucose level) decreased by –0.50 percent absolute HbA1c units in the low–glycemic index diet compared with –0.18 percent absolute HbA1c units in the high–cereal fiber diet. Significant treatment effects were observed for high-density lipoprotein cholesterol (HDL-C) and the low-density lipoprotein cholesterol (LDL-C): HDL-C ratio. HDL-C increased in the low–glycemic index diet group by 1.7 mg/dL and decreased by –0.2 mg/dL in the high– cereal fiber diet group. The LDL-C:HDL-C ratio showed a greater reduction in the low–glycemic index diet group compared with the high–cereal fiber diet group.
According to the Canadian Diabetes Association, diabetes is a worldwide pandemic. More than 2-million Canadians have diabetes. The number is dramatically increasing due to a number of factors, including an aging population, an increase in obesity, and sedentary lifestyles. Unmanaged, diabetes can contribute to heart disease, stroke, kidney disease and blindness.
About Dr. Jenkins
Dr. Jenkins researches how diet can help in the prevention and treatment of hyperlipidemia and diabetes. His team was the first to define and explore the concept of the glycemic index of foods and demonstrate the breadth of metabolic effects of viscous soluble fiber, including blood glucose and cholesterol lowering. His studies on combining cholesterol lowering food components (dietary portfolio) have been recognized as creating an effective dietary alternative to drug therapy (statins). To make therapeutic diets more accessible, he works with the food industry to develop products for supermarkets with specific health attributes and, for example, has been a Loblaw chief nutrition advisor for 20 years. Many of the foods under the President’s Choice Blue Menu program, which was created to provide consumers with healthier food, have been developed with Dr. Jenkins’ input. He is a Canada Research Chair at the University of Toronto and St. Michael’s Hospital.
About St. Michael’s Hospital
St. Michael's Hospital is a large and vibrant, teaching and research hospital in the heart of Toronto. Fully affiliated with the University of Toronto, St. Michael’s Hospital leads with innovation, and serves with compassion. Renowned for providing exceptional patient care, St. Michael’s Hospital is a regional trauma centre and downtown Toronto’s designated adult trauma centre.
About University of Toronto
Established in 1827, the University of Toronto is Canada's largest and most influential university with almost 12,000 faculty and staff working at three campuses and ten academic hospitals in the Toronto region. Our world-leading scholars teach more than 60,000 students in 841 distinct undergraduate programs as well as 520 graduate and 42 professional programs. According to Thomson ISI data, U of T faculty also publish more research than any other publicly-funded university in North America. And with over 400,000 alumni in more than 130 countries around the world, U of T is truly global in reach and impact.