Role of Low-Glycemic-Index Foods in Improving Overall Glycemic Control in Type 1 and Type 2 Diabetic Patients and Correcting Excessive Postprandial Hyperglycemia

Abstract

Increasing postprandial plasma glucose and insulin excursions are assumed to increase severity of diabetes and to be independent predictors of risk for atherosclerotic diseases and adiposity. Many possible connections have been found between postprandial events and the development of diabetes complication [1]. Lowering postprandial plasma glucose and insulin responses is relevant in preventing and managing diabetes mellitus [2,3]. Therefore, intervention towards reducing postprandial plasma glucose and insulin spikes is an essential topic in therapeutic strategy for diabetic patients, and may reduce the risk of developing cardiovascular complications. There is growing recognition that the postprandial glycemic [4,5] and insulinemic [6] responses to different foods may vary despite equal amounts of total absorbable carbohydrates, thus favoring low-glycemic-index (GI) carbohydrates. The notion of glycemic index was proposed by David Jenkins and et al. [5] more than twenty years ago as a practical way of classifying carbohydrate-containing foods according to their effect on postprandial blood glucose rather than according to carbohydrate content alone. The Gl is defined as the incremental area under the blood-glucose response curve of a 50 carbohydrate test food portion expressed as the percentage of the response to the same amount of carbohydrate from standard food (glucose, or white bread) taken by the same subject [7]. In practice, the actual carbohydrate load from a normal portion size varies considerably. Both type and amount of carbohydrate have now widely accepted influences on glycemic response [8,9]. In order to address this problem, the concept of glycemic load (GL) was introduced. GL, calculated as the amount of carbohydrate in one serving multiplied by the GI of the food, allows comparisons between likely glycemic effects of different foods in realistic portions [10]. However, GL values should be considered with caution, as both a low-GI/high-CHO food and a high GI/low-CHO food can have the same GL with different metabolic effects on β-cell function and plasma lipids [8]. Separate use of GL may lead to habitual consumption of low-carbohydrate diets. While short-term beneficial effects could be induced by low-carbohydrate diet, the long-term effects might be harmful. All the centers over the world that have tested experimental and clinical use of low-GI foods are enthusiastic about diet counseling to diabetic or hyperlipidemic patients, and even normal subjects at risk of cardiovascular diseases. A large number of studies have indeed demonstrated the efficiency of diet counseling and the use of low glycemic index (low-GI) foods in these patients. More striking effects were noted in the improvement of postprandial blood glucose excursions and, consequently, in glycated hemoglobin, fasting plasma lipids - particularly triglyceride levels - and, marginally, total and LDL cholesterol. We will give some insights on a few of our clinical and experimental results on this topic. At this stage, we would like to point out that the use of low-GI foods is only part of a more general strategy to improve postprandial hyperglycemia, and thus overall blood glucose control.