Glycaemic glucose equivalent: combining carbohydrate content, quantity and glycaemic index of foods for precision in glycaemia management

The glycaemic index (GI) is the blood glucose response to carbohydrate in a food as a percentage of the response to an equal weight of glucose. Because GI is a percentage, it is not related quantitatively to food intakes, and because it is based on equi-carbohydrate comparisons, GI-based exchanges for control of glycaemia should be restricted to foods providing equal carbohydrate doses. To overcome these limitations of GI, the glycaemic glucose equivalent (GGE), the weight of glucose having the same glycaemic impact as a given weight of food, is proposed as a practical measure of relative glycaemic impact. To illustrate the differences between GGE and GI in quantitative management of postprandial glycaemia, published values for carbohydrate content, GI and serving size of foods in the food groupings, breads, breakfast cereals, pulses, fruit and vegetables, were used to determine the GGE content per equal weight and per serving of foods. Food rankings and classifications for exchanges based on GGE content were compared with those based on GI. In all of the food groupings analysed, values for relative glycaemic impact (as GGE per 100 g food and per serving) within each of the categories, low, medium and high GI, were too scattered for GI to be a reliable indicator of the glycaemic impact of any given food. Correlations between GI and GGE content per serving were highest in food groupings of similar carbohydrate content and serving size, including breads (r = 0.73) and breakfast cereals (r = 0.8), but low in more varied groups including pulses (r = 0.66), fruit (r = 0.48) and vegetables (r = 0.28). Because of the non-correspondence of GI and GGE content, food rankings by GI did not agree with rankings by GGE content, and placement of foods in GI-based food exchange categories was often not appropriate for managing glycaemia. Effects of meal composition and food intake on relative glycaemic impact could be represented by GGE content, but not by GI. Because GGE is not restricted to equicarbohydrate comparisons, and is a function of food quantity, GGE may be applied, irrespective of food or meal composition and weight, and in a number of approaches to the management of glycaemia. Accurate control of postprandial glycaemia should therefore be achievable using GGE because they address the need to combine GI with carbohydrate dose in diets of varying composition and intake, to obtain a realistic indication of relative glycaemic impact.