Glycaemic index methodology

Abstract

The glycaemic index (GI) concept was originally introduced to classify different sources of carbohydrate (CHO)-rich foods, usually having an energy content of . 80 % from CHO, to their effect on post-meal glycaemia. It was assumed to apply to foods that primarily deliver available CHO, causing hyperglycaemia. Low-GI foods were classified as being digested and absorbed slowly and high-GI foods as being rapidly digested and absorbed, resulting in different glycaemic responses. Low-GI foods were found to induce benefits on certain risk factors for CVD and diabetes. Accordingly it has been proposed that GI classification of foods and drinks could be useful to help consumers make 'healthy food choices' within specific food groups. Classification of foods according to their impact on blood glucose responses requires a standardised way of measuring such responses. The present review discusses the most relevant methodological considerations and highlights specific recommendations regarding number of subjects, sex, subject status, inclusion and exclusion criteria, pre-test conditions, CHO test dose, blood sampling procedures, sampling times, test randomisation and calculation of glycaemic response area under the curve. All together, these technical recommendations will help to implement or reinforce measurement of GI in laboratories and help to ensure quality of results. Since there is current international interest in alternative ways of expressing glycaemic responses to foods, some of these methods are discussed.

Breaking sitting with light activities vs structured exercise: a randomised crossover study demonstrating benefits for glycaemic control and insulin sensitivity in type 2 diabetes

“…Mean 24 h glucose concentration was defined as the average glucose of 288 measurements equally spaced in time. The incremental AUC (iAUC) for glucose was calculated using the trapezoid rule [23]. The iAUC provides a summary measure of the increase above fasting glucose level during the subsequent 24 h observation period.…”

Effects of breakfast meal composition on second meal metabolic responses in adults with type 2 diabetes mellitus

“…The glycemic index (GI) values of the psyllium loop and farina cereals were analyzed using white bread as reference and the results were 56 and 64, respectively. The GI of the mixed meal was not measured as the methodology has yielded mixed results (Brouns et al, 2005). The calculated difference between the low-glycemic load response breakfast meal containing psyllium soluble fiber was 38% lower than the high-glycemic load response breakfast meal.…”

Use of the glycemic index in nutrition education

“…Many internationally relevant agencies, like the Food and Agriculture Organization (FAO) 3 , European Association for the Study of Diabetes 6 and National Health and Medical Research Council of Australia 7 have recommended the consumption of low GI foods/diets to improve health. This recommendation is based on the establishment and diffusion of more appropriate methods for determining GI 2,3,8 , including more accurate determination of available carbohydrate content 9 , and the existence of studies that consolidate the importance of consuming low GI diets for preventing and treating diseases such as type 2 diabetes, cardiovascular diseases, obesity and some types of cancer [10][11][12][13] .…”

“…As an example, the GI of bananas varies from 47±5 for those grown in Australia to 70±5 for the ones from South Africa. For this reason, whenever possible, to increase accuracy one should prefer to use the values obtained for foods from his/her home country, as long as the GI has been determined in at least 10 non-diabetic individuals, as recommended by FAO 2,16 . Hence, international references should only be used when the domestic sources are not based on studies that used methodological rigorousness or when the GI of the food in question is not found.…”