Glycemic index and glycemic load: measurement issues and their effect on diet–disease relationships

Abstract

Glycemic index (GI) describes the blood glucose response after consumption of a carbohydrate containing test food relative to a carbohydrate containing reference food, typically glucose or white bread. GI was originally designed for people with diabetes as a guide to food selection, advice being given to select foods with a low GI. The amount of food consumed is a major determinant of postprandial hyperglycemia, and the concept of glycemic load (GL) takes account of the GI of a food and the amount eaten. More recent recommendations regarding the potential of low GI and GL diets to reduce the risk of chronic diseases and to treat conditions other than diabetes, should be interpreted in the light of the individual variation in blood glucose levels and other methodological issues relating to measurement of GI and GL. Several factors explain the large inter-and intra-individual variation in glycemic response to foods. More reliable measurements of GI and GL of individual foods than are currently available can be obtained by studying, under standard conditions, a larger number of subjects than has typically been the case in the past. Meta-analyses suggest that foods with a low GI or GL may confer benefit in terms of glycemic control in diabetes and lipid management. However, low GI and GL foods can be energy dense and contain substantial amounts of sugars or undesirable fats that contribute to a diminished glycemic response. Therefore, functionality in terms of a low glycemic response alone does not necessarily justify a health claim. Most studies, which have demonstrated health benefits of low GI or GL involved naturally occurring and minimally processed carbohydrate containing cereals, vegetables and fruit. These foods have qualities other than their immediate impact on postprandial glycemia as a basis to recommend their consumption. When the GI or GL concepts are used to guide food choice, this should be done in the context of other nutritional indicators and when values have been reliably measured in a large group of individuals.

Organoleptic and glycemic properties of chickpea-wheat composite breads

“…These results emphasize the impact of glycemic load (GL) of a food on its glycemic response (Venn and Green 2007). Replacing whole-wheat flour with 25 % or 35 % chickpea flour might have reduced the amount of starch and thus the GL resulting in reduced glycemic effect.…”

“…Nutritional limitations of a wheat bread are its low content of essential amino acids (Hefnawy et al 2012) and its high GI (Foster-Powell et al 2002). However, GI is not solely responsible for the rise in blood glucose concentration with a carbohydrate food, glycemic response is also influenced by the glycemic load (GL) or the amount of high glycemic carbohydrate in the food (Venn and Green 2007). Habitual consumption of high GI foods at high GL is associated with tissue and organ damage such as microangiopathy, diabetic nephropathy or retinopathy whereas low GI foods consumed at moderate GL are associated with reduced rates of coronary arterial diseases and type-2 diabetes (Brownlee 2003;Liu et al 2000).…”

The effect of the fat and carbohydrate contents in the evening meal preceding GI testing on GI

“…There is some evidence to suggest that choosing foods with a low GI is helpful in managing glycaemic control in type I and type II diabetes, and that low-GI diets may reduce the risk of several chronic diseases (Brand-Miller et al, 2003;Barclay et al, 2008;Jenkins et al, 2008;Wolever et al, 2008a). However, the role for GI in the prevention and treatment of diseases is not entirely clear (Venn and Green, 2007). Some of this lack of clarity may be due to methodological issues in that the reliability of GI is poor .…”

Glycaemic index: challenges in translating concept to practice

“…The rates of digestion of carbohydrates also vary with health status, race, gender and underlying insulin resistance all of which can affect GI [5]. Similarly, methodological differences such as the amount of tested food which contains 50 g of carbohydrate (available, absorbable, digestable), method of glucose measurement, time of day when the test was performed and the method of calculation of glucose response also affect GI values further complicating interpretation and limiting their value for day to day use [7].In vitro models for estimation of GI of different foods have been proposed to overcome the problem of variability. While these models have been accurate and reproducible, they do not take into account biological factors like differences of digestion, absorption and insulin resistance that can significantly impact GI [5].…”

“…The rates of digestion of carbohydrates also vary with health status, race, gender and underlying insulin resistance all of which can affect GI [5]. Similarly, methodological differences such as the amount of tested food which contains 50 g of carbohydrate (available, absorbable, digestable), method of glucose measurement, time of day when the test was performed and the method of calculation of glucose response also affect GI values further complicating interpretation and limiting their value for day to day use [7].…”