What is the glycaemic load (GL)? The glycaemic load (GL) is a newer concept that has been developed to help better reflect the glycaemic effects of food products. The GL is defined as a system for ranking the carbohydrate content in food products based on the glycaemic index (GI) and serving size. The GI is an in vivo measure of the effect that a carbohydrate containing food has on blood glucose levels compared to the effect of the same amount of pure glucose, on blood glucose levels. A problem with the GI is that it doesn’t provide an accurate overview of the entire glucose raising potential of carbohydrates in food products because the blood glucose response not only on quality but also the quantity of carbohydrates consumed. The glycaemic load captures both the quantity and quality of the carbohydrates consumed, providing a more accurate picture of the glycaemic effect of foods.
How is the glycaemic load calculated?
The glycaemic load is calculated by multiplying the GI value of the food by the amount of carbohydrate the serving of food contains, divided by 100.
For example, the GL is determined as follows for a standard apple:
GI of a standard apple = 40 Carbohydrate
Content of a standard apple = 15
GL = (40 x 15) / 100 = 6
Often foods with low fibre and high carbohydrate levels have high GI and GL values, whereas those with high fibre contents have lower GLs.4 There are various factors that contribute to the GL of a food, such as: the types of sugar and starches in the food, it’s preparation method, fat, fibre and carbohydrate content, and serving size.
The following ranges are usually applied to determine the GL of a particular food:
- Low GL – 10 or less
- Medium GL – 11 to 19
- High GL – 20 or more
The following values are applied to define the GL per day:
- Low GL – less than 80
- High GL – more than 120
Low GL foods produce a more desirable, steadier and lower rise in blood glucose levels. Note that some low GL foods do not have high fibre levels, whereas some high fibre food products have a high GL. It is important to determine the GI and GL values through directed testing. There have been two types of available glucose from foods – rapidly available and slowly available glucose. Studies examining food products and available glucose levels have demonstrated significant correlation between these values and the direct glycaemic response and GI values. 1
Medical conditions & GL
Clinical studies have demonstrated that dietary GL is associated with cardiovascular diseases, diabetes and obesity. Multiple studies have shown that dietary GL is associated with an increased risk for cardiovascular disease.2 Dietary GL has also been shown to be inversely related to the level of HDL and directly related to triglyceride levels The majority of clinical trials performed in diabetic patients demonstrate reduced glycaemic and insulin responses to a low glycaemic index / load meal as compared with a high glycaemic index / load meal.3
For more detailed information on the glycaemic load and it’s clinical application in patient’s lifestyles, visit Glycaemic Load.
Or for more detailed information on the glycaemic index and it’s clinical application in patient’s lifestyles, visit Glycaemic Index.
- Behall KM, Scholfield DJ, Canary J. Effect of starch structure on glucose and insulin responses in adults. Am. J. Clin. Nutr. 1998, 47: 428-432.
- Liu S, Willett W, Stampfer M, et al. A prospective study of dietary glycemic load, carbohydrate intake, and risk of coronary heart disease in US women. Am J Clin Nutr 2000; 71:1455-61.
- Willett W, Manson J, Liu, S. Glycemic index, glycemic load, and risk of type 2 diabetes. Am J Clin Nutr 2002; 76:274.
- Willet W, GL Reflects Actual Carbohydrate Burden, 2006, [cited 20th June 2007] Available from URL: http://www.drfood.citymax.com/articles/article/3407261/49370.htm