Exploring the sense and nonsense of food and health

The Glycemic Index/Load: What is the Difference?

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The glycemic response is defined as the rate, magnitude and duration of the rise in blood glucose that occurs after a particular food or meal is consumed. It is affected by the amount of carbohydrate amount and type and the fat and protein in the food. Refined sugars and starches generally cause a greater glycemic response than unrefined carbohydrates that contain fiber. The presence of fat and protein also slows stomach emptying. For example, ice cream is high in sugar, but also contains fat and protein, so it causes a smaller rise in blood glucose than sorbet high in sugar but with less fat or protein.

This response can be quantified by its glycemic index (GI) defined as a ranking of the effect on blood glucose of a food of a certain carbohydrate content relative to an equal amount of carbohydrate from a reference food such as white bread or glucose.

The glycemic load (GL)  is a method of assessing the glycemic response that takes into account both the glycemic index of the food and the amount of carbohydrate in a typical portion. To calculate the GL, the grams of carbohydrate in a serving of food are multiplied by that food’s GI expressed as a percentage. For example, watermelon has a high GI of 70, but a much lower GL of 4.  The use of the glycemic load gives us a more true measure of its impact on the glycemic response. This tool is not very practical to use daily; however,  the concept is useful to understand  the impact of carbohydrate foods on blood glucose levels.

A glycemic load of:

  • 20 or more is high,
  • 11 to 19 is medium
  • 10 or under is low


Source: Smolin and Grosvenor, Nutrtiion, Science and Applications, Third Edition.

For a list of the GI and GL of 100 foods, CLICK HERE.





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