The glycemic index is a scale by which to measure how fast a certain food will raise blood sugar levels when consumed. Specifically, the glycemic index can be used to tell which foods will rapidly increase blood glucose levels (typically less healthy refined, simple carbohydrate foods) and which foods will not rapidly increase blood glucose levels (typically healthy whole-grain foods, vegetables, or fruits) when consumed.
Unfortunately, the glycemic index fails to account for the quantity of carbohydrates in a serving of food. As a result, the glycemic index can sometimes be misleading because it does not account for the quantity of a particular food that is consumed.
The Glycemic Load
The glycemic load (GL) solves this problem by measuring the quantity of carbohydrates in each serving of a particular food and then multiplying it by the glycemic index of that food. Thus, GL tells exactly what a particular serving size of food will due to blood sugar levels. The GL is consequently more useful for differentiating between “good” and “bad” carbohydrates.
A glycemic load of 1 to 10 is low; 11 to 19 is medium, and 20+ is high. (For a table with specific food items see Comprehensive Glycemic Index Chart and Glycemic Load Chart). Individuals should do their best to consume foods that provide low to medium GL foods in order to minimize rapid elevations in blood sugar levels.
A Specific Example:
Watermelon has a high Glycemic Index (72). As a result, one should be wary of watermelon. However, there are only a few grams of carbohydrates in a serving size; therefore, the Glycemic Load (4×72) of watermelon is relatively low. While watermelon may raise blood sugar levels quickly, the overall increase in blood sugar levels is low because there are so few grams of carbohydrates in each serving. This example shows both the benefits of the glycemic index and its limitations. It also shows why the glycemic load may be more practical.
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