The glycemic index (GI) measures only how quickly a particular carbohydrate turns into glucose (blood sugar) in the body. It does not show how much of the carbohydrate is in a certain food, or the influence on glucose of a variety of foods consumed in a single meal. Some foods have high-GI carbohydrate but do not have a great deal of it. It is important to know both of these factors:

• How much carbohydrate is in a food
• How quickly it converts into glucose

The glycemic load (GL) calculates this information to more clearly determine the effect of food on blood glucose. The glycemic load of food is calculated using the following formula:

• Take the available amount of carbohydrates in a serving of food (total carbs minus fiber).
• Multiply that number by the food’s GI.
• Divide by 100 for glycemic load.

For a half-cup serving of carrots, the GL would be calculated as:

8 (grams of carbohydrates) X 131 (GI) = 1048 / 100 = 10.4.

For a half-cup serving of white rice, the GL would be calculated as:

35 (grams of carbohydrates) X 81 (GI) = 2835 / 100 = 28.3.

Based on these calculations, if people chose foods using only the glycemic index, they might avoid some nutritious items. The carrots have a higher GI than rice but are actually better for the individual. This comparison demonstrates the importance of using the glycemic load rather than just the glycemic index in choosing food. A lower glycemic load means fewer carbohydrates and more nutrients and fiber. In general, foods with a lower glycemic load provide a better diet.

Glycemic Index vs. Glycemic Load
Table of Common Foods

Ranges for GI and GL

Calculating the GL is time-consuming and not always easy. It may be difficult to determine how many carbohydrates are in a serving of food or if that number changes in preparation and in combination with other foods, such as protein. This is another reason use of the glycemic index is viewed with caution when dealing with people with diabetes and why people with diabetes should consult a registered dietitian for nutrition counseling.