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What is the Glycemic Index?

The glycemic index (GI) gives rankings of food based on how fast a particular food is likely to raise blood glucose (blood sugar) levels in the human body. The numbers on the glycemic index are based on the glucose (the fastest carb next to maltose) value of 100 with other carbohydrate foods assigned numbers relative to glucose. Carbohydrate foods that assimilate rapidly during digestion have the highest glycemic indexes, as their blood sugar response is fast and high. Conversely, carbohydrate foods that assimilate slowly, gradually releasing glucose into the blood stream, have low glycemic indexes.

Calculating the GI of foods

Most of us eat meals comprised of foods that contain varying carbohydrate amounts along with fat, fiber, protein, and other nutrients. The glycemic index of a meal will show the GI of each carbohydrate food in the meal, as well as their proportional contribution to the meal’s total carbohydrate. The GI only applies to the carbohydrate servings in a meal, but even if the servings are comprised of different foods, the glycemic index of the entire meal can be easily calculated using the following steps:

1. Determine the amount of carbohydrates in each food.

2. Add the total carbohydrate grams.

3. Find the percentage of the total carbohydrate grams  

    contributed by each food.

4. Multiply that percentage by the food’s GI.

Example:

Your breakfast includes a bowl of whole grain cereal with fat free milk.

1. whole grain cereal = 23g + fat free milk = 13g

2. 23 + 13 = 36

3. 23 ÷ 36 = 64% (cereal); 13 ÷ 36 = 36% (milk)

4. 54 x .64 = 35 (cereal’s GI); 32 x .36 = 12 (milk’s GI)

It is important to know that if the only carbohydrate in a meal has a high GI, the total GI for the whole meal is high. However, by including a low GI food along with the high GI food, the effect on a meal may be favorably balanced.

 Why Know the GI of Carbohydrate Foods?

Low GI Foods:

   • Provide a slower, gradual rise in blood glucose

   • Can help to control diabetes

   • Can help to improve sensitivity to insulin

   • Can help with weight loss

High GI Foods:

   • Can raise blood glucose levels following a brief period of

     intense exercise

Make the Switch!

   • Whole or cracked grain breads instead of white or

      whole-wheat breads

   • Firmer cooked pasta instead of longer cooked, limp pasta

   • Basmati or converted rice instead of sticky or regular white

      rice

   • New potatoes instead of large, fluffy baking potatoes

   • Avoid foods and beverages with high-fructose corn syrup

   • Avoid pure, granulated fructose as a table sugar substitute

Glycemic Index Ranges (glucose = 100)

   Low-GI Foods               (below 55)

   Intermediate-GI Foods   (between 55 and 70)

   High-GI Foods              (more than 70)