GLYCEMIC INDEX EXPLAINED
Written by guest author Nynke Burggraaff
I'm sure you've heard a buzz going around about the glycemic index. A lot of people are adjusting their food intake according to low Glycemic Index (GI) values. But what exactly is the glycemic index?
The glycemic index (GI) provides an estimate for the rate at which your blood sugar rises after you've eaten carbs. Carbs that break down quickly during digestion and release glucose rapidly into the bloodstream have a high glycemic index (sugar), while carbs that break down slowly and gradually have a low glycemic index (oatmeal).
The glycemic index of two products with the same amount of carbs can vary. For instance white rice and brown rice have the same amount of carbs but the brown rice releases the glucose from the carbs slower than the white rice releases the glucose. This is what they mean by slow and fast carbs.
Determining the glycemic index
The glycemic index ranks from 0 to 100. The way the glycemic index of one product is determined is by experiment. A number of 10 or more people are given certain amount (mostly 50 grams) of pure glucose (sugar). The speed of the increase of their blood sugar level is then measured and this is equated with the number 100. This same test is repeated with other foods.
The values of the glucose of different foods are placed in the glycemic index. The index expresses the increase of the blood sugar level in relation to the increase that the glucose causes. So the faster the consumption of those foods leads to increasing of the blood sugar level which results in a higher glycemic index value. Below you can see what the numbers mean.
|Low GI||55 or less|
|High GI||70 and above|
The glycemic load (GL) is based on the same values of the GI but gives a more complete overview since it incorporates portion size. Obviously, a small portion fries has a different effect than a large portion fries!
The GL is easier to calculate since it does not depend on human trials. In order to calculate the GL, you should know the GI and the amount of carbs in your food. To find out the amount of carbs just check the packaging labels or use the nutrition guide.
The calculation is as follows:
Gl x Grams of carbohydrates / 100
For instance we want to know the GL of a cup of lima beans. First we have to know what the GI of beans is, this is 32. Now we need to figure out how many grams of carbs are in one cup of lima beans. This is, coincidentally also 32. The calculation thus goes as follows:
32 (GI) x 32 =1024 /100 = GL 10.24
Here's what the GL numbers mean.
|Low||10 or less|
|Medium||11 - 19|
|High||20 and above|
It is very easy to find the GI's and even the GL's of many foods from online websites; however, you should remain cautious about which information sources you use. I prefer to use sources like the American Diabetes Organization or other respectable websites.
Below you'll find a short list of foods and their GI from the American Diabetes Organization just to have a better understanding of the GI concept.
Low GI Foods (55 or less)
100% stone-ground whole wheat or pumpernickel bread
Oatmeal (rolled or steel-cut), oat bran, muesli
Pasta, converted rice, barley, bulgar
Sweet potato, corn, yam, lima/butter beans, peas, legumes and lentils
Most fruits, non-starchy vegetables and carrots
Medium GI (56-69)
Whole wheat, rye and pita bread
Brown, wild or basmati rice, couscous
High GI (70 or more)
White bread or bagel
Corn flakes, puffed rice, bran flakes, instant oatmeal
Shortgrain white rice, rice pasta, macaroni and cheese from mix
Russet potato, pumpkin
Pretzels, rice cakes, popcorn, saltine crackers
melons and pineapple
The GI and the GL are instruments that are very useful for people who have to monitor their blood sugar level such as those with diabetes. People who are watching their weight can also benefit from these instruments even though a lot of it boils down to common sense. For example, most people know that whole wheat is better than white bread but it never hurts to check the GI's of your favorite foods.