Anyone who has diabetes, or has simply tried to cut back on his or her sugar consumption, will likely be familiar with the term “glycemic index”.
When choosing food, many individuals rely on the glycemic index (GI) to tell them exactly how much sugar will be absorbed by the body in the form of glucose. That is, in essence, what the glycemic index is: a rating of how fast the sugar from carbohydrates will enter the body.
Glycemic Load is a similar concept, but it makes an adjustment for the sugar content of the food in question. Glycemic load is generally considered to be the more useful of the two, however in this article I will explain both of them, and the differences that exist between them.
Why Do We Need To Know About Glucose Absorption?
When the body absorbs glucose, our blood sugar levels rise. In order to counteract this effect, the body starts producing insulin. Insulin is a hormone produced by the pancreas to regulate the metabolism of fat and carbohydrates. It forces the cells, primarily located in the liver and fatty tissue, to absorb glucose from the blood. This glucose is then converted into fat, and stored in the body to be used at a later date.
The more glucose is converted, the more weight the body gains in the form of fat.
This is obviously an undesirable effect for people on diets, but high levels of insulin can have even more drastic effects.
When blood sugar levels spike suddenly, a great release of insulin is triggered in the body. This in turn, and just as suddenly, drops blood sugar levels to below normal. This is what causes the sudden surge of energy followed by a severe depletion of energy compounded with hunger, commonly referred to as a “sugar rush”. Frequently subjecting the body to this treatment will result in weight gain, loss of energy and eventual development of type two diabetes.
How to Determine the Glycemic Index of Foods
In order to evaluate what the glycemic index of a particular food might be, a simple scale from zero to 100 is used, based on the effect of that food on blood sugar levels.
The higher the number, the greater the effect.
For easy interpretation, foods are categorized into three groups. A food with a low glycemic index would be anything below 56, a medium GI ranks between 56 and 70, while anything 71 or over is ranked as having a high GI. A recent Harvard Health Study lists both the GI and the GL for some of our most commonly eaten foods.
Studies that determine the glycemic index of foods require at least ten volunteers, although usually more are used in order to get more accurate results. The volunteers eat food containing a predetermined amount of carbohydrates. Usually 50 grams, or the equivalent of four tablespoons of sugar.
After eating, their blood sugar levels are measured over a period of two hours at set intervals, in order to see how their bodies respond. These results are compared against the same amount of pure glucose, generally in the form of table sugar, which would have a maximum glycemic index of 100.
Each person’s body is likely to respond differently to the food, so their blood sugar levels will not be equal. That is why a large number of volunteers is used. Their results are averaged in order to obtain an accurate glycemic index.
What Is the Glycemic Load?
Using only glycemic index to determine the glycemic effect that a certain food will have on the body does not provide an entirely accurate picture.
This is because the GI does not specify how much sugar there is in a particular food, but simply how fast it is absorbed by the body.
This is where the glycemic load (GL) comes in. In addition to measuring how fast the glucose enters the bloodstream, the GL also gives an idea of the sugar content in the food.
Knowing only how fast the sugar from carbohydrates is absorbed into the body is not enough to determine whether that type of food will cause elevated blood sugar levels. For example, there are many fruits and vegetables with a high glycemic index, meaning that the sugar enters the bloodstream very quickly. However, they have a very small amount of sugar to begin with, so this will not greatly impact blood sugar levels. Watermelon has a glycemic index of 72, which would rank it as high, but a glycemic load of only four, which is considered very low.
How to Determine the Glycemic Load of Foods
Measuring the glycemic load of a certain food involves a simple math calculation. It requires knowing the glycemic index of the food, and the grams of available carbohydrates in a portion.
The GI is multiplied by the number of grams, then divided by 100. The result is the glycemic load.
One important factor which exists here, and not for the glycemic index, is portion size. Regardless of the amount of a food that a person eats, the GI remains the same, but the GL will increase, since the number of carbohydrate grams also increases.
Fortunately, the glycemic load has become a standard form of measurement, so it is already specified on most food products, typically per 100 grams. As with the glycemic index, the GL is categorized as either low, medium or high. A GL of 10 or less is considered low, between 11 and 19 is medium and anything over 20 is high.
How To Use Glycemic Measures
Regulating and maintaining blood sugar can be useful in preventing a number of serious diseases, as illustrated by the Linus Pauling Institute at Oregon State University. These include type two diabetes, gall bladder disease, cardiovascular disease and obesity, which by itself brings on the risk of additional illnesses.
The Glycemic Index Foundation organized by the University of Sydney recommends a daily glycemic index of 100 stretched out across all meals.
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Apprentice Editor: Chrissy Tustison / Editor: Renee Picard
Photo: via Flickr