The glycemic index is a scale that rates how quickly a given carbohydrate causes blood sugar to rise. The faster that blood sugar rises, the faster that insulin is released. Insulin is a hormone that removes sugars from the blood. In general, refined carbohydrates, including sugars, rate much higher on the glycemic index than unprocessed complex carbohydrates, such as whole grains, fruit or vegetables.
The Glycemic Index Scale
The glycemic index can be broken down into three separate categories of "low," "medium" and "high," according to the American Diabetes Association. Foods that rank low on the glycemic index have a score of 55 or less; medium-ranking foods on the glycemic index rank between 56 and 69; and foods that have a ranking on the glycemic index rank 70 or higher. Examples of foods that rank low include most fruits, 100-percent stone-ground, whole-wheat bread, rolled or steel-cut oatmeal and legumes. Foods that rank medium on the GI include quick oats, rye bread, brown rice and couscous. Foods that rank high on the GI include white bread, white rice, rice cakes, popcorn, as well as macaroni and cheese.
Sugars and the Glycemic Index
Sucrose, also known as table sugar, has a glycemic index of 68, according to the Linus Pauling Institute. Glucose ranks at 96; fructose, 22; brown sugar, 64; agave syrup,15; maple syrup, 54; black strap molasses, 55 to 60; and honey, 60. Many other foods that contain little to no sugar, however, have a much higher glycemic index than pure sugar. You cannot guess or assume to know the glycemic index of a food, based on the amount of sugar it contains. For example, a baked potato has a glycemic index of 111, which is much higher than one name-brand candy bar, whose glycemic index is a mere 51, according to Harvard Medical School. Still, another fruit-flavored snack food, which contains processed forms of sugar, comes in at 99 on the GI scale.
GI Values of Sugary Foods
Foods that contain refined sugars can have unpredictable glycemic indexes. The Linus Pauling Institute notes that doughnuts rank at 76 and jellybeans at 78. On the other hand, banana cake made with sugar ranks at 47, while banana cake made without sugar ranks at 55, according to Harvard Medical School. One brand of soft drink has a glycemic index of 63, while a name-brand sports drink comes in at 78. While both of these beverages are made with refined sugar, the sports drink, which has the higher GI, actually has a lower sugar content.
Even though potatoes, pumpkins, parsnips and some other vegetables have a high glycemic index, you shouldn't avoid these foods, according to the University of Sydney. You shouldn't avoid these foods because they have a high micronutrient content and a medium glycemic load. The glycemic load of a food is the measure of the glycemic index multiplied by the total number of carbohydrate grams per serving. The result is divided by 100. Therefore, foods that may rank high on the glycemic index can have a relatively low glycemic load, as long as the number of carbohydrates per serving is small. By controlling your total carb intake, you can control your glycemic load and your blood sugar levels.