According to the Merck Manuals Online Medical Library, the glycemic index of a carbohydrate is a measure of how fast the consumption of that carbohydrate increases plasma glucose levels. The index ranges from a value of 1, which is the slowest increase, to a value of 100, which is assigned to glucose itself and represents the fastest increase in plasma glucose levels. Carbohydrates with a "low" glycemic index, a value below 50, are the most healthful choices. Many variables influence the glycemic index of a carbohydrate.
The Extent of Cooking
Cooking time has an effect on the glycemic index of carbohydrates, explains the Penn Rodebaugh Diabetes Center. Carbohydrates swell and rupture, and the food becomes soft during prolonged cooking times. This makes the food more easily digestible so that glucose forms and get absorbs into the blood more quickly. Quicker absorption of glucose means a higher glycemic index.
Eating a Combination of Foods
According to the American Diabetes Association, the glycemic index of a particular carbohydrate varies depending upon whether it is eaten alone or in combination with other foods. It is possible to modulate the rapid increase in blood glucose brought about by a food that has a high glycemic index by consuming it with a food that has a low glycemic index. For example, the combination of a bagel, a food with a high glycemic index, with a glass of 1 percent milk, a food with a low glycemic index, will result in a slower increase in blood sugar relative to eating the bagel alone.
Fiber Content
The amount of soluble fiber in a carbohydrate affects its glycemic index because fiber retards the rate at which the carbohydrate is digested, explains HealthCastle.com. A slower rate of digestion means that the carbohydrate is converted to glucose more slowly, and this leads to a slower increase in blood glucose levels. The more soluble fiber the carbohydrate contains, the lower is its glycemic index.
Degree of Ripeness
The glycemic index of fruits and vegetables increases with the amount of time they are allowed to ripen.
Fat and Protein Content
The amount of fat and protein associated with a carbohydrate influences its glycemic index value. Fats and proteins slow down the digestion process. The higher the fat and protein content, the lower the glycemic index. Foods, like beans and milk, have a low glycemic index because the carbohydrates they contain are associated with fats and proteins.
