Simple and complex carbohydrates in the diet
Carbohydrates may be classified as simple carbohydrates or complex carbohydrates, depending on the number of simple sugars in the molecule. Carbohydrates containing one or two simple sugars like fructose or sucrose are termed simple carbohydrates, while starchy foods are categorized as complex carbohydrates because starch is made up of long chains of the simple sugar, glucose.
Glycemic index affected by chemical nature of the carbohydrates in the diet
Glucose is the body's preferred source of energy and the body processes glucose very efficiently. But the body has a limited capacity for handling fructose, a common monosaccharide in fruits and honey; this is why fructose has a low glycemic index of 23. Ordinary table sugar (sucrose) is a disaccharide made up of one molecule of glucose linked to one of fructose. This helps explain why the GI of white sugar is 65, almost midway between 23 and 100 in the intermediate range.
Glycemic index affected by physical nature of the carbohydrate in the diet
The precise physical nature of the carbohydrate in a particular food also affects the glycemic index value of that food. For example, most breads are in the high range - not due to the chemical nature of wheat starch, but for two mechanical reasons. The fine particle size of wheat flour gives digestive enzymes great surface area to attack. The puffed-out structure of bread also increases the surface area of the food. The higher glycemic index value of bread is partly the result of this typical physical structure of bread.