Carbohydrates and the Glycemic Index

Carbohydrates from food are split and transformed by the body into simple sugars such as fructose, glucose and galactose. Glucose is the sugar that is absorbed into the bloodstream.

The glycemic index is the rate of conversion of carbohydrate into glucose in the human body. It measures the speed with which a particular food is transformed into sugar that can be absorbed by the body. Foods are assigned a value ranging from 0 to 100 with the reference being pure glucose with a GI value of 100.

Low and High Glycemic Index

Some foods have carbohydrates that break down slowly and do not cause a drastic increase in the level of blood sugar. They are able to maintain the body's energy level to a significant extent due to the slow release of sugar into the bloodstream. A person feels full longer and craves for food less because the energy level is maintained. These low GI foods, with GI values not higher than 55, are called the "good carbohydrates."

Foods that are easily converted into glucose and cause a drastic increase in blood sugar level have GI values of 70 and above. High GI foods trigger the body to produce more insulin, the hormone that aids in converting glucose into stored fats. Because of the increase in insulin levels, a relatively high amount of sugar in the blood is immediately transformed and removed, leading to a drastic lowering of the blood sugar level, which manifests itself in lethargy and hunger. These foods cause the body to store fat and to experience hunger within a short period of time after eating. Hence, the term "bad carbohydrates."

Contributing Variables to a Food's Glycemic Index

Food processing significantly influences a food's glycemic index. Processing, like grinding and drying, removes a considerable amount of fiber in food. Fiber protects carbohydrates and slows down the actions of the digestive enzymes, which results in slower conversion of the carbohydrates into glucose. Processing starches also makes it easier for the body to digest and absorb them. Thirty grams of white bread has a glycemic index of 70, whereas 150 grams of steamed brown rice ranks low at 50.

Sugars in vegetables and fruits increase as they ripen, so the ripe ones usually have higher GI values. The kind of carbohydrates present in the food is also another factor. The more complex it is, the more difficult it is to digest and absorb. The acid and fat present in the food also affect their digestibility. The higher the acid and fat content, the slower the carbohydrate breakdown. Also, food that is finely ground is much easier to utilize compared to food that is coarsely ground.

The Glycemic Index as a Health Tool

Knowledge of the glycemic index is helpful in weight management. Foods with low GI values maintain the energy and sugar level of the body for a long period of time, which translates to feeling less hungry. This is crucial in losing or maintaining weight. High glycemic foods provide an immediate source of energy required after an intense physical exertion such as workouts and sports activities. However, low GI foods are required for physical exertions of long duration such as long exercise programs because they help in sustaining a constant energy level. The glycemic index is also utilized to prepare special diets for the diabetics.