Diabetics should try to plan their meals so that they avoid "spikes" in their blood glucose levels. GI can be a useful tool to help keep blood sugar levels stable throughout the day.
The GI of a food is usually determined by having one or more persons eating a specified amount of a single food and then measuring the change in blood sugar levels after these people have eaten a control food. The average change in the blood sugar levels over a certain amount of time, relative to the levels after the consumption of the controlled food, is known as the glycemic index. The lower the GI number, the less effect the food has on your blood glucose levels in the 2 or 3 hours after you eat.
All foods that have carbohydrates raise or maintain blood sugar levels to a certain extent. High-fat as well as high-fiber foods tend to have a much lower GI because people must eat larger amounts of digestible carbohydrate. Both the fiber and fat in these foods can slow the rate of gastric emptying and will, therefore, slow the rate of delivery of carbohydrates to the small intestine where it is digested and glucose is absorbed. Fats delay your stomach from emptying, and the fibers may increase the viscosity in order to slow down the rate.
The GI is used mainly as a scientific research tool. It may be hard to use the GI as a measure on which to base the dietary recommendation for the general population, because of the wide variability depends on the ripeness of a food, the degree in which a certain food may be cooked as well as other factors.
That said, the glycemic index can be used as a reference tool for people trying to choose foods that have a lower impact on their glucose levels.
The GI is all about high carbohydrate foods. Foods that are high in fat or protein (typically low-GI foods) do not cause your blood glucose levels to rise very high. On the other hand, foods high in carbohydrates (typically high-GI foods) can cause blood glucose levels to rise quickly.
Many people think that diabetics have to limit their quantity of plain table sugar, when, in actuality, a baked potato can be even worse. Use of the glycemic index to help with meal preparation can help you to keep your blood glucose levels under control. Regular exercise is also an important part of managing diabetes.
A properly planned GI diet may help some people manage type 2 diabetes (ask your doctor for advice). Lists of low-GI foods and recipes are available. The glycemic index of individual foods is not as important as the overall GI of your entire meal. And remember, you can still enjoy desserts -- just with a little extra planning!