The body converts all carbohydrates into glucose (blood sugar), which is burned for energy or stored in the body. In the theory of the glycemic index, the faster the carbohydrates are broken down by the digestive system, the faster they travel to the blood and the quicker the glucose rises.

The increased glucose in the bloodstream causes greater production of insulin, which may over time stress the pancreas, and a person with diabetes must handle the extra glucose in the body. The rapid rise in glucose (hyperglycemia) may result in a burst of energy quickly followed by hypoglycemia and hunger. This cycle is not considered healthy.

Examples of high-glycemic foods with a GI over 70 include:

• White bread
• White potatoes
• Some cereals
• Snacks such as corn chips, potato chips and pretzels
• Honey and jams

Although high-glycemic foods may be considered the “bad” carbohydrates, some of the foods are valuable in the diet. People with diabetes need not abstain from high-GI foods. Instead, they are advised to consider high-GI foods that are more nutritious and lower in calories. For example, a high-fiber cereal may have a GI index of 80. However, it provides more nutrients than corn chips, which have a GI of 72.

Some carbohydrates cause a rise in glucose that is not as dramatic as with the high-glycemic foods. These foods are categorized as having an intermediate/moderate glycemic index. The GI for this category is 55 to 70 and includes:

• Some cereals
• White and brown rice
• Crackers and whole-grain breads
• Canned fruits
• Table sugar

Along with the high-GI foods, it is important for people with diabetes to realize that the foods in this category are not all the same. Some foods should be eaten sparingly as they have the same GI but little nutritional value. Table sugar and beets both have a GI of 65, but beets contain far more nutrients.

The food that produces the most gradual rise in glucose is placed in the low-glycemic group. These foods are considered the easiest on the body and may control hunger for a longer period of time. Foods with a GI lower than 55 include:

• Green vegetables
• Most fresh fruit
• Whole grains and beans
• Some fruit juices

In general, the low-glycemic carbohydrate foods are lower in fat and higher in fiber. There are still some foods in this category that contain empty calories. Peanut candies and frozen lima beans have the same GI of 32, but the lima beans are more beneficial in nutrients and fiber.

Using the glycemic index can be complicated and confusing. In addition to checking the GI value, the individual must consider the type of food, its nutrients and the overall diet. There are several factors beyond just the GI number that influence the effect of foods on glucose. These factors include:

• Region where an individual lives. For example, foods are processed differently in different parts of the United States, and an item such as rice can be grown in many ways depending on which part of the world the rice is coming from.
  
  
• The way the food is prepared (e.g., cooked, chopped, mashed).
  
  
• How it combines with other food (e.g., the protein and fat–containing food in a meal).
  
  
• The type of carbohydrate in the food.
  
  
• The amount of processing the food item has undergone.
  
  
• The ripeness of the fruit or vegetable.
  
  
• Fiber, fat and protein content of the food.
  
  
• The individual’s glucose level before eating.
  
  
• How quickly the body digests food (this varies from person to person).
  
  
• The individual’s activity level.

Knowing the general glycemic index of foods is therefore not enough information to plan a safe diabetic diet.