The rate of absorption of glucose appears to be important in controlling blood glucose, insulin release, obesity and possibly weight loss, according to Sareen Gropper, et al., in "Advanced Nutrition and Human Metabolism." White bread is often used as a standard against which to measure the rate at which foods provide glucose to the blood and stimulate insulin release.
Identification
The glycemic index classifies foods according to their potential for raising blood glucose. Glycemic index is the increase in blood glucose level over a baseline level during the two hours following consumption of a defined amount, usually 50 g, of carbohydrate compared with the same amount of carbohydrate in a reference food. The reference food, originally glucose but later white bread, is arbitrarily assigned a score of 100 and other foods are compared to this standard.
Function
The glycemic index ranks the effects of individual foods on blood glucose relative to a carbohydrate such as white bread. Diet plays an important role in improving insulin resistance, so this comparison allows people to choose foods that meet their nutritional needs without aggravating an impaired glucose response, if one exists.
Rankings
Foods are given an individual glycemic index number and groups of foods are categorized as high, medium or low GI. Foods with a high glycemic index include white bread, short-grain rice, corn flakes, waffles, potatoes, carrots, watermelon, jelly beans, soft drinks and honey.
Foods with a moderate or medium GI include sourdough or rye bread, shredded wheat, banana, pineapple, orange juice and ice cream. Foods with a low GI include pumpernickel bread, pasta, bran cereals, soybeans, lentils, baked beans, peaches, apples, oranges, milk, yogurt and chocolate, according to Eleanor Noss Whitney and Sharon Rady Rolfes in "Understanding Nutrition."
Significance
A defensive nutrition plan for blood glucose levels focuses on foods that supply glucose to the cells at a steady rate and make moderate insulin demands. The glycemic index allows you to plan meals incorporating foods that avoid too great a rise or too sudden a fall in blood glucose and insulin response. This is especially important to people with diabetes.
Considerations
If glucose is used as the reference food, white bread has a glycemic index of approximately 71. If white bread is used as the reference food, some foods will have a glycemic index greater than 100. Factors that influence the glycemic index include the amount and type of fiber, fat and sugar in the food and the starch structure of the carbohydrate in the food. Foods with soluble fiber tend to have a low glycemic index. Fructose causes less of an increase in blood glucose level than sucrose or glucose.
The relative high or low glycemic index of a food may not be intuitive. For instance, ice cream produces less of a glycemic response than a baked potato. Foods consumed together affect your glycemic response to the meal. Some people consider the glycemic index a practical way to improve glucose control, but others view it as too complicated to be useful.
References
- "Advanced Nutrition and Human Metabolism"; Sareen Gropper, Jack L. Smith and James L. Groff; 2009
- MayoClinic.com: Glycemic index diet: Losing weight with blood sugar control
- Linus Pauling Institute: Glycemic Index and Glycemic Load
- "Understanding Nutrition, Ninth Edition"; Eleanor Noss Whitney and Sharon Rady Rolfes; 2002
- "Krause's Food, Nutrition, & Diet Therapy, 10th Edition"; Mahan and Escott-Stump; 2000
