Glycemic index (GI) is one of several metrics used to quantify short-term changes in blood glucose levels in humans following the ingestion of carbohydrate-containing foods. Glucose is the body's source of energy; it is the fuel used by the brain, muscles, and other organs. Glucose is set at 100, and all foods are indexed against that number. Therefore, foods that are quickly digested have a high G.I., and foods that are digested more slowly have a lower G.I.
One example of a low-glycemic diet is the Glycemic Index Diet developed by David J. Jenkins, a professor of nutrition at the University of Toronto and later turned into a successful line of diet books by author and former president of the Heart and Stroke Foundation of Ontario, Rick Gallop.
Examples of G.I. ratings
- Any food rating less than 55 in the G.I. is considered low
Use of the G.I.
The glycemic index is a useful aid for diabetics and other people who wish to control their blood glucose levels. A diet based on foods with low glycemic response has been associated with diabetes management, improved blood lipids (cholesterol), reduced risk of heart disease, and weight management[unreliable source?]. Not only will foods with a low glycemic index take longer to digest (therefore prolonging satiety) they will also maintain blood glucose levels at a relatively constant state. Foods with a high glycemic index not only digest quickly, but they also can cause extreme fluctuations in blood glucose.
There are some specific factors to consider in foods that can indicate their glycemic index: Low glycemic foods contain fat, protein, fiber, whole grains, raw starches, legumes, vegetables, fruits and dairy products. High glycemic foods contain refined grains, refined sugars, and increased amylopectin/amylose ratio.
There are other factors that contribute to a food's glycemic index, such as plant variety, ripeness, food processing, cooking method, and the other foods served with it.
There are criticisms of the glycemic index, including how impractical it is. The preparation and combination with other foods can alter its glycemic index. There is no requirement to display the glycemic index of a food product, and it is not always easy to predict the glycemic index of certain foods. Switching from a high glycemic index diet to a low glycemic index diet can be made relatively easy. Switching white bread and pastas to whole grain, eating breakfast cereals from oats, bran or barley, adding more fruits and vegetables when cooking, and reducing potato consumption can all aid in lowering glycemic index.
- Gallop,R: The G.I. Diet Express For Busy People (Virgin Books Ltd, 2007), page 10
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- Whitney, Eleanor Noss, and Sharon Rady Rolfes. Understanding Nutrition. Belmont, CA: Wadsworth, 2002. ISBN 978-0534590048