Glycemic Index

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The glycemic index or GI is a measure of the effects of carbohydrates on blood sugar levels. Carbohydrates that break down quickly during digestion and release glucose rapidly into the bloodstream have a high GI; carbohydrates that break down more slowly, releasing glucose more gradually into the bloodstream, have a low GI.

The concept was developed by Dr. David J. Jenkins and colleagues  in 1980 at the University of Toronto in their research to find out which foods were best for people with diabetes.

A lower glycemic index suggests slower rates of digestion and more efficient absorption of the foods’ carbohydrates. A lower glycemic response usually equates to a lower insulin demand but not always. Insulin is the body’s response to sugar. It is a hormone that instructs cells to stop burning fat or protein and absorb only carbohydrates. When blood sugar is low the body sends hunger messages.

Low GI (55 or less) foods include most fruits and vegetables, legumes, whole grains, nuts, and fructose.  Medium GI (56–69) include whole wheat products, basmati rice, sweet potato, and sucrose (table sugar). High GI (70 and above) foods include baked potatoes, watermelon, white bread, most white rices, corn flakes, and glucose (blood sugar).

The glycemic index does not, however take into account other factors besides glycemic response, such as insulin response, which is measured by the insulin index and can be more appropriate in representing the effects from some food contents other than carbohydrates. It is also significantly altered by the type of food, its ripeness, processing, the length of storage, cooking methods, and its variety (white potatoes are a notable example, ranging from moderate to very high GI even within the same variety).

The glycemic index is useful, but simply decreasing carbohydrate intake is still a far more effective way to regulate blood sugar.

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