The glycemic index
د. حسين محمد جمعهاختصاصي الامراض الباطنة
البورد العربي
كلية طب الموصل
2012
The glycemic index, glycaemic index, or GI is a measure of the effects of carbohydrates in food on blood sugar levels. It estimates how much each gram of available carbohydrate (total carbohydrate minus fiber) in a food raises a person's blood glucose level following consumption of the food, relative to consumption of glucose. Glucose has a glycemic index of 100, by definition, and other foods have a lower glycemic index.
Foods with carbohydrates that break down quickly during digestion and release glucose rapidly into the bloodstream tend to have a high GI; foods with carbohydrates that break down more slowly, releasing glucose more gradually into the bloodstream, tend to have a low GI.
Classification
GI rangeExamples
Low GI
55 or less
most fruits and vegetables, legumes/pulses, some whole, intact grains, nuts, fructose, kidney beans, beets, chick peas
Medium GI
56–69
whole wheat products, basmati rice, sweet potato, sucrose, baked potatoes
High GI
70 and above
white bread, most white rices, corn flakes, extruded breakfast cereals, glucose, maltose, maltodextrins
Slow acting carbohydrates will also reduce the peaks in blood glucose that often follow a meal, and this may have a role in helping to prevent or reduce the risk of getting Type 2 diabetes in those at risk.
There are also benefits for weight loss. Low GI foods can help you to control your appetite by making you feel fuller for longer, with the result that you eat less.
Research has shown that people who have an overall low GI diet have a lower incidence of heart disease.
Lower GI diets have also been associated with improved levels of 'good' cholesterol. One or two small changes can make all the difference.
Does anything else affect GI?
Yes. Determining the GI of a meal is not so easy as reading a number off a chart. The addition of fat and protein slows down the absorption of carbohydrate. Chocolate has a medium GI because of its fat content therefore, and crisps and chips will actually have a lower GI than potatoes cooked without fat. Milk and other dairy products have a low GI because of their high protein content, and the fact they contain fat.The consequence of this is that if people were to confine themselves to low GI foods, their diet would be unbalanced and high in fat, which could lead to weight gain and increase their risk of heart disease. For this reason it is important not to focus exclusively on GI and to think as well about the overall balance of the diet.
