Periodic Table -> Glycemic Index

Glycemic Index

The glycemic index or GI is a measurement of the effects of different carbohydrates on our levels of blood glucose. Since all carbohydrates are not created equal, their effects in our bodies also vary. The glycemic index ranks carbohydrates in accordance with their effects on our blood sugar levels. Consuming foods containing less glycemic index carbohydrates means, choosing those which give rise to very less variation in our insulin and blood glucose levels. This is the way to maintain good health and lessening the risk of diabetes and other weight related problems. Dr. David J. Jenkins along with his colleagues in the year 1980 – 1981 first developed this concept at the University of Toronto.

Significance of High GI and Low GI

Carbohydrates breaking down fast during digestion and releasing glucose quickly into our bloodstream possess a high GI. On the other hand, carbohydrates prone to breaking down more slowly and thus releasing glucose gradually in the bloodstream contain low GI. A lower level glycemic index signifies slower pace of digestion as well as absorption of the carbohydrates in the foods. This also means higher extraction out of the liver of the products related to carbohydrate digestion. A lower GI also generally amounts to lower demand of insulin, and may contribute to improving blood lipids and blood glucose control, though not every time.

Meaning of the GI of a Food

The measurement of the GI of foods is done using scientific methods. Presently there are a few nutritional research groups throughout the world who give a legitimate testing. This is how GI values are measured in the Human Nutrition Unit, Sydney University.

Ten or more normal, healthy individuals are fed with a part of food which has 50 grams of digestible carbohydrates. The effect is measured on their bloodstreams in the subsequent two hours. For each individual, the area below their two hours response of blood glucose (glucose AUC) for that particular food is measured. On a different occasion, those original ten people are made to take in an equal amount of carbohydrate of glucose sugar (which is the standard reference). Again after two hours, their response relating to blood glucose is measured. The GI value of the specific food is calculated for each individual in the following manner. Each person’s glucose AUC for the food to be tested is divided by his glucose AUC for the standard reference food. The test food’s final GI is found out by averaging the GI value of the ten individuals.

Glycemic Index of Certain Foods

Most of the vegetables and fruits with the exceptions of potatoes and watermelon have low GI. The range of GI is less than 55, taking into account glucose’s glycemic index at 100. Other food products in the low GI category are grainy breads, legumes, pulses, milk products and brown rice.

Sweet potato, table sugar, basmati rice, whole wheat products have medium GI ranging from 56 to 69.

The high GI category food products include rice krispies, corn flakes, baked potatoes, and white bread. These foods have GI of 70 and above.

The GI effect of foods is dependent on a whole lot of factors like the kind of starch, whether it is amylose or amylopectin, the entrapment of starch molecules in the food, the food’s protein and fat content. It is also dependent on the presence of organic acids and salts. Addition of vinegar, for instance will reduce the GI. Fat and dissolvable dietary fiber lower the pace of gastric emptying, thus reducing the GI.

Benefits of Using the Glycemic Index

Consuming foods with high GI can pose a threat to the health as your body is pushed to the extremes. A sedentary lifestyle along with obesity adds to the risk factors. Switching to intake of low GI carbohydrates brings with it a sense of fullness for a longer period reducing hunger pangs. This is associated with a lot of health benefits like weight control, better diabetes management, and prevention of heart diseases.

The ideal technique for consuming foods with low GI is swapping high level GI carbohydrates for low GI carbohydrates. Eating whole grained bread, vegetables, and fruits along with cutting down potatoes or other foods with high GI is the solution.