The Low Glycemic Index Diet - Ranking System

What is the Glycemic Index and why is it important to a Low Glycemic Index Diet?

Glycemic index (also glycaemic index, GI) is a ranking system for a low glycemic index diet. It ranks carbohydrates based on their effect on blood glucose levels. It compares available carbohydrates gram for gram in individual foods, providing a numerical, evidence-based index of postprandial (post-meal) glycemia. The concept was invented by Dr. David J. Jenkins and colleagues in 1981 at the University of Toronto.

Carbohydrates that break down rapidly during digestion have the highest glycemic rank. Carbohydrates that break down slowly, releasing glucose gradually into the blood stream, have a low glycemic index.

A lower glycemic index suggests slower rates of digestion and absorption of the sugars and starches in the foods and may also indicate greater extraction from the liver and periphery of the products of carbohydrate digestion.

A lower glycemic response is often thought to equate to a lower insulin demand, better long-term blood glucose control and a reduction in blood lipids. The insulin index may therefore also be useful as it provides a direct measure of the insulin response to a food.

The Glycemic Load (GL) is a ranking system for carbohydrate content in food portions based on their glycemic index (GI) AND the portion size.

The usefulness of glycemic load is based on the idea that a high glycemic index food consumed in small quantities would give the same effect as larger quantities of a low glycemic index food on blood sugar.

For example, white rice is somewhat high GI, so eating 50g of white rice at one sitting would give a particular glucose curve in the blood, while 25g would give the same curve but half the height. Since the peak height is probably the most important parameter, multiplying the amount of carbohydrates in a food serving by the glycemic index gives an idea of how much effect an actual portion of food has on blood sugar level.