How Foods Rank by Glycemic Index

Glycemic index refers to relative ranking of carbohydrates, compared to glucose, based on their ability to raise the blood glucose level after consumption. Glycemic index is a relative scale and not dependent on the amount of food consumed. Glucose is assigned a glycemic index value of 100 and rest all foods are compared against this reference value. Almost all foods will have index value below 100.

For better understanding, consider the following hypothetical example in which on one morning after an overnight fast, a person consumes 50 g of glucose and the next morning after an overnight fast, he consumes some other food with 50 g of carbohydrates. The effect of the two on blood glucose levels will be different. This difference arises because of different rate of digestion and absorption of different foods. Glucose, which has a very high index, is rapidly absorbed (no digestion needed) and results in a rapid increase in blood glucose level, and the peak value is also higher. However foods with low index are slowly digested and absorbed, thus producing a gradual but prolonged rise in blood glucose levels, and the peak value of blood glucose is also lower in this case.

So why to bother with glycemic index if one consumes equal amount of any food, thus providing with the same amount of total calories? It is important because foods with lower index have proven health benefits. Diet containing higher percentage of low index foods improves both glucose and lipid levels in the blood. They also aid in weight control by controlling appetite as they increase blood glucose levels for a longer period of time. Recent studies also indicate that they reduce the risk of type 2 diabetes mellitus, coronary heart disease and obesity.

The foods are classified as having a high index when their glycemic index value is 70 or above. Examples include white bread, glucose, fruits like dates and watermelons, white rice, etc. Medium index is defined as the glycemic index from 56 to 69. Foods having a medium index are whole-wheat products, fruits like peaches, raw apricots, papayas and pineapple, basmati rice, sweet potato etc. Foods with glycemic index value of 55 or less are classified as low glycemic index foods. Most of the fruits and vegetables are included in this category. Also included are dairy products like milk and yogurt (without added sugar), legumes and pulses, nuts, most of the beans like white beans, soy beans, red kidney beans, etc.