Glycemic index (GI) measures the rate at which sugars in food are released to the blood stream. Food stuffs including fruits, vegetables, and animal products, vary in the amount and composition of sugars (carbohydrates) they contain. This variation causes foods to have different glycemic index and glycemic load and therefore, variable effects on the sugar level in the blood stream.

Glycemic load =  0.01 X glycemic index X grams of carbohydrate consumed.

Not only does glycemic index of foods vary depending on the type of food category but also can also differ among different varietes of the same food type. For example, a study of the glycemic index of 235 rice varieties found that there is a significant difference in glycemic index among them, even though they all fall within the low-to-medium range. Generally brown rice has lower glycemic index than the polished white rice.

Foods containing carbohydrates that are released rapidly to the blood stream have high glycemic index, whereas foods that release carbohydrates slowly have low glycemic index.

Generally, foods with glycemic index of 55 or less are considered to be low in glycemic index; 56 – 69 as medium; and 70 and above as high.

High glycemic index foods are associated increased risks of type II diabetes. Therefore, nutritionists advise people at risk of developing diabetes or who want to manage it to make foods with low glycemic index as part of their strategy.

In the following tables are lists of common foods (fruits, vegetables, grain products, dairy products etc. ) and their glycemic index. The data was compiled by an Australian nutritionist Jennie Brand-Miller and her group based on analysis of glycemic index data published world-wide between 1981 – 2007. The values are based on glucose reference scale and averages ± standard error

 Glycemic Index of Grain and Grain Products

Table 1: Glycemic index (glucose reference scale) of grain and grain products.

High Carbohydrate foods Glycemic Index
White wheat bread 75 ± 2
Whole wheat/whole meal bread 74 ± 2
White rice, boiled 73 ± 4
Unleavend wheat bread 70 ± 5
Brown rice, boiled 68 ± 4
Couscous 65 ± 4
Wheat roti 62 ± 3
Udon noodles 55 ± 7
Rice noodles 53 ± 7
Speciality grain bread 53 ± 2
Sweet corn 52 ± 5
Chapatti 52 ± 4
Spaghetti, white 49 ± 2
Spaghetti, whole meal 48 ± 5
Corn tortilla 46 ± 4
Barley 28 ± 2
Breakfast cereals Glycemic Index
Cornflakes 81 ± 6
Instant oat porridge 79 ± 3
Rice porridge/congee 78 ± 9
Wheat flake biscuits 69 ± 2
Millet porridge 67 ± 5
Muesli 57 ± 2
Porridge, rolled oats 55 ± 2