The glycemic index is a relative measure of how dietary carbohydrates raise blood glucose. Carbohydrate sources that produce a high glycemic index value will have a high, rapid rise in blood glucose, and a rapid insulin response, after consumption. Sources include candy, soft drinks, raisins and a variety of breakfast cereals. On the other hand, carbohydrates producing a low glycemic index value have a low but prolonged rise in blood glucose and include items such as apples, bananas and milk.
Glycemic Index Calculation
Subjects fast overnight and are then given 50 g of carbohydrate, which is calculated based on the carbohydrate composition of the food of interest. You would need to consume roughly 218 g of cooked brown rice to get 50 g of carbohydrate. After consumption of the food of interest, blood glucose is monitored for two hours and the area under the two-hour blood glucose curve is compared to the area under the two-hour blood glucose curve of a 50 g dose of glucose only. Glycemic index values are expressed as a percentage ranging from 0 to 100, and are influenced by the type of starch, sugar content, fiber, cooking, food processing, acidity, fat and protein content, and the physical entrapment of bran.
Brown Rice
Brown rice produces a glycemic index value of 72, compared to glucose. Foods are categorized by the glycemic index as being within the low range of 0 to 55, moderate range of 56 to 69 or high range of 70 or greater. While this is a high glycemic index food, it is on the low end of the scale and most strains of rice have a glycemic index value in the range of 80 to 120.
Parboiled Rice
Parboiled rice produces a glycemic index value of 103, compared to glucose. Parboiled rice is right in the middle of the range of typical rice glycemic index, but it is significantly higher than that of brown rice. The choice of rice, and all of your food choices, can have an effect on your blood glucose, type 2 diabetes risk and other downstream metabolic events.
Glycemic Load
Glycemic load takes into account both the glycemic index and the amount of food consumed. The glycemic load aims to predict the blood glucose response of a specific type and amount of food, while the glycemic index offers a relative ranking of foods based on their blood glucose response. Benefits of consuming a low glycemic index diet include lower blood glucose levels, reduced cholesterol, a reduced risk of both type 2 diabetes mellitus and heart disease.
References
- "U.S. Department of Agriculture ARS"; USDA National Nutrient Database for Standard Reference, Release 23; December 2010
- "American Journal of Clinical Nutrition"; Glycemic Index of Foods: A Physiological Basis for Carbohydrate Exchange; Jenkins DJ, et al.; March 1981
- "American Journal of Clinical Nutrition"; International Table of Glycemic Index and Glycemic Load Values: 2002; Foster-Powell K, et al.; July 2002
