The glycemic index, or GI, is an index used to measure how much blood glucose spikes after eating a particular food. After each meal, carbohydrates are broken down, digested and absorbed, and then transported as glucose into the blood. The blood, with the help of insulin, then transports glucose into all the tissues of the body to be used as energy. Foods that have a high GI are usually digested and absorbed quickly, which in turn causes the glucose to enter the blood fast and causes a dramatic rise in blood glucose. On the other hand, those with a low GI take longer to process, causing a more gradual and less spiked rise of blood glucose.
Barley
The glycemic index of barley depends on how it is processed. It can vary from 25 for pearl barley, 50 for cracked barley and 66 for flaked barley. Thus, barley is a moderate-GI grain, and eating it results in a moderate rise in blood sugar.
Corn
Corn is one of the three main grain crops in the United States. The glycemic index of corn is around 80, which makes it a high-GI food. This means that corn, by itself, will cause a steep rise in blood glucose.
Oats
The GI of oats, another very important grain crop, also varies depending on how it is prepared, ranging from 66 for oat-bran bread, 80 for cooked oatmeal, 91 for oat bread, and 92 for one-minute instant oats. So, blood glucose will rise depending on what type of oats you eat and what you mix them with.
Rice
Rice is one of the most important staples in the world. There are many types of rice and many ways to prepare it. Thus, the GI in rice varies substantially depending on what type it is -- long grain, wild or white -- and how it is prepared: boiled, steamed or fried. Rice's GI ranges from 50 to 81. However, in general, the less processed the grain is, the lower GI it will have.
Glycemic Index of Rye
Rye usually has a relatively low GI, ranging from 35 to 45. However, be aware that rye bread, which is 80 percent rye kernels and 20 percent white wheat flour has a GI of 70.
Glycemic Index of Wheat
Wheat, another very popular grain, has a relatively low GI. Wheat kernels have a GI of 45, and pasta's GI usually ranges from 55 to 65. However, whenever a grain is highly processed, as is the case with white bread or gluten-free treated bread, GI increases substantially. White bread has a GI of 100.
References
- "Nutrition Therapy and Pathophysiology"; Nelms, Sucher, and Long; 2007
- The Glycemic Index
