The Glycemic Index, or GI, is a ranking given to foods that contain carbohydrates. It measures their effect on blood sugar. Carbohydrates that digest more rapidly are converted more quickly into blood glucose, and therefore have a higher ranking on the GI scale. The American Diabetes Association does not recommend replacing a food's GI measurement as a primary tool to manage diabetes. Instead it states that it is useful when used in conjunction with carbohydrate counting as a way to keep blood sugar under control.
What affects the GI of a food?
A lot of factors go into measuring a food's glycemic index. Foods that contain more fat, fiber, and protein tend to have a lower GI rating because they are digested and released into the blood stream more slowly. Ripeness and storage time of fruits and vegetables also has an effect. In general, the riper it is, the higher the GI. Cooking also impacts a food's ability to raise blood sugar, as heating changes its chemical structure.
Dates actually have the highest GI rating. They fall outside of the normal range of the glycemic index, which is 0 to 100, and rank at a whopping 103. Fruits that are dried, such as dates and raisins, are often high in simple sugars, which make them raise blood sugar more rapidly.
A plain baked potato cooked in a microwave oven has a GI of 85. This causes many dieters and diabetics to shy away from this nutritious vegetable. However, a standard baked potato has only 132 calories, and if eaten with the skin on, contains almost three grams of fiber. The type of potato chosen has an effect on its glycemic index as well. A red new potato, for example, has a GI of 57, and may be a better choice for those having trouble controlling blood-sugar levels.
One may expect snacks such as potato and corn chips to rank higher than 75 on the glycemic index. The reason that they do not is often because of their fat content. Potatoes that are fried in oil are digested more slowly than a plain potato that is cooked without added ingredients. This does not, however, make the food better for you. In fact, a serving of potato chips is higher in calories than a serving of plain potatos, which has an effect on blood sugar because of the increased energy load presented to the body.
White bread is the food with the worst reputation in the grain world. Its glycemic index of 77 does not make it the highest ranked food on the scale, but overall it is lower in most nutrients than other types of grains. Whole-wheat bread is higher in fiber and contains more vitamins B6 and E, magnesium, zinc, and folic acid. And don’t mistake white-wheat bread as a better alternative. White wheat is actually made from a whole grain that is lighter in color, milder in flavor and higher in fiber than standard wheat flour that has been refined to produce white breads.