Glycemic Index
Glycemic index (GI) is a scale from 0 to 100, which describes how a food affects blood sugar, when eaten alone. Lower numbers correspond to foods that enter the blood stream slowly and have a sustained effect on blood glucose levels. Foods with a high glycemic index can cause rapid spikes in blood sugar. When these large spikes occur repeatedly, the body has difficulty regulating serum glucose, which is especially problematic in a person with diabetes mellitus or insulin sensitivity. Diets with excessive high GI foods are also linked to increase risk of obesity and heart disease.
Glycemic index is affected by several factors:
Processing: In general, whole grains have a lower GI than refined grains and coarsely ground grains have a lower GI than finely ground grains.
Cooking: Overcooked pasta has a higher GI compared to al-dente pasta.
Ripeness: GI tends to increases with the ripeness of the fruit or vegetable.
Fiber content: Fiber is not digestible, so the higher the fiber content of a food, the fewer sugars it can release into the blood stream.
Fat and acid content: Carbohydrates are converted to glucose more slowly in the presence of fat and acid.
Glycemic Load
In a practical sense, glycemic index is not very useful since it does not consider serving size. Glycemic load (GL) similarly describes the glycemic response of a food, but also considers the amount of carbohydrates in an average serving size and is, therefore, more useful.
GL = GI/100 * (grams of carbohydrates per serving)
See Table 2 below for examples of glycemic index and glycemic load for common foods.
Table 2: Glycemic index and load of common foods (4)
Interpreting the Numbers: