Foods that contain carbohydrates can be ranked according to how quickly and how high they raise the body's blood sugar levels. Glycemic index, or GI, rankings are often used as a meal planning guideline by diabetics as well as people following a low-carb diet. However, many are unaware of exactly what affects a food's GI.
Definition
A food's glycemic index refers to its effect on blood sugar levels when compared with a carb-rich baseline, such as glucose or white bread. High GI foods cause blood sugar to increase more than low GI foods, and vice versa. Glycemic index only rates foods that contain carbohydrates. Foods that contain no carbs, such as meat and fish, cannot be rated on the GI scale.
Diabetes and Glycemic Index
Because it rates food's effects on blood sugar levels, diabetics are often the first population that comes to mind when considering the glycemic index. However, the jury is still out on whether or not diabetics get much benefit from using glycemic index as a guideline. The "American Journal of Clinical Nutrition" reports that the GI is a useful tool for predicting blood sugar levels, but it can potentially lead to diets higher in unhealthy foods such as those containing saturated fats. Furthermore, the American Diabetes Association, or ADA, recommends diabetics use glycemic index less as a menu planner and more as a guideline. In addition, the ADA recommends that diabetics also continue to count carbs and consider portion sizes.
Foods With Low GI
Foods that rate below 50 are considered to have a low glycemic index, according to the University of Wisconsin. These foods raise blood sugar slowly over time, avoiding sharp increases or drops. The ADA reports that in general, foods with a high fiber and/or fat content tend to have lower GI values, as do foods that are closest to their raw forms. This includes raw low-sugar fruits and vegetables, beans and legumes.
Medium and High Glycemic Indexes
Medium GI foods rank between 50 and 70, and high GI foods are rated 70 and above, reports the University of Wisconsin. The medium group includes whole grain bread, brown rice, sweet potatoes, corn and honey. The high group contains such foods as cereal, candy, white bread and white rice. Eating higher ranking foods is not necessarily unhealthy. To avoid excessive blood sugar fluctuations, foods with high glycemic levels may be combined with those that are lower on the GI scale.
Can a Food's Glycemic Index Change?
Glycemic levels are not set in stone: It is possible for a food to rate higher or lower than usual based on its preparation or form. For example, similar baked goods can have different GI ratings depending on whether they use different types of flour. In addition, foods that are processed more or cooked longer may have a higher GI than those eaten in their raw form, or after minimal cooking. The ADA also warns diabetics to consider portion sizes: Eating twice the amount of pasta does not actually raise its glycemic level, but due to the amount of carbs consumed, it could potentially raise blood sugar even more.
