What Is Glycemic Index? Examples of High GI and Low GI Foods

Nutritional sciences expert David Jenkins developed the glycemic index (GI) in the early 1980s to illustrate how certain foods containing carbohydrates, or carbs, affect blood sugar levels. The rankings of GI values are based on the speed with which the body breaks carbs down into glucose—a simple sugar—to be utilized for energy. For example, a high GI value of white bread indicates that your body can digest it quickly and break it down into glucose faster than a lower GI food, such as couscous.

The American Diabetes Association considers rankings at fifty-five or below to be “low”; rankings between fifty-six and sixty-nine to be “moderate” or “medium”; and rankings of seventy or above to be “high.”

In addition to GI figures, you can take into consideration glycemic load (GL) information, which will specify the quality, portion sizes, and the amount of carbohydrates found in common foods. Although certain foods may score medium GI to higher GI values, the glycemic load index can enable consumers to make more informed decisions. For people with certain health conditions, monitoring blood glucose levels and tracking the GI value and glycemic load values of their daily nutrition is a critical part of ongoing health care.

Learn a few examples of foods that are low and high on the GI (glycemic index) and how you can utilize glycemic load information (quality of ingredients, portion sizes, amount of carbohydrates) to get a clear picture of the nutritional value of foods. Here are some common food groups and how they typically rank on the GI:

• Bread: In general, breads score higher than most other foods on the GI; however, a bread’s processing method can impact exactly where it lands on the index. For instance, whole wheat bread made with mainly whole wheat flour is only slightly lower than white bread on the glycemic index, but it contains considerably more nutrients and minerals.
• Fruit: Most fruits receive low GI values, but there are some exceptions. Watermelon, for example, scores much higher on the GI than apples. However, once you consider the glycemic loads of both, it becomes clear that it would be difficult to consume enough watermelon to reach significant spikes in blood glucose.
• Starches: Although different cooking methods will change the GI value of starches, white potatoes typically score higher on the glycemic index than sweet potatoes. Regardless of the differing GI values, white potatoes are similar in nutritional value to sweet potatoes, with both containing many of the same vitamins and minerals.
• Legumes: Generally, legumes rank at the lowest end of the GI spectrum, although looking at the glycemic index alone might not be the best way to determine the overall nutritional value of a legume. For example, lentils contain twice the GI value of soybeans but contain more plant-based protein and fewer calories.
• Grains: Similar to starches, grains can have varying GI values depending on how you prepare the food. For instance, penne pasta has a similar GI value to porridge when boiled soft but a significantly lower GI value than porridge when prepared al dente.

Glucose is transported in the bloodstream throughout the entire body via the circulatory system. Therefore, blood sugar levels that consistently fall outside of a normal range can be one of many risk factors that contribute to overall health complications. Such complications can include high cholesterol, heart disease, obesity, or in some cases, type 2 diabetes. Learn more about blood sugar levels and the impacts of glucose levels on the body.

• Normal blood sugar levels: The American Diabetes Association defines normal blood sugar levels as less than one hundred milligrams per deciliter (mg/dl) during fasting (no meals for at least eight hours) and less than 140 mg/dl within a few hours after eating. Low GI foods, like chickpeas or kidney beans, may help maintain normal glucose levels through slower digestion.
  
• High blood sugar levels: Blood glucose will naturally spike after you eat, especially if the meal includes processed or other high GI foods, though chronic high blood sugar may be cause for concern. Consistently high blood sugar levels can damage the production of insulin in the pancreas and harden blood vessels, which could increase a person’s chances of future cardiovascular disease.
• Low blood sugar levels: Low blood sugar (also known as hypoglycemia) is commonly connected to diabetic medication, especially for patients with type 1 diabetes. Low blood sugar can usually be remedied with a snack consisting of high GI foods, such as breakfast cereals or apple juice, which can quickly raise blood glucose to normal levels.

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