Bay Area Medical Information

Glycemic Index and Glycemic Load

The use of the terms Glycemic Index and Glycemic Load has become used more widely in an attempt to describe specific characteristics of carbohydrates.

Traditionally, food labels use a different system in that they will describe carbohydrates into 2 groups: sugars and fiber, with fiber broken down even further into 2 useful classes of soluble and insoluble fiber.

In other settings, carbohydrates are classified as either simple or complex. This categorization depends on the chemical structure of the food, and how quickly the sugar is digested and absorbed. Simple carbohydrates have one (single) or two (double) sugars. Complex carbohydrates have three or more sugars.

Examples of single sugars from foods include:

Fructose (found in fruits)
Galactose (found in milk products)
Double sugars include:

Lactose (found in dairy)
Maltose (found in certain vegetables and in beer)
Sucrose (table sugar)
Honey is also a double sugar. But unlike table sugar, it contains a small amount of vitamins and minerals. (NOTE: Honey should not be given to children younger than 1 year old.)

Complex carbohydrates, often referred to as "starchy" foods, include

Glycemic Index

Glycemic index (GI) is a number ranging from 0 to 100 that applies only to carbohydrate foods. It reflects how carbohydrate-containing foods affect blood glucose levels.

Foods with a score of 70 or higher are defined as having a high glycemic index and those with a score of 55 or below have a low glycemic index.

Carbohydrates with a higher glycemic index digest more quickly and tend to cause big spikes in blood sugar. These foods include highly processed foods made with white flour or white sugar. White potatoes also have a high glycemic index. A helpful way to remember some of the foods in this category is that many of them are "white", such as white bread, white sugar, white flour and white potatoes.

The lower the glycemic index, the slower the food is digested, allowing for glucose to be delivered more slowly to the bloodstream causing little effect on the blood sugar. Lower glycemic index foods include high fiber, whole grain foods and most nonstarchy fruits, vegetables and legumes.

There are limitations, however, in the accuracy of estimating a food's glycemic index. The mixture of foods eaten, the ripeness of foods, the degree to which the foods are cooked, and other factors can cause the glycemic index to vary.

Glycemic Load

Glycemic load is a more meaningful way to classify carbohydrates as it takes into account both the amount of carbohydrate in the food and the impact of that carbohydrate on blood sugar levels. The glycemic load is calculated by multiplying a food's glycemic index by the amount of carbohydrate it contains.

Several studies have shown that the chronic consumption of a diet with a high glycemic load is associated with an increased risk of developing type 2 diabetes, cardiovascular disease, and certain cancers.(2)

Glycemic Load of Certain Foods:(3) Carbohydrates with a low or medium glycemic load are the healthiest.

Low Glycemic Load (10 or under)

      • High-fiber fruits and vegetables (excluding potatoes)
      • Bran cereals (1 oz)
      • Many beans and legumes, including chick peas, kidney beans, black beans, lentils, pinto beans (5 oz cooked, approx. 3/4 cup)

 
Medium Glycemic Load (11-19)

      • Pearled barley: 1 cup cooked
      • Brown rice: 3/4 cup cooked
      • Oatmeal: 1 cup cooked
      • Bulgur: 3/4 cup cooked
      • Rice cakes: 3 cakes
      • Whole grain breads: 1 slice
      • Whole-grain pasta: 1 1/4 cup cooked
      • No-sugar added fruit juices: 8 oz

 
High Glycemic Load (20+)

      • Baked potato
      • French fries
      • Refined breakfast cereal: 1 oz
      • Sugar-sweetened beverages: 12 oz
      • Jelly beans: 10 large or 30 small
      • Candy bars: 1 2-oz bar or 3 mini bars
      • Couscous: 1 cup cooked
      • Cranberry juice cocktail: 8 oz
      • White basmati rice: 1 cup cooked
      • White-flour pasta: 1 1/4 cup cooked

References:

  1. "Carbohydrates and Sugars" from the USDA
  2. "International table of glycemic index and glycemic load values: 2002", American Journal of Clinical Nutrition, 2002 Jul;76(1):5-56.
  3. "Carbohydrates and the Glycemic Load", The Nutrition Source, Harvard School of Public Health

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