The glycemic index,(GI) provides a measure of how quickly blood sugar levels rise after eating a particular type of food. The effects that different foods have on blood sugar levels vary considerably. The glycemic index estimates how much each gram of available carbohydrate in a food raises a person’s blood glucose level following consumption of the food, relative to consumption of pure glucose. The scale ranges from 0-100, with 100 being pure sugar. Foods with high GI tend to be simple, while foods with low GI seem to be complex. Foods with a score of 70 or higher are defined as having a high glycemic index; those with a score of 55 or below have a low glycemic index.
Many factors can affect a food’s glycemic index, including the following:
- Processing: Grains that have been milled and refined—removing the bran and the germ—have a higher glycemic index than whole grains.
- Type of starch. Starch comes in many different configurations. Some are easier to break into sugar molecules than others. The starch in potatoes, for example, is digested and absorbed into the bloodstream relatively quickly.
- Fiber content. The sugars in fiber are linked in ways that the body has trouble breaking. The more fiber a food has, the less digestible carbohydrate, and so the less sugar it can deliver.
- Ripeness. Ripe fruits and vegetables tend to have more sugar than unripe ones, and so tend to have a higher glycemic index.
- Fat content and acid content. The more fat or acid a food or meal contains, the slower its carbohydrates are converted to sugar and absorbed into the bloodstream.
- Physical form. Finely ground grain is more rapidly digested, and so has a higher glycemic index, than more coarsely ground grain.
Diets rich in high-glycemic-index foods, which cause quick and strong increases in blood sugar levels, have been linked to an increased risk for diabetes, heart disease, and overweight, and there is preliminary work linking high-glycemic diets to age-related macular degeneration, ovulatory infertility, and colorectal cancer. Foods with a low glycemic index have been shown to help control type 2 diabetes and improve weight loss. Other studies, though, have found that the glycemic index has little effect on weight or health. This sort of flip-flop is part of the normal process of science, and it means that the true value of the glycemic index remains to be determined. In the meantime, eating whole grains, beans, fruits, and vegetables—all foods with a low glycemic index—is indisputably good for many aspects of health.
To search some more of your favorite foods visit: www.glycemicindex.com, which has one of the most comprehensive and updated lists available.