The Glycemic Index, or GI, is a ranking given to carbohydrates as a measure of their effect on blood sugar. A lower number on the scale means that a food is less likely to raise blood glucose. Consuming low glycemic carbohydrates can help reduce the risk of diabetes, heart disease and obesity.
What Is a Low GI?
The glycemic index scale ranges from 0 to 100, with 100 being a food that has the greatest effect on blood sugar. A carbohydrate food that scores 55 or lower is considered a low glycemic choice. These foods are typically lower in calories and higher in fiber.
Apples, especially those that are eaten fresh with the skin, are considered low glycemic carbohydrates and one of the lowest among all fruits. A raw apple has a GI ranking of 40, while sliced canned apples packed without juice has a GI of 42. Even 100% apple juice has a lower GI rating, as long as it is not sweetened with additional sugar. It is listed with a glycemic index of 44.
Many people believe that a banana should be avoided for those trying to control their blood sugar, but a standard serving of the fruit (1/2 a banana) is given a GI of 40-50. However, ripeness is a consideration. As a banana ripens, the starch is converted to sugar. An under-ripe banana has a GI of 30, while a ripe (all-yellow) banana is rated 51.
Carrots are another vegetable, along with potatoes, that tend to have a bad reputation among diabetics. Carrots, both cooked and raw, have a GI of under 35. Carrots are also an excellent source of carotenoids, which may be beneficial in blood sugar regulation. Some research has suggested that the beta-carotene in carrots is beneficial in preventing insulin resistance.
Many people are surprised to learn that pastas are generally low in their glycemic index. A serving of most types of noodles ranks around 50 on the glycemic scale. Pasta has a low GI because of the physical entrapment of the starch granule inside the gluten protein of the pasta dough. However, beware of overcooking pasta. This creates a change in the chemical structure, causing a more rapid digestion rate and a greater rise in blood sugar. Another consideration is portion size. Many people, when served a dish of spaghetti, eat more than one portion. This can significantly affect blood sugar by providing an excess carbohydrate load.
If you are looking for a breakfast food that is quick and easy and will not raise blood sugar too rapidly, look to those that contain oats or bran. All Bran with Fiber, for example, has a GI of 38. Other cereals with GI less than 55 include Muesli, Bran Buds and Oat Bran. Of course, you must consider the milk as well. All milk, whether whole or skim, has a GI of around 31 – so choose the skim to reduce the calories and fat in your breakfast meal.
A full list of food and their glycemic index can be found in the book "The New Glucose Revolution", by Jennie Brand-Miller PhD, Thomas Wolever MD PhD, Kaye Foster-Powell and Stephen Colagiuri MD.