The glycemic index is a system that ranks carbohydrate foods according to their immediate effect on blood sugar levels. Carbohydrates that break down quickly have a high glycemic rating; these foods can help replenish carbohydrate stores that have been depleted through vigorous exercise. Foods that break down slowly have a low glycemic rating, creating a smaller rise in blood sugar, and are therefore helpful for weight control. The index uses a scale that ranges from 0 to 100. Pure glucose is used as a reference, and is given a glycemic index of 100. The official Glycemic Index website, developed at the University of Sydney, considers foods with a glycemic index above 70 to be high. (Some sites give certain foods a glycemic index that is higher than 100; these sites are using an older version of the index, which uses white bread as the standard and ranks it at 100.)
Breads
High glycemic breads include white bread, with a glycemic index of 71; bagels, with a glycemic index of 72; kaiser rolls with a glycemic index of 67; and French baguettes, with a glycemic index of 95. The bread stuffing used on Thanksgiving has a glycemic index of 74.
Cereals
Most commercial cereals have a high glycemic index. For example, Crunchy Nut Cornflakes has a glycemic index of 72. Cheerios has a glycemic index of 74 and Kellog's Corn Flakes and Kraft Grape Nuts rank surprisingly high, with a rating of 71. Puffed Wheat has a glycemic index of 74. In general, processing cereal will increase its glycemic index.
Fruits
Watermelon, a favorite snack for kids, ranks high with a glycemic index of 72. In comparing various websites, you may find conflicting values for bananas. This is based on the ripeness of the fruit. For example, an under ripe banana may have a glycemic index of 30. In contrast, an over ripe banana may be as high as 70.
Snacks
Although donuts are often available at the starting point of a marathon, their glycemic index of 76 makes this high-sugar snack a poor choice for sustained energy. Additionally, think twice before you bring that bag of jelly beans. They have a glycemic index of 76. Rice cakes may be low-calorie, but they have a glycemic index of 72.
Potatoes
Although they are considered healthy, baked potatoes have a glycemic index of 85; mashed potatoes are even higher, with a glycemic index of 92. Although French fries have a glycemic index of 75, don't assume that they are healthier than baked potatoes.
Grains
Instant rice has a glycemic index of 87 and millet has a glycemic index of 71.
