The glycemic index (GI) measures how quickly a food will raise your glucose level. Avoiding fluctuations in your blood sugar can reduce your risk of developing insulin resistance, associated with type 2 diabetes and heart disease. Many popular diets, such as Atkins, the Zone and South Beach, are based on choosing carbohydrates that are low on the GI and have little effect on your blood sugar. Fiber slows the absorption of glucose into your bloodstream, so fruits high in fiber tend to be low on the GI.
Citrus Fruits
Of all the citrus fruits, grapefruit has the lowest GI score -- 25. Oranges are also a low-GI fruit, with a score of 44; any food with a score of less than 55 is considered a low-GI food. The sweeter the citrus, the higher it will be on the GI, although the high fiber content of clementines, tangerines and other citrus hybrids ensure they are all low-GI foods. There can be a great difference in the GI score of a fruit and its juice because of the lack of fiber in juice. A grapefruit has a GI of 25, but grapefruit juice scores are almost double at 48.
Cherries
Cherries, which score 22, have the lowest GI score of all fruits. All foods are scored in comparison to pure glucose, which scores a perfect 100 on the GI. Cherries are high in fiber and contain some protein, which slows the absorption of glucose and helps keep your blood sugar levels stable.
Apples, Pears, Peaches and Plums
Fruit with a high pectin content, a type of fiber, are low on the GI. Although the average apple scores 38, a green apple, which is higher in fiber and contains less natural sugar, will score slightly lower on the GI. Pears also score 38, plums score 39 and peaches score 42. Foods that concentrate the fruit, such as apple butter or peach preserves, will be higher on the GI. Jams, jellies and preserves, especially those with added sugar, are usually not low-GI foods. Beware of canned fruit in heavy syrup -- peaches in heavy syrup have a GI score of 64.
Tropical Fruits
Bananas score a 54 on the GI, the cut-off to be considered a low-GI food. Kiwi also just makes the cut, with a score of 53. If you are following a low-GI diet to lose weight, such as the Zone or South Beach, eat these fruits sparingly. Many tropical fruits such as mango and pineapple are medium-GI foods. Pineapple scores a 66, even higher than many fruit-based foods that have added sugar. The highest of all fruits is watermelon, with a score of 72. Any food with a score over 70 is considered to be a high-GI food and should be avoided on GI-based diet programs.
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