Carbs in Bananas - Glycemic Index and Load

Nutritional Information, Glycemic Index and Load, Carbohydrate Info

Bananas are a very good source of vitamin B6 and a good source of vitamin C, potassium and manganese. One medium banana has 17 percent of your daily value of vitamin C. You need vitamin C for the growth and repair of tissues in all parts of your body. It helps the body make collagen, an important protein used to make skin, cartilage, tendons, ligaments, and blood vessels. Vitamin C is needed for healing wounds, and for repairing and maintaining bones and teeth.

In addition, since resistant starch has been shown to contribute to healthy bacteria in our colons, green bananas could have health benefits along those lines.

Although a medium banana has approximately 1.3 grams of protein, bananas also have quite a bit of sugar, so low-carb dieters will probably not want to eat them very often, or at least in very measured amounts. And note that what is called a medium banana is not very big -- most bananas in the store are much larger.

Carbohydrate and Fiber Counts for Bananas

  • ½ cup sliced bananas: 15 grams effective (net) carbohydrate plus 2 grams fiber and 67 calories.
  • 1 medium banana (7 inches to 7¾ inches long): 24 grams effective (net) carbohydrate plus 3 grams fiber and 105 calories.
  • 1 large banana (8 inches to 8 and 7/8 inches long): 28 grams effective carbohydrate plus 3.5 grams fiber and 121 calories.
  • 1 extra-large banana (9 inches or longer): 31 grams effective carbohydrate, plus 4 grams fiber and 135 calories.

    Glycemic Index for Bananas

    The glycemic index (GI) of bananas varies depending on how ripe the bananas are. This is because a lot of the carbohydrate in green bananas is in the form of a kind of resistant starch which we lack the enzyme to digest. As the fruit ripens, the starch is converted into readily available sugars.

    One study of "under-ripe" bananas came up with a glycemic index of 30. One of "slightly under-ripe bananas" that were "yellow with green sections" produced a GI of 42, while another of "over-ripe" bananas was 52. However, most studies of bananas haven't specified the ripeness and have come up with GIs ranging from 46 to 70. An average of 52 is usually assigned to bananas.

    More Information about the Glycemic Index

    Glycemic Load of Bananas

    • ½ cup of sliced banana: 6
    • banana (7 inches to 7¾ inches long): 10

    More Information about the Glycemic Load

    Storing Bananas

    Did you know that it is a myth that bananas should always be kept at room temperature? The banana industry has been trying unsuccessfully to correct this misinformation for years. Although banana skins will turn black in the refrigerator, the fruit will spoil less quickly if it's refrigerated. 

    Low-Carb Banana Recipe

    More Carb Profiles:


      USDA National Nutrient Database for Standard Reference, Release 28.

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