By Julie Christensen
The glycemic index was originally developed by David Jenkins, a professor of nutrition at the University of Toronto, to help diabetics make smart food choices. The index ranks foods based on how quickly their carbohydrates are converted to sugar. Foods high in carbohydrates cause a spike in blood sugar, which stimulates the pancreas to produce insulin to regulate the sugars and convert them to energy.
Constantly high levels of insulin have several negative effects on your body. First, high levels of insulin slow your metabolism and make it difficult for you to burn fat and lose weight. When insulin levels are elevated, you’ll notice increased appetite and sugar cravings. High levels of insulin can put you at risk for hypertension, diabetes and heart disease.
The glycemic index uses a rating system of 1 to 100. Foods with an index between 70 and 100 are high in carbohydrates. Although most vegetables and fruits don’t fall in this category, the few that do should be eaten rarely. Those with a rating between 50 and 70 have moderate GI levels. They can be eaten in moderation. Fruits and vegetables with a glycemic index rating below 50 are considered low-GI foods. They can be eaten freely.
Fruits and Vegetables with a Low GI
As you can imagine, vegetables usually have a lower GI than fruits, simply because they have less sugar. Broccoli, cabbage, onions, peppers and mushrooms have a GI rating of 10, making them a good choice for every day.
While technically legumes, rather than vegetables, most beans, including dried beans have a low GI rating. Dried kidney beans and chickpeas are rated a 28, while lentils are rated a 29. Canned black-eyed peas have a rating of 42, while fresh green peas have a rating of 48.
Fruits on the low GI list include cherries, grapefruit, prunes and dried apricots, which all have a rating between 20 and 30. Apples, pears and canned peaches have a rating of 38; plums are 39 and strawberries are 40. Naval oranges and fresh peaches have a rating of 42, while grapes have a rating of 46.
Fruits and Vegetables with Moderate GI
Root vegetables often have higher GI ratings, because they’re high in starch. Beets, for example, are rated at 64. Corn is also high in sugar and starch, with a rating of 60.
Fruits in this category include cantaloupe (65), pineapple (66) and dried figs (61). Most tropical fruits fall into the moderate GI category. Mangoes have a GI rating of 51, while bananas are rated 52. Papayas have a rating of 57 and kiwis are rated a 58.
Fruits and Vegetables High in GIs
Most vegetables don’t fall into this category. The few that do include pumpkins, a type of winter squash that has a rating of 75, and potatoes, with a rating of 111. Watermelon is rated at 79, while dates have a rating of 103.
When it comes to choosing fruits and vegetables, consider more than just the glycemic index. Many fruits and vegetables, such as pumpkins, contain phytochemicals, powerful plant compounds that have been shown to reduce cell damage, improve immune function, and even prevent certain cancers. These foods are high in fiber and vitamins, while low in fat and calories.
If you rely solely on a GI rating, you could potentially consume many foods that aren’t that great nutritionally. Potato chips have a GI of 51; a slice of banana cake has a GI of 55. Although these two foods are considered moderate GI, they certainly aren’t as good for you as whole fruits and vegetables.
Make a habit of eating moderate portions and filling your plate mostly with fruits and vegetables, whole grains and lean proteins. Add desserts and processed foods sparingly for a simple, common sense approach to healthy eating.
For more information, visit the following links:
Gycemic Index and Glycemic load for 100 foods from Harvard Medical School
My Plate from the United States Department of Agriculture
Julie Christensen learned about gardening on her grandfather’s farm and mother’s vegetable garden in southern Idaho. Today, she lives and gardens on the high plains of Colorado. When she’s not digging in the dirt, Julie writes about food, education, parenting and gardening.