The glycemic index (GI) of a food is a measure of how a specific food with carbohydrates causes blood sugar to rise. It is given as a number compared to the effect on your blood sugar of eating either glucose (a type of sugar) or white bread.
When you eat a food or beverage containing carbohydrates, your body breaks down the carbs into a type of sugar called glucose. The glucose goes into your bloodstream and causes your blood glucose (blood sugar) levels to rise.
Compare to low-glycemic foods, high-glycemic foods lead to a quicker and greater spike in blood sugar levels. These spikes are considered unhealthy for a few reasons.
They raise your average blood glucose levels.
They place a higher demand for insulin on your body.
They lead to more dramatic dips in blood glucose after the spike, potentially causing hunger, carbohydrate cravings, and weakness.
A low-GI diet can help you avoid the blood sugar roller coaster, but the GI is not on the nutrition label of most foods. Instead, you will probably to look at a list of the GI of foods. The following are several low-glycemic foods.
Glycemic Index and DiabetesCan a low-GI diet lower blood sugar if you have prediabetes or diabetes?
Probably, if you choose wisely. Low-GI foods are less likely to cause blood sugar spikes, and more likely to keep blood sugar stable in healthier ranges. You can help control prediabetes or diabetes with a diet based on nutritious, low-GI foods such as vegetables, beans, low-fat dairy, and whole grains, along with healthy proteins and fats. However, a diet high in unhealthy fats, fried foods, and processed meat may be low-GI, but is not likely to lower blood sugar.
Greens (spinach, kale, collards, beet)
Peppers (bell peppers, jalapenos, serrano, etc.)
Zucchini and crookneck squash
Glycemic Index, Weight Loss, and HealthCan a low-GI diet help you lose weight? Yes, but only if you are careful. Any diet can help you lose weight if you use it to limit calories.
To lose weight on a low-GI diet:
- Choose healthy, filling low-GI carbs, such as vegetables, beans, low-fat dairy, berries, and whole grains.
- Include lean proteins, such as tofu, chicken, fish, and eggs, and healthy fats, such as nuts, avocados, and olive oil.
- Include nutritious “no-GI” foods (lean proteins and healthy fats).
- Limit low-nutrition high-GI foods such as sweets, sugary beverages, and refined starches. Beware of low-GI foods that are high-calorie and low-nutrition, such as pizza and ice cream.
Whole wheat kernels
All-bran and Fiber One cereals
Oat bran and rice bran cereals
Whole grain pasta
Lasagna with meat and/or cheese, ravioli, tortellini, and other stuffed pasta
Whole-grain pumpernickel bread
Low-Glycemic Dairy and Dairy-Substitute Products
Skim, low-fat, and whole milk
Cheese (cheddar, swiss, mozzarella, brie, feta, blue, goat, etc.)
Soy milk and yogurt
Beans (chickpeas, kidney beans, pinto beans, black beans, navy beans, etc.)
Split peas, black-eyed peas
Edamame and roasted soybeans
Tofu and soy-based meat substitutes
Guessing the Glycemic IndexWhat if you do not know the glycemic index of a food? That could happen if food has not have been measured or if you do not have time to check its GI before you eat it.
You cannot know for sure, but the GI tends to be lower when:
- It is less processed. Whole grains are often lower-GI than refined, whole fruit is lower-GI than fruit juice, and raw carrots are lower-GI than cooked.
- It is higher in fiber, protein, and/or fat, and lower in sugar and refined starch.
- It is raw. For example, raw carrots are lower-GI than cooked, and al dente pasta is lower-GI than well-cooked.
- Ripeness. A soft, ripe banana has a higher-GI than a firmer, less ripe one.
Low-Glycemic Nuts and Seeds
Nuts (walnuts, macadamias, hazelnuts, almonds, cashews, etc.)
Seeds (pumpkin, sunflower, chia, flax, etc.)
Dark chocolate and 100% (unsweetened) chocolate
Chili with beans
Sandwich on whole-grain bread with meat/tuna/cheese and vegetables
Peanut butter sandwich on whole-grain bread
Burrito with beans, cheese, guacamole, salsa, and lettuce on whole-wheat tortilla
Soups with protein and vegetables
Salads with vegetables and beans, cheese, chicken, tuna, dressing, and/or nuts
Low-Glycemic, Less-Nutritious (Limit These)
Medium/High-Glycemic Nutritious Foods (Enjoy in Moderation)
Butternut, acorn, and other winter squash
Shredded wheat and many whole-grain cereals (choose unsweetened)
Carb-Free and Very Low-Carb Foods (Very Low GI)
Chicken, turkey, and other poultry
Eggs and egg whites
Fish and shellfish
Beef, pork, and other meat
Olive oil, canola oil, and other oils
Butter, shortening, and lard
Low-Glycemic May Not Mean Healthy (and Vice Versa)The GI is only one way to assess a food. Lower-GI often means healthier, but not always. For example:
- You can lower the GI of a slice of bread by spreading it with butter. That is not healthy!
- Boiled potatoes are high-GI and French fries are lower, but fries are not healthy!
- Oatmeal and pumpkin are high-GI, but they are rich in healthy antioxidants and fiber.
Atkinson FS, Foster-Powell K, Brand-Miller JC. International tables of glycemic index and glycemic load values: 2008. Diabetes Care. 2008;31(12):2281-2283.
Bove, A., Hebreo, J., Wylie-Rosett, J., & Isasi, C. R. (2006). Burger King and Subway. The Diabetes Educator, 32(5), 675–690. https://doi.org/10.1177/0145721706292737