Glycemic Index and Smart Carb Choices

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Nutrition by the Numbers: Making Sense of the Glycemic Index

Can glycemic measures help you make smart carb choices?

By Elaine Magee, MPH, RD
WebMD Weight Loss Clinic - Expert Column

Reviewed By Kathleen Zelman, MPH, RD/LD

Low glycemic, high glycemic ... If you pay any attention to nutrition news, you've heard these terms more and more lately.

But what does it all mean? And is the glycemic index or GI -- essentially, a number that says how much your blood sugar rises after you eat a particular food that contains carbohydrates -- really the be-all, end-all to nutrition and health?

Well, not exactly.

High-GI foods (generally, things like white bread and white rice) give you a quick blood sugar boost that also fades quickly, leaving you hungry again. Lower-GI foods (think whole grains, produce, and beans) keep you feeling full longer as your blood-sugar levels rise more slowly.

But many researchers don't consider the glycemic index a valid tool. That's because it's based on how blood sugar rises in response to one particular food, such as carrots or rice. But we don't sit down to just a bowl of carrots or a plate of rice, do we? We eat foods together, as dishes and meals.

The presence of fat or fiber in a meal also influences how quickly our bodies metabolize the carbohydrates. So do some other factors, like how long noodles are cooked, or how finely grain is ground. (Slightly undercooked noodles are absorbed more slowly and have a lower GI; while the more finely a grain is ground, the more quickly its carbs are absorbed.)

What Exactly Is the Glycemic Index?

The glycemic index calculates how high your blood sugar rises in two hours after you eat a food containing roughly 50 grams of carbohydrates, compared to how much it rises after you eat a 50 gram serving of white bread or 50 grams of pure glucose (sugar).

The higher the GI for a certain food, the faster your body absorbs the carbs from that food. A lower GI means a food has a slower rate of carbohydrate absorption, and thus lower blood sugar and insulin peaks.

Here's where the controversy kicks in: whether low-GI foods lead to weight loss, lower blood sugar levels, and/or a reduced risk of heart disease and cancer compared with high-GI-foods.

After reviewing the existing research, the American Institute for Cancer Research (AICR) concluded that there was not enough evidence to recommend that people change their diets based on the glycemic index.

Enter a potentially more useful tool: the glycemic load, a more accurate measure of a food's effect on blood sugar levels.

A Better Measure

Think of the glycemic load as the glycemic index with attitude.

The GI tells you how quickly a particular carbohydrate in food makes your blood sugar rise, but it doesn't take into account how many carbohydrates are found in a serving. That means that some healthy, but relatively lower-carb, foods -- like carrots -- end up with a high GI number.

The glycemic load, meanwhile, takes the number of carbs per serving into consideration along with the food's glycemic index. To find a food's glycemic load, you basically multiply its GI value by number of carbohydrates per serving.

So the glycemic load allows us to compare the likely effect on blood sugar of realistic serving sizes of different foods.

What Influences the Glycemic Load/Index?

Many factors help determine your body's glycemic response to a particular food, including:

  • Physical form, such as a whole apple vs. applesauce. Mashing foods tends to give them a higher glycemic index/load.
  • Ripeness. The riper the fruit, the higher its glycemic index.
  • Fiber -- particularly viscous fiber, a type of soluble fiber found in oats, barley, and other foods. Generally, the higher the fiber, the lower the glycemic index/load.
  • Acidity. The higher a food's acidity, the lower its glycemic index/load.
  • Processing. The more processed or refined a food, generally, the higher its glycemic index/load will be. When a grain is in a more "whole" form, your body's digestive enzymes have a tougher time breaking it down, which lowers the glycemic response to it. (There are some notable exceptions: pasta, and parboiled and basmati rice tend to have lower glycemic indexes, especially if they're not overcooked.)
  • Whether protein and fat were eaten with the food. The presence of high amounts of protein and fat will decrease the glycemic index/load.

The following foods, even in large amounts, when eaten alone are not likely to cause a significant rise in blood sugar because they contain little carbohydrate: meat, poultry, fish, avocados, salad vegetables, eggs, fish, and cheese.

What's the Bottom Line?

I always look for the bottom line. And in the case of glycemic load, it tends to lead you to less-processed types of carbohydrate-rich foods, like vegetables, fruits, whole grains, and beans/legumes.

The truth is, there is plenty of evidence that a mostly plant-based diet can reduce your risk of diseases like cancer, heart disease, and diabetes. And these foods tend to have lower glycemic index numbers.

But we have yet to determine whether a low-glycemic-index diet is really what helps prevent disease, or whether this effect comes mostly from eating a healthful variety of foods.

Glycemic Load and Index Values for Common Foods

Here are glycemic index (GI) and glycemic load (GL) values for some common foods. I have included their fiber content as well. Keep in mind that GI/GL is just one tool. Other aspects of food, like vitamin, mineral, fiber, and phytochemical content, are also very important.

This table uses white bread as the reference for glycemic index. White bread has a glycemic index of 100 when used as the reference food.

Food GI GL *Fiber (g)
BEVERAGES
Milk, whole 38 4 0
Milk, skim 46 6 0
Chocolate milk (2%) 49 12 1.2
Coca-Cola 90 22 0
JUICES
Apple, unsweet 57 17 0.3
Carrot juice, fresh 61 14 1
Cranberry juice cocktail 97 33 0.3
Grapefruit, unsweet 69 12 0.3
Orange, unsweet 71 18 0.5
Pineapple, unsweet 66 22 0.5
Tomato, canned (no added sugar) 54 6 1.1
BREADS
Bagel, white (Lenders) 103 35 1.8
Baguette, plain 136 21 1.8
Oat-bran bread 63 11 1.4
Rye bread 71 8 1.8
White bread 100 14 0.7
100% whole-grain bread 73 10 4.5
BREAKFAST CEREALS
All-Bran (Kellogg's) 54 13 9.7
Bran Chex 83 15 4.9
Cheerios 106 21 2.6
Corn Chex 118 29 0.5
Cornflakes 130 33 0.8
Corn Pops 114 29 0.4
Cream of Wheat 105 30 3
Crispix 124 30 0.7
Froot Loops 99 25 0.6
Golden Grahams 102 25 0.9
Grape-Nuts 107 22 2.6
Oat bran, raw 78 4 1.5
Raisin Bran 87 17 4
Rice Chex 127 32 0.3
Rice Krispies 117 30 0.3
Shredded Wheat 107 21 3
Special K 98 19 0.9
Total 109 24 2.6
GRAINS
Barley, pearl 36 15 5.7
Buckwheat 78 22 6
Bulgur (cracked wheat), boiled 68 17 7
Corn, sweet, cooked 85 20 4
Couscous, boiled 5 min. 93 23 2.1
Oats, (as porridge) 83 18 4
RICE
Long grain, white unconverted, boiled 15 min. 71 29 0.6
Uncle Ben's parboiled, 20 minutes 107 39 0.6
Basmati, white 83 30 0.3
Brown rice, steamed 72 22 3
DAIRY PRODUCTS, ETC.
Vanilla ice cream, light (1/2% fat) 67 7 0
Chocolate ice cream, premium (15% fat) 53 6 0.5
Milk, whole 38 4 0
Milk, skim 46 6 0
Vanilla pudding (instant, made w/ whole milk) 57 8 0
Fruit yogurt (low-fat) w/ sugar 47 14 0
Fruit yogurt (nonfat) w/ acesulfame K and Splenda 33 6 1
Soy milk, reduced-fat 63 11 1
FRUIT
Apple 57 8 4
Banana 73 18 3
Cherries 32 4 2.8
Dates, dried 147 58 4.5
Grapefruit, raw 36 4 5
Grapes 66 11 1.2
Kiwifruit 68 7 4.1
Orange 69 7 3
Peach 40 62.4
Pear 54 6 3
Pineapple 84 10 1.5
Plum 34 41.8
Prunes, pitted 41 14 4.3
Raisins 91 28 3
Cantaloupe 93 6 1
Strawberries 57 1 2.8
Watermelon 103 6 0.6
LEGUMES/BEANS
Black-eyed peas 59 18 9.6
Garbanzo beans 39 11 6.6
Kidney beans (canned) 74 12 14
Black beans, soaked overnight, cooked 45 min. 28 7 13.1
Lentils, red 36 7 12
Pinto beans (dried), boiled 55 14 13
Soybeans, green, boiled 25 1 6.3
PREPARED/CONVENIENCE FOODS
Chicken nuggets 66 10 0.4
Fish sticks 54 10 0
French fries, from frozen 107 30 4.5
Pizza, cheese, from frozen 86 22 2
Pizza, vegetarian (thin crust) 70 17 3
PASTA/NOODLES
Fettuccine, egg noodles 57 25 2
Macaroni, boiled 5 min. 64 30 1
Spaghetti, boiled 5 min. 45 21 3.1
Spaghetti, boiled 11 min. (durum wheat semolina) 84 39 3.1
SNACK FOODS
Corn chips 60 15 1.8
Fruit bars, strawberry 129 32 0.5
Popcorn, plain, cooked in microwave 102 11 3
Pretzels, oven-baked 119 22 1
SWEETS
Chocolate (milk) 49 10 1.7
Chocolate (white) 63 18 0
Roll-Ups (fruit leather w/added vitamin C) 142 33 0
Jelly beans 112 30 0
M&M's, peanut 47 8 1
Snickers bar 97 32 1.5
Twix cookie bar 63 24 0.7
NUTS
Cashews 31 4 1.7
Peanuts 19 1 4
SUGARS
Honey 78 14 0
Sucrose (sugar) 97 10 0
VEGETABLES
Broccoli, steamed 0 0 2.5
Kale, cooked 0 0 2
Spinach, raw 0 0 2.2
Zucchini, steamed 0 0 1
Lettuce, Romaine 0 0 1
Green peas 68 4 4.4
Sweet corn, boiled 85 15 2
Carrots, boiled and peeled 70 3 3
Potato, baked (russet) 121 36 4
Sweet potato, baked with skin 69 22 6

Quick GuidePortion Control Tips: Lose Weight and Stick to Your Diet

Portion Control Tips: Lose Weight and Stick to Your Diet

*Fiber grams are based on the same serving size (generally, a typical serving for that particular food) from which glucose load was determined.

Originally published October 1, 2004.
Medically updated Oct. 7, 2005.

SOURCES: American Journal of Clinical Nutrition, July 2002. American Institute for Cancer Research. Livia Augustine, researcher in nutritional sciences, University of Toronto. WebMD Feature "Glycemic Index: New Way to Count Carbs?" by Sid Kirchheimer, published Aug. 20, 2003.

©2005 WebMD Inc. All rights reserved.

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Reviewed on 11/3/2005

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