Glycemic Index

Use glycemic index to help control blood sugar

POSTED AUGUST 13, 2012, 2:36 PM

Patrick J. Skerrett, Executive Editor, Harvard Health

Picture an old-fashioned roller coaster with plenty of ups and downs. That’s what your blood sugar and insulin levels look like over the course of a day. The highs that follow meals and snacks drop to lows later on. Learning to eat in a way that makes your blood sugar levels look more like a kiddie coaster with gentle ups and downs than a strap-’em-in, hang-on-tight ride with steep climbs and breathtaking drops can make a difference to your health.

How can you do this? A tool called the glycemic index (GI) can help. It rates carbohydrate-containing foods by how much they boost blood sugar (blood glucose). As someone with diabetes, I use the glycemic index as one strategy to keep my blood sugar under control. And there may be other benefits—low glycemic index diets have been linked to reduced risks for cancer, heart disease, and other conditions.

Comparing carbs

Carbohydrates are the main nutrient in bread, pasta, cereals, beans, vegetables, and dairy foods. All carbs are made up of sugar molecules. Some carbs, like sucrose (table sugar), are just a pair of linked sugar molecules, glucose and fructose. Other carbs, like the starches in potatoes, corn, and wheat, are a tangle of glucose molecules strung together in long chains.

How a carbohydrate-containing food affects blood sugar depends on how quickly the digestive system can break apart the food into its component sugar molecules. It also depends on the sugar molecules present.

The glycemic index measures how much a food boosts blood sugar compared to pure glucose. A food with a glycemic index of 28 boosts blood sugar only 28% as much as pure glucose; one with a glycemic index of 100 acts just like pure glucose. Over the past three decades, researchers have measured the glycemic index of several thousand foods. Click here to see the glycemic index of 100 foods. You can also look up glycemic index values from the University of Sydney’sGI website.

Glycemic index and health

New studies on how the glycemic index of a diet affects health are published almost every week. Some of the latest include:

• A low glycemic index diet can help maintain weight loss
• A high glycemic index diet has been linked to increased risk of prostate, colorectal, and pancreatic cancers
• A high glycemic index diet was linked to an increased risk of breast cancer
• A high glycemic index diet appears to increase the risk of cardiovascular disease
• The lower the glycemic index of a meal, the lower the blood sugar and insulin levels after eating

Using the glycemic index

Using the glycemic index to choose a healthier diet is easier than you might think. “It’s actually quite simple,” says Dr. Jennie Brand-Miller, a professor of human nutrition at the University of Sydney and an advocate of the glycemic index. “Swap high glycemic index foods for low ones.” See the table below for examples of these swaps.

Brand-Miller and others suggest three categories of carbohydrate-containing foods:

Low glycemic index (GI of 55 or less): Most fruits and vegetables, beans (Brand-Miller calls beans “star performers”), minimally processed grains, pasta, low-fat dairy foods, and nuts.

Moderate glycemic index (GI 56 to 69): White and sweet potatoes, corn, white rice, couscous, breakfast cereals such as Cream of Wheat and Mini Wheats.

High glycemic index (GI of 70 or higher): White bread, rice cakes, most crackers, bagels, cakes, doughnuts, croissants, waffles, most packaged breakfast cereals.

Choosing healthy, low-GI foods is easier in Australia, where hundreds of foods carry the GI label.

A few caveats

You can’t rely on the glycemic index alone for choosing a healthy diet. Some foods, like carrot and watermelon, have a high glycemic index, but a serving contains so little carbohydrate that the effect on blood sugar is small. Others, like sugary soda, have a moderate glycemic index because they contain a fair amount of fructose, which has relatively little effect on blood sugar. But they also pack plenty of glucose, which does boost blood sugar, cautions Dr. Frank Hu, professor of nutrition and epidemiology at Harvard School of Public Health.

The glycemic index of a particular food can also be influenced by what it is eaten with. Olive oil or something acidic, like vinegar or lemon juice, can slow the conversion of starch to sugar, and so lower the glycemic index.

The glycemic index isn’t a perfect guide for choosing a healthy diet. But it offers useful information that can help you choose foods that have kinder, gentler effects on blood sugar.

 Swaps for lowering glycemic index

Instead of this high glycemic index food	Eat this lower glycemic index food
White rice	Brown rice or converted rice
Instant oatmeal	Steel-cut oats
Cornflakes	Bran flakes
Baked potato	Pasta
White bread	Whole-grain bread
Corn	Peas or leafy greens
Fruit roll-up	Whole fruit Glycemic index and glycemic load for 100+ foods Glycemic index and glycemic load offer information about how foods affect blood sugar and insulin. The lower a food’s glycemic index or glycemic load, the less it affects blood sugar and insulin levels. Here is a list of the glycemic index and glycemic load for more than 100 common foods. FOOD Glycemic index (glucose = 100) Serving size (grams) Glycemic load per serving BAKERY PRODUCTS AND BREADS Banana cake, made with sugar 47 60 14 Banana cake, made without sugar 55 60 12 Sponge cake, plain 46 63 17 Vanilla cake made from packet mix with vanilla frosting (Betty Crocker) 42 111 24 Apple, made with sugar 44 60 13 Apple, made without sugar 48 60 9 Waffles, Aunt Jemima (Quaker Oats) 76 35 10 Bagel, white, frozen 72 70 25 Baguette, white, plain 95 30 15 Coarse barley bread, 75-80% kernels, average 34 30 7 Hamburger bun 61 30 9 Kaiser roll 73 30 12 Pumpernickel bread 56 30 7 50% cracked wheat kernel bread 58 30 12 White wheat flour bread 71 30 10 Wonderâ„¢ bread, average 73 30 10 Whole wheat bread, average 71 30 9 100% Whole Grainâ„¢ bread (Natural Ovens) 51 30 7 Pita bread, white 68 30 10 Corn tortilla 52 50 12 Wheat tortilla 30 50 8 BEVERAGES Coca Cola®, average 63 250 mL 16 Fanta®, orange soft drink 68 250 mL 23 Lucozade®, original (sparkling glucose drink) 95±10 250 mL 40 Apple juice, unsweetened, average 44 250 mL 30 Cranberry juice cocktail (Ocean Spray®) 68 250 mL 24 Gatorade 78 250 mL 12 Orange juice, unsweetened 50 250 mL 12 Tomato juice, canned 38 250 mL 4 BREAKFAST CEREALS AND RELATEDPRODUCTS All-Branâ„¢, average 55 30 12 Coco Popsâ„¢, average 77 30 20 Cornflakesâ„¢, average 93 30 23 Cream of Wheatâ„¢ (Nabisco) 66 250 17 Cream of Wheatâ„¢, Instant (Nabisco) 74 250 22 Grapenutsâ„¢, average 75 30 16 Muesli, average 66 30 16 Oatmeal, average 55 250 13 Instant oatmeal, average 83 250 30 Puffed wheat, average 80 30 17 Raisin Branâ„¢ (Kellogg’s) 61 30 12 Special Kâ„¢ (Kellogg’s) 69 30 14 GRAINS Pearled barley, average 28 150 12 Sweet corn on the cob, average 60 150 20 Couscous, average 65 150 9 Quinoa 53 150 13 White rice, average 89 150 43 Quick cooking white basmati 67 150 28 Brown rice, average 50 150 16 Converted, white rice (Uncle Ben’s®) 38 150 14 Whole wheat kernels, average 30 50 11 Bulgur, average 48 150 12 COOKIES AND CRACKERS Graham crackers 74 25 14 Vanilla wafers 77 25 14 Shortbread 64 25 10 Rice cakes, average 82 25 17 Rye crisps, average 64 25 11 Soda crackers 74 25 12 DAIRY PRODUCTS AND ALTERNATIVES Ice cream, regular 57 50 6 Ice cream, premium 38 50 3 Milk, full fat 41 250mL 5 Milk, skim 32 250 mL 4 Reduced-fat yogurt with fruit, average 33 200 11 FRUITS Apple, average 39 120 6 Banana, ripe 62 120 16 Dates, dried 42 60 18 Grapefruit 25 120 3 Grapes, average 59 120 11 Orange, average 40 120 4 Peach, average 42 120 5 Peach, canned in light syrup 40 120 5 Pear, average 38 120 4 Pear, canned in pear juice 43 120 5 Prunes, pitted 29 60 10 Raisins 64 60 28 Watermelon 72 120 4 BEANS AND NUTS Baked beans, average 40 150 6 Blackeye peas, average 33 150 10 Black beans 30 150 7 Chickpeas, average 10 150 3 Chickpeas, canned in brine 38 150 9 Navy beans, average 31 150 9 Kidney beans, average 29 150 7 Lentils, average 29 150 5 Soy beans, average 15 150 1 Cashews, salted 27 50 3 Peanuts, average 7 50 0 PASTA and NOODLES Fettucini, average 32 180 15 Macaroni, average 47 180 23 Macaroni and Cheese (Kraft) 64 180 32 Spaghetti, white, boiled, average 46 180 22 Spaghetti, white, boiled 20 min, average 58 180 26 Spaghetti, wholemeal, boiled, average 42 180 17 SNACK FOODS Corn chips, plain, salted, average 42 50 11 Fruit Roll-Ups® 99 30 24 M & M’s®, peanut 33 30 6 Microwave popcorn, plain, average 55 20 6 Potato chips, average 51 50 12 Pretzels, oven-baked 83 30 16 Snickers Bar® 51 60 18 VEGETABLES Green peas, average 51 80 4 Carrots, average 35 80 2 Parsnips 52 80 4 Baked russet potato, average 111 150 33 Boiled white potato, average 82 150 21 Instant mashed potato, average 87 150 17 Sweet potato, average 70 150 22 Yam, average 54 150 20 MISCELLANEOUS Hummus (chickpea salad dip) 6 30 0 Chicken nuggets, frozen, reheated in microwave oven 5 min 46 100 7 Pizza, plain baked dough, served with parmesan cheese and tomato sauce 80 100 22 Pizza, Super Supreme (Pizza Hut) 36 100 9 Honey, average 61 25 12 The complete list of the glycemic index and glycemic load for more than 1,000 foods can be found in the article “International tables of glycemic index and glycemic load values: 2008” by Fiona S. Atkinson, Kaye Foster-Powell, and Jennie C. Brand-Miller in the December 2008 issue ofDiabetes Care, Vol. 31, number 12, pages 2281-2283. February 3, 2015 Updated: February 5, 2015