By now you've probably read or heard something about the glycemic index (GI). For example, how using the index to make food choices may help prevent and manage certain diseases, such as type 2 diabetes and heart disease. Many health organizations, including the Canadian Diabetes Association and the World Health Organization, support the use of the GI for individuals with diabetes.
But the GI is becoming an increasingly hot nutritional concept for people who don't already suffer from a chronic disease. Many prominent nutrition researchers and dietitians see it as a promising approach to healthy eating and the prevention and treatment of some chronic diseases.
The GI is a valid and potentially useful concept, but it is also complex and can be difficult to follow. Because the science around the GI is still quite young, there are some unanswered questions. As the science evolves, and researchers learn more about the GI and its role in the prevention and treatment of chronic diseases, these questions will be answered. Until then, here is a no-nonsense, nuts-and-bolts approach to incorporating GI principles into your family's diet.
What is the glycemic index?
Developed in the early 1980s by Dr. David Jenkins, a professor of nutritional sciences and medicine at the University of Toronto and a doctor at St. Michael's Hospital in Toronto, the glycemic index ranks carbohydrate-containing foods according to how they affect blood glucose, or sugar, levels.
The index measures how much your blood sugar rises after you eat a specific food; the higher the number, the greater the blood sugar response. Pure glucose is used as a reference food (it raises blood sugar the quickest) and is assigned the arbitrary value of 100. All other foods are then given a number relative to it.
How does the GI work?
The GI value of a food is determined by the speed at which your body breaks it down and converts it into glucose, or sugar, which is your body's main source of energy. High-GI foods are broken down quickly, causing a rapid rise in blood sugar, whereas low-GI foods take longer to break down, causing a slow, steady rise in blood sugar.
Page 1 of 7 -- Discover the health benefits of low-GI foods on page 2
Health benefits of eating low-GI foods
Research has shown that eating foods with a low GI may:
Prevent obesity: Low-GI foods may fill you up quickly and, because they're digested more slowly, stay in your stomach longer, making you feel full longer. As a result, you may end up eating less and consuming fewer calories. Because it is energy balance that keeps your weight in check (calories in equal calories out), consuming fewer calories may prevent you from putting on unwanted pounds.
Prevent type 2 diabetes: Type 2 diabetes is a condition in which blood sugar levels are higher than normal. It is caused by a lack of insulin, the hormone that helps your cells break down carbohydrates into sugar for energy.
If you have diabetes, either your pancreas doesn't make enough insulin and/or your cells don't respond to the insulin. As a result, sugar in the blood can't enter the cells, and they become starved for energy while your blood sugar remains high.
Because high-GI foods may increase insulin demand and raise the workload of the pancreas, some researchers think that many years of eating a diet rich in high-GI foods may cause the pancreas to wear out, resulting in type 2 diabetes. Eating low-GI foods can help reduce the demand on the pancreas so it doesn't have to work too hard.
Manage diabetes: Low-GI foods can help manage diabetes by controlling blood sugar and improving the body's sensitivity to insulin. These foods aren't converted to sugar as quickly as high-GI foods, so they may keep your blood sugar from spiking, which means your body can keep up with insulin demands. Keeping blood sugar levels under control is especially important for people with diabetes to avoid the serious complications of the disease.Prevent heart disease: Elevated insulin levels may be one of the promoting factors for heart disease. High-GI foods produce high spikes in blood sugar and insulin demand. This may raise your cholesterol and triglyceride levels, which can contribute to heart disease. On the other hand, consuming low-GI foods keeps blood sugar and insulin levels in check, thereby reducing your total blood cholesterol and LDL, or "bad," cholesterol, while increasing your heart-friendly HDL, or "good," cholesterol.
Page 2 of 7 -- Learn how to add both low- and high-GI foods to your meals on page 3
Do I have to give up high-GI foods completely?
Of course not! While many people may benefit from eating carbohydrates with a low GI value at each meal, this doesn't mean consuming them to the exclusion of all other carbohydrates.
All foods fit into a healthy diet, in moderation. And some high-GI foods make a valuable contribution to your diet. Mashed potatoes and white bread, for example, contribute energy and important nutrients, such as vitamin C, potassium, iron and a number of B vitamins.
Furthermore, when you eat a combination of low- and high-GI foods at a meal, such as peanut butter on whole wheat toast, or rice and lentils, the final GI value of the meal is medium. Base your food choices on the overall nutritional content in order to reap the nutritional benefits of many different foods, and try to eat a variety of foods from all four food groups in Canada's Food Guide to Healthy Eating every day.
Remember, the GI shouldn't be your only criterion for making healthy food choices. Healthy eating also means eating healthy portion sizes at regular times throughout the day, limiting sugars and sweets, eating foods that are high in fibre, and limiting salt, alcohol and caffeine. You also need to make sure you get enough healthy monounsaturated and polyunsaturated fats and reduce the amount of saturated and trans fats in your diet.
Does the GI increase with serving size?
No. The GI value of a carbohydrate-containing food remains the same even if you increase the amount you consume. On the other hand, if you eat more than one serving of the food, your blood sugar level will reach a higher peak and take longer to return to normal than it would if you ate a normal-size serving.
Page 3 of 7 -- Find out what influences the GI values of the foods you eat on page 4
What are some of the factors that influence GI values?
Type of starch. There are two types of starch in foods: amylose and amylopectin. Amylose has a lower GI rating because the molecules form tight clumps and are harder to digest. Amylopectin has a higher GI rating because the molecules are more open and are easier to digest. The more amylose starch a food contains, the lower the GI value of that food. For example, pasta, parboiled rice and many varieties of beans are higher in amylose starch and therefore have a low GI.
Cooking or processing starch: When a food is highly processed or cooked for a long time, the structure of the starch changes and the granules become swollen (gelatinized), softening the food and making it quicker to digest. The more quickly a food is digested, the higher the GI value. Less-gelatinized starch is digested more slowly, resulting in a lower GI. For example, al dente pasta has a lower GI than overcooked pasta.
Acids: Acids in foods slow down stomach emptying, thereby slowing the rate at which the food is broken down and lowering its GI value. Vinegar, lemon juice, lime juice, salad dressings, grapefruit, oranges, pickled vegetables and sourdough bread are good examples of acidic foods. Adding acidic foods to high-GI foods will result in an overall lower GI value.
Dietary fibre: Soluble fibre, such as that found in large-flake rolled oats, beans and apples, slows down digestion and lowers a food's GI.
Protein and fat: These slow down the rate of stomach emptying and carbohydrate digestion, which lowers the GI of the food. Some high-fat foods have a low GI and may seem like a good choice, but if the fat is saturated or trans fat, it may increase your risk of heart disease. The best advice is to look for foods that have a low GI and are low in saturated and trans fats. For example, chocolate cake with chocolate frosting has a lower GI than angel food cake, but is much higher in fat, thanks to the buttery frosting.Sugar: Sugar helps prevent the swelling (gelatinization) of starch granules. Less-gelatinized starch is digested more slowly, resulting in a lower GI. This helps explain why some cookies and frosted breakfast cereals have low GI values despite their high sugar content -- and not necessarily high nutritional values.
Page 4 of 7 -- Find out how you can add both high- and low-GI foods to your diet on page 5
Easy ways to add low-GI foods to your diet
• Choose breads that contain a high proportion of whole or cracked grains, stone-ground whole wheat flour, oats, bran and/or seeds.
• Choose unrefined cereals, such as large-flake rolled oats, oat bran, wheat bran, muesli and cereals made with psyllium.
• Choose brown, wild, basmati or converted (parboiled) rice.
• Try sweet potatoes for dinner instead of regular white potatoes.
• When baking, choose recipes that call for whole grain flours, oat bran, wheat bran, rolled oats or ground flaxseeds instead of, or in addition to, all-purpose flour.
• Snack on fruit, vegetables, yogurt or a handful of nuts (almonds, peanuts and walnuts are good choices because they also add healthy fats to your diet).
• Choose fruit- and dairy-based desserts, such as low-fat ice cream.
• Enjoy more pasta, legumes, vegetables and low-fat dairy products. (For scrumptious pasta recipes, log on to www.canadianliving.com to order your copy of Canadian Living Pasta by the Season.)
• Enjoy plenty of salad vegetables, such as lettuce, broccoli, cucumbers and tomatoes.
• Try tofu, barley, bulgur or lentils.
• Try to include at least one low-GI food at each meal.
Learn more about the GI
For more information on choosing low-GI foods, adapting recipes and incorporating low-GI foods into your meal plan, contact a registered dietitian. Check out www.dietitians.ca to find one in your area. The following books and websites also offer more information on the GI.
Books about the GI
• The New Glucose Revolution (Marlowe & Company, 2002) by Jennie Brand-Miller, Thomas M.S. Wolever, Kaye Foster-Powell and Stephen Colagiuri
• The G.I. Diet: The Easy, Healthy Way to Permanent Weight Loss (Random House Canada, 2002) by Rick Gallop
• Living the G.I. Diet: Delicious Recipes and Real-Life Strategies to Lose Weight and Keep It Off (Random House Canada, 2003) by Rick Gallop
Websites on the GI
Page 5 of 7 -- Thinking of what to have for lunch? Check out the low-GI lunch recipes on page 6
Low-GI breakfast and lunch recipes:
Whole Wheat Blueberry Apple Puff Pancake
There's no flipping required for this one-dish pancake. The blueberries are high in antioxidants and fibre, and the apples add even more fibre as well as a bit of sweetness. If your apples are on tart side, you can add a little more sugar substitute.
Crab Salad Melts
Whole grain pumpernickel bread has a lower GI than white bread and is a flavourful foil to the crab. Light-style Cheddar melts beautifully but isn't packed with fat.
Garden Egg Salad
Similar to salade Niçoise, this refreshing composed salad is chock-full of vegetables, chickpeas and hard-cooked eggs, and provides a good portion of your day's folate and vitamins A and C requirements.
More low-Gi inspiration:
Low-GI lunch meals
• Minestrone soup with yogurt and strawberries
• Whole wheat pita with hummus and a tossed salad
• Green salad with mixed beans and low-fat dressing and whole grain bread
• Grilled ham, cheese and tomato sandwich on sourdough bread with vegetable barley soup
• Leafy green salad with grilled chicken and a multigrain roll
• Salmon or tuna salad sandwich on stone-ground whole wheat bread with raw vegetables and dip
• Lentil soup with a pumpernickel roll and an orange
Low-GI breakfast meals
• Wheat or oat bran cereal with low-fat milk and berries
• Stone-ground whole wheat toast with low-fat cream cheese and sliced apple
• Yogurt and homemade granola made with large-flake rolled oats
• Whole grain pumpernickel bread with a slice of reduced-fat cheese and an orange
• Fruit smoothie made with low-fat milk, yogurt and berries
• Boiled egg with one slice multigrain toast and 1/2 cup (125 mL) cherries
• Homemade low-fat bran muffin and 1/2 cup (125 mL) strawberries
Page 6 of 7 -- Not sure what to make for dinner? Check out the delicious low-GI dinner recipes on page 7
Low-GI dinner recipes:
Roasted Vegetable Rotini and Cheese
This al dente pasta has a lower GI than pasta that is overcooked. Pasta is al dente when it is tender but firm when you bite into it. This child-pleasing dish is filling with or without the ham.
Roasted Red Pepper and Zucchini Soup
High-fibre, low-GI beans add body to this filling main-course soup, and whole wheat croutons have a little more fibre than store-bought white croutons.
Baked Tofu with Braised Baby Bok Choy
The low-GI combination of greens and tofu makes a terrific vegetarian meal, especially when served with basmati rice. The tofu can be a healthy portion of your day's protein, and if it's made with calcium sulphate, it can help you meet part of your daily calcium needs.
Chicken Burgers with Tomato Relish
You can grill these full-flavoured burgers on the barbecue or indoors in a grill pan, on an indoor grill, or in a nonstick skillet lightly brushed with oil.
Beef and Cabbage Borscht
Many traditional borschts contain beets, which are medium GI, so using beef instead lowers the GI and adds texture, some iron and protein, which may keep you feeling full longer.
Pork Cutlets with Mushrooms
Using whole wheat bread crumbs in these juicy pork cutlets is an easy way to incorporate more whole grains into your diet. Serve with steamed new potatoes.
Grilled Trattoria Chicken
Most of us need to eat more greens, and adding peppery arugula to salads or serving it with this grilled chicken is a good way to start. Try spinach, Swiss chard or blanched rapini instead of the arugula if you prefer.
The small amount of cheese on top of this nicely spiced turkey burrito adds a lot of flavour for not a lot of extra calories. An iron-rich spinach salad makes a particularly complementary side dish.
Chicken with Fennel Tomato Sauce
The tomatoes add a healthy dose of the antioxidant lycopene along with excellent flavour to this sauce. Bonus: the fennel-scented sauce only needs to simmer for 15 minutes.
Salmon with Lentil Pilaf
Lentils, like beans, add fibre to your diet and are the ultimate convenience legume since they don't require any soaking.
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