Dana Whitham RD and Tasha Hamilton RD, CDE are dietitians at St. Michael's Hospital in Toronto.

Through research, we have learned more about how foods affect blood glucose levels.

When you eat a slice of bread, the flour from the bread breaks down into sugar (glucose) in your body to provide you with energy.

The same thing happens when you eat a piece of fruit, drink a glass of milk or eat a chocolate bar. Each of these foods contain a different kind of sugar. Fructose is a sugar in fruit, lactose is found in milk and sucrose is found in the chocolate bar. All of these sugars are broken down during digestion and provide you with energy.

The speed at which a food is able to increase a person's blood glucose levels is called the glycemic response. The glycemic response is influenced by many factors. Some factors may be the amount of food you eat, how the food is processed or the way the food is prepared. For example, pasta cooked 'al dente' (firm) is absorbed more slowly than pasta that is overcooked.

The glycemic index

The ranking of different foods based on their glycemic response was first studied by Dr. David Jenkins and colleagues at St. Michael's Hospital (Toronto).

The research team conducted several experiments looking at the speed at which different foods affect blood glucose levels and compared the numbers to a slice of white bread. White bread is given the glycemic index value of 100. Foods that have a value less than 100 are converted into sugar more slowly than white bread. Foods that have a glycemic index value greater than 100 turn into sugar more quickly than white bread.

Other researchers have used glucose as the reference food, so glucose would have a value of 100. Today either glucose or white bread may be used as the reference food (if white bread = 100, then glucose = 140). Current values listed in this article should be divided by 1.4 to obtain the Glycemic Index(GI) of a food for which glucose = 100.

What the researchers found surprised them. Foods such as milk and fruit tend to have a lower glycemic index value than common starchy foods such as bread, rice, potatoes and breakfast cereals. Even sugar (sucrose) had a glycemic index of 83, lower than some starchy foods.

The good news is foods that were previously avoided by people with diabetes can now be added to their diet in moderation.

Strategic eating

Selecting foods with a low glycemic index may help to manage your diabetes (see accompanying chart). Increasing the number of low glycemic index foods such as legumes, barley, pasta and whole grains (e.g., cracked wheat) in your meal plan may have real benefit in controlling blood glucose levels.

Most low glycemic index foods offer more fiber and are low in fat, both of which are recommended in Health Canada's Guidelines for Healthy Eating, as well as the Canadian Diabetes Association's nutrition guidelines .

High fiber foods also help lower your risk of heart disease. In fact, the Canadian Diabetes Association's Guidelines for the Nutritional Management of Diabetes in the New Millenium state that for every 10 gram increase in cereal fiber daily, the risk of heart disease decreases by 30 percent.

By simply including a high fiber cereal such as 1-1/2 cups of oatmeal in your meal plan, you will have added an extra 10 grams of fiber.

As well as incorporating oatmeal or other high fiber cereals into your meal plan more often, here are a few more low glycemia index tips for healthy eating: Prepare dishes with beans such as chili, soups, and salad.

Eat whole grain, pumpernickel and oat bran bread more often than white bread. Eat fresh fruit. Fruits have a low glycemic index, so they break down into sugar slowly in your body.

Canada's Food Guide recommends five to ten servings of fruits and vegetables every day. Enjoy a variety!

Eat parboiled, brown or white rice more often than instant rice.

Eat pasta, rice, yams, lima beans or baked potatoes more often than mashed, boiled or instant potatoes.

You should also remember that table sugar can produce a slower rise in blood glucose levels than potatoes, but it lacks the vitamins, minerals and fiber provided by the potato.

Decisions on foods must be made on the basis of overall nutrition, as well as the impact on blood sugar.

Also, don't forget about the roles that fat and protein will play. Protein and fat with our meals can also slow down the absorption of carbohydrates, which are converted into sugars during digestion.

Add fats in moderation to your foods and choose heart healthy fats such as non-hydrogenated margarine and vegetable oils.

The glycemic index is an average of the glycemic responses of many individuals. This index is fairly accurate and it is useful to determine your own blood glucose response to different foods and meal combinations.

Regular self monitoring of blood glucose and good note-taking can help you determine your individual glycemic response to food.

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