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As seen on BCTV November 26/02

THE GLYCEMIC INDEX

Carbohydrates in our diet, including starches and sugars, are digested and converted into glucose by the body. Glucose is then absorbed into the blood stream and circulates to all cells providing them with energy. Certain foods can become glucose and enter the blood stream faster than others and as a result increase a person’s blood glucose level or blood sugar faster. This is called the glycemic response. The Glycemic Index (GI) was developed to rank foods based on their glycemic response.

A major determinant of the GI of a food is the rate of carbohydrate digestion and metabolism. A food that is easily broken down during digestion and quickly absorbed has a high GI value. The blood glucose response is fast and high. A food that is digested and absorbed slowly has a low GI value. Foods can be classifies as having a low (<55), intermediate (55-70) or high GI (>70) with glucose as the reference standard. Some foods, such as legumes and milk products, tend to have low GI values while other foods vary from low to high within their food group.

A lower GI diet may be beneficial for people with diabetes and may help prevent certain diseases. The slow digestion and gradual rise and fall in blood glucose after a low GI meal helps control blood glucose. The use of low GI foods helps to prevent extreme blood glucose changes and the slow absorption of carbohydrates means the pancreas doesn’t have to work as hard to make insulin. The use of a low GI diet has been suggested for weight control and the use of a high GI diet may be helpful for athletes to improve performance, particularly during exercise.

Factors affecting the Glycemic Index

Cooking or processing starch: When a starchy food is cooked, the starch granules become swollen (gelatinized). Less gelatinized starch is digested slower resulting in a lower GI food. An example of this is pasta cooked to al dente is slower than overcooked pasta.

Sugar: Sugar helps prevent the gelatinization of starch granules. An example of this is Frosted flakes which is a slower carbohydrate than corn flakes.

Fibre: Soluble fibre slows down the interaction between the starch and our digestive enzymes and therefore foods with soluble fibre are slower carbohydrates. For example, rolled oats (not instant), beans, lentil and apples have low GIs.

Protein and fat: Both slow down the rate of gastric emptying and digestion of carbohydrates. Examples include yogurt, milk and legumes.

Acids in foods: Slow the rate of digestion and absorption. Adding vinegar, lemon juice and acidic fruits will lower the GI of a food.

High GI : more than 70
Glucose, Baguette, carrots, parsnips, Gatorade, instant potatoes, corn flakes, cream of wheat, pop, bagels, pretzels, frozen low fat yogurt with added sugar, mashed or baked potato, dried dates, instant rice, raisins

Moderate GI : 55-70
Rye bread, corn, pastry, bran muffin, whole wheat bread, basmati rice, white rice, cantaloupe, banana, honey, sucrose, bulgar, popcorn, yams

Low GI : less than 55
All Bran Buds with Psyllium, bran Flakes, barley, legumes, apple, cherries, grapes, milk, yogurt, ice cream, dried apricots, fructose, orange juice, chili, peanuts.

For more information visit www.glycemicindex.com

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Article written by Patricia Chuey and reprinted with permission