The Glycaemic Index

The glycaemic index, or "G.I. Factor" as it is commonly known, is a way to compare the effect of different carbohydrate foods on the levels of sugar in our blood.

Carbohydrates are nutrients found in foods. They can be sweet, like those in sugar, or starchy like those in potato, bread or pasta. Like most foods, carbohydrate must be digested into its basic components before we can make use of it. Carbohydrates are digested to glucose that is absorbed into the blood stream to supply every cell in the body with the energy needed to function. Glucose is the body's preferred fuel and is used much like petrol for a car.

However, not all carbohydrates release glucose into the blood stream at the same speed. Some do it quickly, some more slowly. We used to think it was obvious - "simple" carbohydrates such as sugar, so named for their uncomplicated chemical make-up, were thought to be digested and absorbed more quickly than chemically "complex" carbohydrates like the starch in bread. But it is not that simple. The GI factor proves that the speed and extent of rises in blood glucose levels cannot be predicted by the "simple" versus "complex" definition of carbohydrates.

The GI factor measures what actually happens to blood glucose levels after eating different carbohydrate foods. The measurement for each food is compared to that of pure glucose to provide a ranking. Pure glucose is ranked at 100, and almost all other carbohydrate foods are ranked below this. The results have provided some surprises - some starchy foods such as potatoes have a greater effect on blood glucose that does sugar.

So, how does the GI measure help us?

Low GI

Foods with a low GI produce smaller rises in blood glucose levels which are sustained over longer periods of time than higher GI foods. Foods with lower GI are important for:

. maintaining the balance between protein and carbohydrate content - which leads to better hormonal balance;

. lower blood glucose levels for people with diabetes or insulin resistance;

. appetite and weight control - these foods "fill you up" more readily;

. lower insulin levels in the blood which are associated with lower risk of developing coronary heart disease

and NIDDM (non insulin-dependent diabetes mellitus).

Moderate GI

The table on the reverse side provides a guide to the GI of a variety of different foods. When choosing the foods that are best for you to eat, nutrient content (higher in whole, unprocessed, organic foods) is a separate, important requirement to the GI value. Try to balance protein and starchy or sugary carbohydrate foods in a ratio of 1:1 (by volume), choosing lower GI value carbohydrates where possible. You can then add as much non-GI vegetables (such as dark green leafy or other non-starchy vegetables) as you like.