Glycaemic index, also known as GI, is used to rank carbohydrate foods on a scale from 0-100. Carbohydrate foods are foods containing sugars &/or starches eg bread, cereals, fruit, milk, yoghurt. During digestion carbohydrate foods are broken down into glucose. The GI gives an indication of the rate at which carbohydrate foods are digested and how they affect blood glucose levels.
How is GI ranked?
The GI of a carbohydrate food is classified as low, moderate or high.
GI Factor Low Less than 55 | Moderate 55-70 | High Greater than 70
A carbohydrate food that has a low GI is broken down and released into the blood slowly. However, carbohydrate foods that have a high GI are digested and released into the blood at a quicker rate.
How can someone with diabetes use the Glycaemic Index?
High GI foods result in more glucose being released into the blood at a faster rate and can make blood glucose levels more difficult to control. On the other hand, a low GI food can help control blood glucose levels as the break down of carbohydrate is slower and glucose is released at a slower rate. Studies have found improvements in blood glucose control in people following a low GI diet. To incorporate GI into your diabetes management, try including at least one food with a low GI at each meal. By combining a low GI food with a high GI food, the overall GI of the meal will be moderate. This will result in better blood glucose control.
What can affect Glycaemic Index?
There are many factors that can affect the GI of food. These include:
- Method of cooking and processing: the refining of products breaks up the food so it is digested more quickly. For example, white bread has a higher GI than whole grain bread.
- Type of sugar: the sugar found in food eg fructose, lactose is broken down more slowly than sucrose (white sugar).
- Fat and protein content: these delay absorption
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FOOD
White bread (1 slice, 30g)
Wholemeal bread (1 slice, 35g)
Multi-grain (1 slice, 30g)
Corn Flakes (1 cup, 30g)
Rice Bubbles (1 cup, 30g)
All Bran (1/2 cup, 40g)
White Rice (1 cup, 180g)
Basmati Rice (1 cup, 180g)
White spaghetti (1 cup, 180g)
Banana, raw (medium)
Orange (medium)
Apple (medium)
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GI
70
69
43
84
83
42
87
58
41
55
44
38
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For more information visit the Glycemic Index Web site (University of Sydney)