Someone posted this in the PEERtrainer community on a
thread debating how good bananas were for people looking to lose weight.
The glycemic index is a ranking of carbohydrates based on their
immediate effect on blood glucose (blood sugar) levels. It compares
foods gram for gram of carbohydrate. Carbohydrates that breakdown
quickly during digestion have the highest glycemic indexes. The blood
glucose response is fast and high. Carbohydrates that break down
slowly, releasing glucose gradually into the blood stream, have low
glycemic indexes.
What is the Significance of Glycemic Index?
• Low GI means a smaller rise in blood glucose levels after meals
• Low GI diets can help people lose weight
• Low GI diets can improve the body's sensitivity to insulin
• High GI foods help re-fuel carbohydrate stores after exercise
• Low GI can improve diabetes control
• Low GI foods keep you fuller for longer
• Low GI can prolong physical endurance
What is Glycemic Load?
• Glycemic load builds on the GI to provide a measure of total glycemic response to a food or meal
• Glycemic load = GI (%) x grams of carbohydrate per serving
• One unit of GL ~ glycemic effect of 1 gram glucose
• You can sum the GL of all the foods in a meal, for the whole day or even longer
• A typical diet has ~ 100 GL units per day (range 60 - 180)
• The GI database gives both GI & GL values
How to Switch to a Low GI Diet
• Use breakfast cereals based on oats, barley and bran
• Use "grainy" breads made with whole seeds
• Reduce the amount of potatoes you eat
• Enjoy all types of fruit and vegetables (except potatoes)
• Eat plenty of salad vegetables with vinaigrette dressing
Glycemic Index Range
• Low GI = 55 or less
• Medium GI = 56 - 69
• High GI = 70 or more
Measuring the GI
To determine a food's GI rating, measured portions of the food
containing 10 - 50 grams of carbohydrate are fed to 10 healthy people
after an overnight fast. Finger-*** blood samples are taken at 15-30
minute intervals over the next two hours. These blood samples are used
to construct a blood sugar response curve for the two hour period. The
area under the curve (AUC) is calculated to reflect the total rise in
blood glucose levels after eating the test food. The GI rating (%) is
calculated by dividing the AUC for the test food by the AUC for the
reference food (same amount of glucose) and multiplying by 100 (see
Figure 1). The use of a standard food is essential for reducing the
confounding influence of differences in the physical characteristics of
the subjects. The average of the GI ratings from all ten subjects is
published as the GI of that food.
The GI of foods has important implications for the food industry.
Some foods on the Australian market already show their GI rating on the
nutrition information panel.Terms such as complex carbohydrates and
sugars, which commonly appear on food labels, are now recognised as
having little nutritional or physiological significance. The WHO/FAO
recommend that these terms be removed and replaced with the total
carbohydrate content of the food and its GI value. However, the GI
rating of a food must be tested physiologically and only a few centres
around the world currently provide a legitimate testing service.
Glycemic Index Foods
Food category
Breads
White bread 70
Wholemeal bread 69
Pumpernickel 41
Dark rye 76
Sourdough 57
Heavy mixed grain 30-45
Legumes
Lentils 28
Soybeans 18
Baked beans (canned) 48
Breakfast cereals
Cornflakes 84
Rice Bubbles 82
Cheerios 83
Puffed Wheat 80
All Bran 42
Porridge 46
Snack foods
Mars Bar 65
Jelly beans 80
Chocolate bar 49
Fruits
Apple 38
Orange 44
Peach 42
Banana 55
Watermelon 72
Dairy foods
Milk, full fat 27
Milk, skim 32
Ice cream, full fat 61
Yogurt, low fat, fruit 33
Soft and sports drinks
Fanta 68
Gatorade 78