There are no exact GI values available. In order to arrive at the average GI value of specific foods, various repetitive tests are done. Volunteers involved in the tests are exposed to six stages of testing. One might therefore find the values to differ somewhat from one reference source to another. I have used various sources, which makes the list below as representative of those averages as possible. But in general, the steps listed here are the most commonly used way in which the GI of food is determined.
During a test, a sample of blood is taken from a person who does not have diabetes and then he/she is asked to eat an amount of food containing 50 g of carbohydrate. (As a mailer of interest, that amount of carbohydrate is equivalent to 45 ml of pure glucose powder.) A 200 g portion of cooked spaghetti, for instance, will provide 50 g of carbohydrate, equal to 45 g of pure glucose.
During the first hour after the consumption of the carbohydrates, a sample of blood is taken every 15 minutes and for the following hour, every 30 minutes. The blood is analysed and blood sugar levels are measured and recorded in a laboratory. These levels are plotted on a graph, which will indicate the rate at which they rise.
The volunteer's blood sugar response to each particular kind of food is measured against the response to 50 g of pure glucose -the reference food.
The reference food is tested similarly on two or three separate occasions on the same person and from those readings an individual average value is calculated. This is done to minimise the effect of any daily variation in blood sugar responses.
The same tests are carried out on 8 to 10 different people, using the same kind of food as reference. Thereafter the overall average GI of that particular food is calculated.
Following is a list of the average GI values of our most popular and commonly eaten carbohydrates, to be used as a guide. Although all foods have GI values, those of carbohydrates are what affect us most; more so than protein, fat or dairy products and for that matter, most low-carbohydrate vegetables. Those foods in general have very low GI values and I see no point in including them on the list.
Experts advise that it is best to eat those carbohydrates with a GI below 55 at least 80% of the time. The list is therefore in ascending order to make your choices easier.
What is worth knowing at this point is that although a combination of certain foods can lower the overall GI of a meal or a snack, fat remains the danger zone for your weight and your health. Eating a croissant, for instance, will result in a slower rise of your blood sugar than any other kind of wheat-based bread, because the croissant contains loads of butter, which slows down the GI of the wheat flour, whereas ordinary bread does not contain much fat. Similarly, eating a fat-free baked potato will produce a faster rise in blood sugar levels than fat-rich potato crisps or chips would. But in these instances the harm done by the fat literally outweighs the lower GI and unfortunately the fat that goes with the croissant and the chips will soon attach itself to your hips, rendering your careful plans to eat low GI foods utterly fruitless.
The ideal way is to eat mostly low GI foods with a low fat content. That will slim you down faster than any diet you've ever been on Guaranteed.
Unlike the popular myth that fruit makes you fat because of its sweetness, fruit in general actually has a low GI value. It therefore combines well with high GI cereals. Although fruit is sweet, it contains fructose - pure fruit sugar. Compared to sucrose (refined sugar), it is the preferred sugar when you want to slim and be healthy. I urge you to use fructose in all your beverages and foods that need sweetening. It has a low GI value and is all round much better for your health than sucrose. You can buy it from most chemists, health stores and supermarkets (where you will find it on the sugar or health product shelves). If your local suppliers don't stock it, ask them to order it for you. Demerara (raw) sugar is your natural second choice. The latter resists heat better than fructose does, so its ideal for baking. However, demerara also has a GI of 100, so use it as the exception rather than the rule.
Dairy products in general have low GI values (artificially sweetened, low-fat yoghurt has a GI of 14) and so they combine well with high GI breads and cereals to slow down the overall rate of such a meal or snack. A good example of this kind of combination would be white bread with fat-free cottage cheese, tomato and herbs. The overall GI of that snack will be lower, and so -thank goodness -will be the fat content. If you added butter and/or cheddar cheese to the bread, you would also slow down the overall GI, but at the expense of your fat intake and your weight loss efforts,
Vegetables and protein foods such as meat, fish and chicken also have generally lower GI values. They therefore combine well with high GI carbohydrates in order to reduce the overall GI value of the meal in which they are combined.
But remember, foods that slow down the overall GI of a meal do not justify an overload of fat. Which means that fat, oil, fatty meat, buffer, cream cheese and solid cheeses such as cheddar remain firmly within the 'be cautious' zone!