Just what is the Glycemic Index?
Magazines and the media seem to be full of buzz words for this trendy diet and that latest supplement â€“ leaving us wondering what the best approach for eating a healthy, balanced diet and maintaining an ideal body weight, without constantly yo-yo dieting, actually is. This month we will attempt to take the mystery out of The Glycemic index (GI).
The GI was derived by Dr. David Jenkins and his colleagues at the University of Toronto in 1981. It is basically a ranking of carbohydrates, according to the effect they have upon blood glucose levels two hours after eating.
Not all â€˜carbsâ€™ are equal â€“ some are bad for you and others are good. The speed with which a particular carbohydrate is absorbed by the body is dependent on a number of factors â€“ such as the type of starch it is made up of (amylose v. amylopectin), the fat content of the meal and its acidity. The way in which foods are prepared will also affect their GI value, as does the presence of dietary fibre.
The index scores carbohydrates up to a maximum of 100. Glucose itself is used as the reference in the index and is given a value of 100. High GI carbohydrates (i.e. those ranked at 70 or above) are digested quickly and lead to high levels of blood sugar soon after eating. They are ideal for rapid fuelling after exercise, when energy levels are depleted and need to be built up again, or for a person with diabetes experiencing hypoglycemia, but a diet consisting of predominantly high GI carbohydrate can lead to weight gain and poor health, since it leads to peaks and troughs of blood sugar levels and pushes our bodies to extremes. Moreover, we quickly become hungry again after rapidly digesting our food and want even more to keep hunger pangs at bay.
Low GI carbohydrates (i.e. those ranked at 55 or less) are digested and release glucose into the blood far more slowly, leading to smaller fluctuations in blood sugar levels. Eating predominantly low GI carbohydrate is the key to good health and sustainable weight loss. Other advantages of eating low GI â€˜carbsâ€™ include:
â€¢ Feeling fuller for longer after eating
â€¢ Reduce risk of heart disease
â€¢ Lower cholesterol levels
â€¢ Balanced energy levels
â€¢ Prolonged physical endurance
A quick and easy to use guide for calculating the GI value of the carbohydrate in your diet can be found online at www.glycemicindex.com. The following table will give you a general idea (from www.diabetesnet.com):
All Bran 51
Bran Flakes 74
Natural Muesli 54
Plain Yoghurt 14
Skimmed Milk 32
Soy Milk 31
Baked Beans 44
White Bread 70
Orange Juice 46