Carbohydrates and the glycemic index

A term that is used frequently is the glycemic index. The glycemic index serves as a relative indicator of the food's ability to raise the blood sugar level. The comparison is made by taking 50 grams of the carbohydrate containing food and comparing the blood sugar, over a two hour period to a standard, normally glucose which is given a value of 100.

A food with a glycemic index of 40 indicates that ingesting 50 grams of this food elevates the blood sugar to 40 % compared to 50 grams of glucose.

Not all carbohydrate containing foods are the same. We use the glycemic index to categorise foods. Frequent and excessive consumption of carbohydrates with a high glycemic index, such as sugar, may cause health problems ranging from obesity and type 2 diabetes to coronary heart diseases.



Carbohydrates such as sugar are quickly absorbed into the blood from the digestive tract. Eating highly processed foods rich in simple sugar, such as sweets and soft drinks, causes blood sugar levels to suddenly rise thus stimulating pancreatic cells to secrete an oversupply of insulin. Frequent overproduction of insulin may cause an insensitivity to insulin and a condition known as type 2 diabetes. Insensitivity to insulin requires progressively greater quantities of the hormone to control blood sugar levels. Type 1 diabetes occurs when the pancreas can not produce enough insulin to regulate blood sugar levels.


Rice, bread and pasta remain a favourite source of carbohydrate for athletes. The carbohydrate in these foods is in the form of starch. The unrefined forms of these foods, brown rice, multigrain bread and whole-grain pasta provide low glycemic sources of carbohydrates. The extra fiber found in these foods slows the rate of digestion. Absorption of sugar into the blood stream is slower and the blood sugar level does not spike. This eliminates the overproduction of insulin from the pancreas.
Define the glycemic index.
What can you say about a food that is labelled as having a high glycemic index?
What can you say about a food that is labelled as having a low glycemic index?
Explain why excessive consumption of foods with a high glycemic index are likely to cause type 2 diabetes.