The concept of the glycemic index was first published in 1981 as, "Glycemic Index of Foods: a Physiological Basis for Carbohydrate Exchange," in the "American Journal of Clinical Nutrition." The groundbreaking idea was that different types of carbohydrates affect blood glucose levels differently; some cause the blood glucose level to jump rapidly, while others release sugars slowly and in even measures over time. This information was initially meant to be useful for diabetics, but has since become important to consumers interested in the health benefits of food.
Step 1
Gather a group of people to perform a formal experiment. Estimating glycemic index can only be done in a controlled environment with a control substance and the food that you are testing.
Step 2
Distribute a specified amount of sugar or white flour, usually 50 g, to the group. There are typically 10 people in the group, but you can have any number of test subjects.
Step 3
Chart the blood glucose levels of the test subjects over the next two hours. Measure the blood glucose level according to your equipment. It is typically a simple procedure that involves a finger prick and a blood sample that is read by a meter. Record the levels in 15 minute increments to produce a graph of glucose levels over time. The area under the resulting curve is what is measured, and it is called the incremental area under the blood glucose response curve, or IAUC.
Step 4
Administer the test food to the test subjects after they have been in fasting mode for at least 10 hours; the test is usually performed in the morning. A drink of water is often given with the test meal.
Step 5
Chart the blood glucose level for the next two hours the same way you charted the glucose levels for the control food. The IAUC is calculated the same way, as the area under the resulting curve.
Step 6
Divide the IAUC of the test food by the IAUC of the control food and multiply it by 100. This is the GI of the test food for each test subject.
Step 7
Add the results for each test subject together and divide the sum by 10 -- or whatever number of subjects you have -- to get the average GI.
Tips and Warnings
- You can perform this test as a series to test the GI of several foods.
- Since each person's body reacts differently, estimating GI is not an exact science.
Things You'll Need
- Test Subjects
- Control Food
- Test Food
- Blood sugar testing equipment
