How is Glycemic
Index Measured
The glycemic
index (GI) is a measurement of the rate at which carbohydrate-containing
foods raise blood sugar (glucose) levels. See also Glycemic
Load
GI Food
Measurement Tests
The glycemic
index of a food is measured under strict test conditions. To measure glycemic
index, portions of a carbyhodrate food are fed to a panel of volunteers
who then give blood samples at regular intervals over 2 hours for determination
of glucose levels.
Measuring
Glycemic Index
- The GI
value of a food is assessed by giving 10 or more volunteer subjects
a serving of the food containing 50 grams of digestible (available)
carbohydrate.
- For example,
to test boiled spaghetti the subject is given 200g of spaghetti, which
supplies 50g of carbohydrate.
- To test
how the food raises blood sugar levels, a sample of blood is taken from
each subject every 15 minutes during the first hour and thereafter every
30 minutes. The blood sugar level of these blood samples is measured
and recorded.
- The blood
sugar level is plotted on a graph and the area under the curve is calculated
using a computer program. The subject's response to the food being tested
is compared with his/her blood sugar response to 50g of pure glucose.
(Glucose is the reference food and the testing of glucose on the subject's
blood sugar levels is done on a separate occasion.)
- The average
blood sugar response from 8-10 people will determine the glycemic index
(GI) value of that food.
High, Low
and Intermediate GI Foods
Glucose is
assigned an arbitary GI of 100. Foods with GIs below 55 are considered
to have a low glycemic index. Numbers above 70 indicate a high glycemic
index, and numbers between 55 and 70 are intermediate.
Effects
of High GI Foods
Foods with
a high GI score contain rapidly digested carbohydrate, which produces
a large rapid rise and fall in the level of blood glucose. In contrast,
foods with a low GI score contain slowly digested carbohydrate, which
produces a gradual, relatively low rise in the level of blood glucose.
Related Glycemic Index Links
Low
GI Diet
Low GI Diet Foods
Low-GI Diet Meals
Low GI Diet Snacks
How is Glycemic Index Measured
Glycemic Index Advice
Glycemic Index & Weight Loss
Glycemic Index Diets and Obesity
Low GI Diets: Weight Loss
Study
Glycemic Index: List of Foods
High GI Foods
Glycemic Index and Foods
What Determines Glycemic
Index Values of Carbs
Effects of Fiber on Glycemic Index
Value of Foods
Effect of Acid on
Glycemic Index Value of Foods
Effects of Fat on Glycemic Index Value
of Foods
Glycemic Index and Meals
Low GI Diet and Potatoes
GI Value of Rice, Potatoes,
Pasta and Bread
GI Value of Carrots
GI Value of Sugar
Glycemic Index and Fruit
Glycemic Index and Diabetes
Carbs and Glycemic Index
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