PDA

View Full Version : Glycemic index question



paisano
06-27-2003, 04:54 PM
I was wondering how combining foods changes the glycemic value of a meal. For example, suppose you combine equal quantities of 2 foods. One has a glycemic value of 25, and the other is 75. Would the glycemic value of this meal be 50? Does it average out like that or is one more dominant than the other?

bradley
06-27-2003, 05:07 PM
I am not sure but I would think that your reasoning would be correct. That is assuming that you ate the same amount of each food.

bradley
06-27-2003, 05:08 PM
This is an interesting thread that might be of interest since you asked about the GI:)

http://www.wannabebigforums.com/showthread.php?s=&threadid=7510&highlight=insulin+index

paisano
06-27-2003, 06:47 PM
Thanks Bradley, good info at that link. Maybe I'm just splitting hairs trying to pinpoint an exact number. Lots of variables involved with this.

aka23
06-28-2003, 07:26 AM
Originally posted by paisano
I was wondering how combining foods changes the glycemic value of a meal. For example, suppose you combine equal quantities of 2 foods. One has a glycemic value of 25, and the other is 75. Would the glycemic value of this meal be 50? Does it average out like that or is one more dominant than the other?

The glycemic index is a measure of blood sugar response 2-3 hours after consuming 50g (usually 50g, sometimes otrher values) of non-fibrous carbohydrate.

If you are eating 25g of available carbohydrate of food 1 and 25g of carbohydrate in food 2, then taking the average is a reliable way to estimate GI. Some authors estimate the glycemic index of mixed meals using this method. However, if when you combine the foods you do not decrease quantity, then the combined blood sugar response is usually higher than either food alone. The glycemic index is a measure of quality, not quantity. Glycemic load better estimates the blood sugar responcse to a typical serving. The gylcemic load suggests that the blood sugar response to increased portions is linear. However, after reaching about 60g of available carbohdrate, the blood sugar often levels off.

So answering your question. If the portion sizes were cut in half and the amount of available carbs in the two foods were equal, then taking the average is a reliable measure. If the portion sizes were not cut and the amount of available carbs were equal, then adding is a decent way to estimate. However, this method fails for larger quantities. If the amount of available carbs is not equal, then you would need to figure the percentage of available carbs in each food and multiply by the appropriate factors.

In addition blood sugar is influenced by many external factors such as genetics, natural variations in the food, how food is cooked, speed food is eaten, when food is eaten, other foods eaten at similar times (including foods with few/no available carbs, such as animal products), etc. This makes the GI an imprecise measure.