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Blood Glucose Levels

Limitations to the Glycemic Index

Home | Diabetes | Obesity | GI of foods | GI determination | Factors affecting GI's | Limitations | Wrap Up
Although the glycemic index does show some promise, there are several limitations to its success.

1. GI values are affected by eating a combination of foods: The glycemic index is based off of eating only one food at a particular time combined with nothing else except possibly water. Because of this, a major limitation to a diet based off of the glycemic index is the fact that foods are generally not eaten alone. It is difficult to estimate the effect a meal will have on blood sugar levels based off of the glycemic index. Some nutritionists suggest averaging the glycemic indexes of the particular foods eaten, but this can be highly inaccurate.

2. Foods containing fiber, protein, and fat: Foods that contain fiber, protein, and fat also affect the index because they usually decrease the rate of absorption of sugars.

3. Variations in the GI: There are wide variations in glycemic index measurements for the same food. An example from nutritiondata.com stated that one test gave a baked Russet potato a value of 56, while another one was given 111. This shows that the tests are not flawless and have a lot of variation.

4. Credible data: Another major limitation is the fact that there is a limited amount of information about the Glycemic Index that is credible. While scientific tests are continually being conducted, scientists are nowhere near knowing the glycemic indexes of every food product. Since the market is constantly changing, knowing all of them seems impossible.

5. Similar in composition? But different in value: Two foods that seem similar in composition to one another may have dramatically different indexes when tested. Sometimes the differences are due to processing, but everyday individuals would not notice a difference.

6. Causes overeating: Relying solely on the glycemic index values of foods is not a good choice because it may cause overeating. People may tend to choose items like meat or eggs over an apple because they have lower values. But, by not eating a balanced diet, many choose high fat and high protein foods thinking it will provide the most satiety, even though it is just providing a lot of extra calories.

Leslie Selcke
University of Illinois
FSHN 120 Honors Project
Fall 2005