By its more common name, the glycemic index is a way of standardizing and measuring how quickly blood sugar (glucose) levels will increase after eating something. Different types of food will have different effects and these will vary from food to food. Examples of high GI foods include white bread, white rice, glucose, potatoes, and various maltodextrins. Low GI foods include beans, peanuts, walnuts, seeds, vegetables and certain fruits.

Glycemic Index Measurement

The glycemic index is a way of standardizing and measuring how quickly blood sugar (glucose) levels will increase after eating.The index measures carbohydrates on a scale of 0-100. Foods with high GI are rapidly digested and absorbed. These foods will have a quicker effect on glucose levels. Low GI foods by virtue are digested more slowly and cause a gradual rise in glucose levels. High GI foods can be used to cause a quick but short effect on glucose levels where low GI foods cause a slow and steady reaction. Low GI diets have been known to have a very positive effect on sufferers of Type 1 and Type 2 diabetes. The slower release of carbs means the glucose levels do not spike.

A common misconception about the GI index is that it measures the amount of carbohydrates in a food. While it does measure carbohydrates, it actually measures the ratio of them rather than the amounts. By eating twice as many carbohydrates, you are not doubling the GI of a particular food.

Calculating GI is done by using a sample of healthy adults and measuring the effects of the food consumed by them. Samples of blood are tested from the subjects in 15 minute intervals over a two hour period. The GI is then calculated by taking the average result of all the test subjects.

Glycemic Index and Disease Prevention

The Glycemic Index is a useful tool in disease prevention. Where high glucose levels persist over time, there is a significant risk of developing type 2 diabetes, coronary heart disease and some age-related degenerative disease. Studies have shown that people who follow a low GI diet are significantly less likely to be effected by these. Low GI diets effectively prevent hyperglycemia from occurring and studies from many universities and medical research organizations have shown this.

Insulin Response

The biggest criticism of the glycemic index is that it factors in only the glycemic response and not the insulin response. It is also applicable to carbohydrates and while a low GI diet may be a positive, it may not be ‘balanced’ in the way that a diet should be. The GI index is also criticized for portraying certain foods in a poor manner – notably white bread has a higher GI than cane sugar and no diet would profess more sugar than bread. Other tools such as the insulin index factor in a person’s response to glucose show the release of insulin. It has been argued that this is more accurate.


The glycemic index is incredibly useful as a standardized way of highlighting foods that can have negative long term effects on your health. Low GI diets have been proven to help sufferers of Type 2 diabetes by helping them manage glucose levels without having to over think what they are eating on a daily basis.