The Glycemic Index

The glycemic index has become a buzz-word of sorts over the past few years. With more knowledge of macronutrient ratios and their effect on overall health and performance becoming common-place, more people are becoming aware of the quality, not just quantity of food that they consume. The glycemic index can be a very useful tool in deciding the carbohydrate composition of your diet, but it is not an end-all. If it is used correctly, in conjunction with some other basic information, it can become a useful part of a good overall approach to nutrition.

The glycemic index refers to a standard system of measuring the effect of a carbohydrate on a person’s blood-glucose level. In order to determine the index of a food, a cross-section of people each consumes a portion that contains 50g of carbohydrates, and then has the effect on their blood-glucose tested over the next two hours. The effect of this carbohydrate is compared to their reference reaction to 50g straight glucose (a 100 on the glycemic index). Once they compare the reactions of the entire group, they have an idea of the food’s Glycemic index. If a food has a high glycemic index, it is closer in blood-glucose reaction to actual glucose, which means it contains lots of quickly digestible carbohydrates that will cause rapid fluctuation of blood-sugar levels. If, on the other hand, it has a low glycemic index, this means that it is composed of more slowly digested carbohydrates that will help sustain level blood-sugar and energy levels.

So what does this mean to the normal athlete? The glycemic index can be used as a handy guide for making smart food choices. With a few exceptions, if a food has a low GI it will help stabilize energy levels throughout the day. It also has the potential for being less-refined and containing more essential nutrients. By attempting to compose your diet from low-GI carbs, healthy fats and lean proteins, you will be going a long way towards ensuring the healthiest diet possible.

The downside is that the glycemic index isn’t the end-all for nutritious food choices. At times, foods with a low-GI act very differently than we may think, causing a disproportionate blood-sugar and insulin response. The glycemic index also fails to take into account the relative sugar content for commonly-consumed portions of a food. A watermelon has a higher GI (80) than chocolate ice cream (57), but to consume the entire 50g of carbs would take 195g of watermelon instead of just 50g of the ice cream. Needless to say you’re much less likely to eat a detrimental amount of watermelon. The solution is to also make use of a scale called the glycemic load, which takes into account common portion sizes too. Though less-studied than the glycemic index, the glycemic load scale makes a useful addition to the entire equation.

In the end, any form of measurement is only as useful as you make it. I feel that a basic understanding of the principles behind the glycemic index and its derivatives is one great step towards gaining a deeper understanding of your diet. To me, this seems like the most important step towards healthier living. When you begin to enlighten yourself as to the processes you undertake on a daily basis, it becomes easier to make the healthy choices that make a big difference.

For more information about the glycemic index, check out the great food-database at:

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Written by Jesse Woody   
Friday, 17 March 2006 15:48
Last Updated on Wednesday, 22 March 2006 02:43