Ask The Expert
Eating Well

The Glycemic Index is a list of carbohydrate foods that ranks them according to how they affect blood glucose levels. It was developed over 20 years ago by researchers who helped to show that not all carbohydrates raise blood glucose levels the same amount. For example, the research showed that potatoes raised blood glucose more quickly than fruit, while legumes (lentils, beans, etc.) raised blood glucose more slowly.

You cannot obtain this information by reading a food label; rather, you have to have access to a glycemic index list, which is periodically printed in various diabetes magazines. I based this answer partly on the article "The Glycemic Index—What It Is and How to Use It" from the November/December 2000 issue of Diabetes Self-Management. Another resource was the ADA's Complete Guide to Carb Counting, by Hope Warshaw and Karmeen Kulkarni.

While the glycemic index was considered valuable research and it was put into practice in Australia, its use is not currently recommended by the American Diabetes Association (ADA). The ADA Nutrition Recommendations maintain that it is more important to focus on the total amount of carbohydrate in a meal rather than the source of the carbohydrate.

Partnership for Essential Nutrition Website Created to dispel myths:

Recently, several organizations (including the American Association of Diabetes Educators and the American Obesity Association) have formed a group to help educate the public on the important contribution that all food groups -- carbohydrates, protein and fat -- play in promoting good health and successful weight loss. The Partnership addresses the many misconceptions with various diets (such as low carb and glycemic index) so that you have complete, authoritative information upon which to make your food choices. You can read more about this in the related links.

There are many reasons why the glycemic index has not been considered practical for home use, mainly due to all the factors that can affect blood glucose:

• Eating only one food at a time is not how people really eat; usually, several foods are eaten in a meal, possibly containing high carbohydrate as well as high protein or fat.
• The fiber content of the food can slow the digestion process, which would lower the glycemic index of the food.
• Fat slows down the rate of stomach emptying, thus slowing digestion of carbohydrate. This is why a candy bar might have a lower glycemic index than a lower fat food item, such as a plain potato—but that doesn't mean the candy bar is nutritionally better than a potato!
• Types of starch: I don't want to confuse you with food chemistry, but suffice it to say that there are two types of starch in foods, which can affect their rate of digestion.
• Physical form of the food: an example would be the seed coating around legumes, which acts as a barrier to digestive enzymes, slowing the rate of digestion and lowering the glycemic index.
• The portion size of the food.
• The ripeness of the fruit or vegetable.
• Whether the food is cooked or raw.
• How quickly or slowly you eat.
• Your current glucose level: When blood glucose is high, stomach emptying is delayed; when the glucose level is low, stomach emptying is faster.
• How much diabetes medication you take.
• The time of your last medication, the time of day you ate, and the length of time since your last meal.
• Your level of physical activity.
• Your stress level and health status.

You can imagine that if you only ate foods with a low glycemic index, you would be limiting your food choices. An important guideline for healthy eating is to eat a variety of foods. Critics of the glycemic index are concerned with the food limitations, as well as the complexity of this concept—it would be too difficult to apply it to daily eating.

Putting this into practice:

Although experts do not recommend following the glycemic index principles exclusively, they do recommend that you learn as much as you can about how your body responds to various foods. The following are recommendations to help you apply these principles:

• Keep good records of the foods you eat, along with the dose of diabetes medication, amount of exercise, level of stress, and the times that all these things occur.
• Test your blood glucose before and after meals.
• You can eventually develop your own personal glycemic index—but be careful not to jump to conclusions too quickly since there are so many factors that can affect your blood glucose, as described above.