Glycemic Index and Label Reading

By Melissa Majumdar, RD, LDN, CPT

A while back, I received this question from a blog follower:

"Is there a way to determine glycemic index by looking at the label?"

The answer is yes and no. The glycemic index (GI) of an item has been determined in a laboratory setting by comparing the rate of glucose, or in some cases white bread, entering the blood to sugar. Much of this research has been conducted and published through the University of Sydney in Australia. Their database is online and can be a good reference, although some of their foods will differ in ingredients and processing from American food. Assigned GIs are determined by feeding an amount of food equaling 50 grams of carbohydrates to fasting *healthy* participants and measuring the blood sugar changes over time. Unfortunately, not much research has been done showing the glycemic response within the diabetic clientel. In Australia, they even put the glycemic index rating right on the front of a product!

Many factors influence the glycemic index of a food including the fiber, protein, and fat content, manufacturing and processing practices, and other ingredients. For example, even though they are both oats, steel cut oats will have a much lower glycemic index than its highly processed cousin instant oats. Keep in mind that glycemic response differs from person to person due to genetics, hormones, activity, etc. Also, if the food is eaten in combination with other foods, the overall glycemic affect changes. Take a plain piece of bread which contains mostly carbohydrates and it will register high on the glycemic index scale (slightly lower if whole grain and less processed). Add some jelly to the toast and the glycemic affect increases; add peanut butter or turkey and the glycemic index is lower. Keep in mind that a low glycemic food does not necessarily translate to a healthy food. Despite its high sugar content, ice cream has an extremely low glycemic index because the high saturated fat content slows the absorption of sugar.

In short, the least amount of processing and more whole grains and fiber, the lower glycemic index. The more protein or fat contained within the food, the lower the glycemic index. Take home message: pay more attention to overall quality and quantity of the food than just the GI. Even a low GI food eaten in larger portions has a greater affect on blood sugars than a small portion of a high GI rated food. This principle is described as glycemic load and takes into account portion size (GL = GI x amount of carbohydrates)/100. Consider carrots - they have a relatively high glycemic index but the amount of carrots it takes to equal 50 grams of carbohydrates is about 87 baby carrots, not the traditional amount eaten!

Learn more about balancing your glycemic intake with your diet by getting a personalized Nutrition Plan from an EB Nutrition Registered Dietitian!