Glycemic Index: Does it have a role in diabetes management?

You have likely seen the words, “Low Glycemic Index!” on a variety of food products from cereal to snacks to ice cream to diet programs. What does it mean and what do you need to know?

What is the Glycemic Index?

The glycemic index (GI) measures how one’s blood sugar responds after eating a certain food. The rise in blood sugar is compared to the rise in blood sugar for eating the same amount of a reference food, typically either glucose or white bread. Glucose and white bread are generally reported as having GIs of 100. GI is reported as a percentage. Thus, a food with a GI of 45 could be deemed “low glycemic index,” whereas a food with a GI of 120 may be considered “high glycemic index.”

Applying Glycemic Index to diabetes management

While the concept of GI seems very legitimate and helpful in managing rises in blood sugars, there are some major flaws to be considered.

1. Unlike standard carbohydrate exchanges, GIs often vary significantly between different brands of the same food item, or even the exact same food. Using the International Table of Glycemic Index and Glycemic Load, a fairly comprehensive list of foods first published in 2008, foods like white bread have GIs that range from 63 to 101, depending on the brand. White bread that has been toasted has a lower GI between 50 and 72. There are three different entries for ‘banana’ with GIs ranging from 47 to 100.

2. Just as GI varies between brands of the same food, GI also changes depending of the reference food—glucose or white bread. Which is the better reference? Or which reference is used when a food is touted as “low glycemic index?” This information is generally not reported.

3. GI is not a reflection on a food’s overall “healthfulness” or nutritional value. Low GI foods may be low in nutrients and high in calories or saturated fat. For example, according to the International Table of Glycemic Index and Glycemic Load, Coca-Cola, a donut, and chocolate ice cream all have lower GIs than multigrain bread. Most dietitians would likely agree that multigrain bread is the preferred choice over cola, donuts, and ice cream.

What do the experts say?

The American Diabetes Association discusses GI as more of a way to fine-tune blood glucose management, rather than as the primary strategy:

“Combined with carbohydrate counting, it [GI] may provide an additional benefit for achieving blood glucose goals for individuals who can and want to put extra effort into monitoring their food choices. … For most people with diabetes, the first tool for managing blood glucose is some type of carbohydrate counting.”

The bottom line

When it comes to diabetes management, continue to use carbohydrate counting as the first step in blood glucose management. Remember the big picture—consider foods and meals for all of the nutrients they contain. And beware of food marketing tricks; the FDA does not regulate the use of claims related to GI.

If you have more questions about glycemic index or diabetes management, it’s always a great idea to speak with a registered dietitian. Registered dietitians are the only credentialed experts qualified to address your unique health questions.

References:

Atkinson FS, Foster-Powell K, Brand-Miller JC. International Tables of Glycemic Index and Glycemic Load Values: 2008. Diab Care. 2008; 31(12).

Glycemic index and diabetes. American Diabetes Association website http://www.diabetes.org/food-and-fitness/food/what-can-i-eat/understanding-carbohydrates/glycemic-index-and-diabetes.html. Updated May 14, 2014. Accessed January 28, 2018.

Wolever, TMS. Is glycaemic index (GI) a valid measure of carbohydrate quality? European Journal of Clinical Nutrition. 2013;67:522-531.