THE GLYCEMIC INDEX HAS BEEN AROUND for some 25 years, though its appeal has only recently grown beyond those who use it for medical reasons. The system was originally developed to help diabetics and others with carb-sensitive conditions more accurately monitor and control their blood glucose levels.
More recently, low-carb dieters searching for a more sophisticated way to manage weight loss were attracted to the GI. Ditto the rise of long-distance athletics, where competitors were looking for foods that helped maintain a steady level of energy. Despite the new fans, however, overall acceptance of the GI has been tempered by a lack of endorsement from the U.S. government, and the fact that it can be difficult to compute.
"Many in the industry think that this will be the 'next big thing,"' said Allison Beadle, dietitian for H-E-B Central Market, San Antonio. "If this is the direction consumers are going, then it makes sense that retailers need to not only know about it, but understand its origins, the research behind it, and how manufacturers are applying it to their products."
There's more to computing the GI than reading labels or following diet books. For that reason, consumers who are familiar with the system are often extremely well-versed on diet and health, and respect retailers who stand ready to meet their needs.
At its simplest, the glycemic index ranks foods based on how they affect blood glucose levels. It applies almost exclusively to carbohydrates. Foods that take a longer time to digest, and therefore release their glucose more slowly, are assigned a low GI index, as opposed to foods that cause sudden spikes in blood sugar. These are assigned a high GI number.
In general terms, the lower the GI, the better. Sudden increases in blood glucose cause the pancreas to manufacture insulin to balance the abrupt flood of sugar in the blood, and this can damage the pancreas over time, possibly leading to diabetes.
Even short-term, high glucose levels can cause trouble, as the body takes the extra blood sugar and stores it as fat. Hence, the GI holds appeal for both those suffering from diabetes and dieters.
Experts point out that foods that have a lower GI are not always the healthiest options. Different types of sugars can have different effects on blood glucose levels because of the way they are digested, absorbed and metabolized. Factors affecting the glycemic response include the type of food, the amount and how it is processed or prepared. Personal factors include age, activity level and other foods that were eaten. This is where the glycemic load comes in.
The GL takes the glycemic index assigned to a food and multiplies it by the amount of total carbohydrates per serving. In using the glycemic load values, consumers can obtain a more accurate reading of the dietary benefits of the food. For example, carrots have a high GI but contain valuable nutrients as well. Carrots are also fairly low in carbohydrates so the GL value is low, telling the consumer that it's healthy to eat. Conversely, white potatoes have a high GI and are high in carbohydrates, making the GL high. This tells the consumer to use them sparingly.
The final version of the Dietary Guidelines for Americans published earlier this year did not incorporate any aspect of the glycemic index. That, coupled with the complex nature of the GI and GL system, has food associations expressing little interest at this point in including either on their product labels.
"I'd have to say that from the membership perspective, there's been little interest in use of the GI on food products," said Robert Earl, senior director of nutrition policy at the National Food Products Association. "I think [based on] the guidance from the government and what our organization supports, it's really quite clear that Americans should eat a variety of foods, get physically active and consume more fruits, vegetables, grains and low-fat dairy products."
A Grocery Manufacturers of America spokesman agreed, saying, "We're focused on the dietary guidelines. The dietary guidelines are the authoritative set of rules and authoritative guidelines on how to build a healthy diet."
Other countries are keener on the system. Australia has been including the GI on food and beverage labels since 2002. The licensed GI label appears on applicable products, and foods must meet certain criteria to be eligible for the GI symbol. Products in the United States that mention the glycemic index, or glycemic load, on their packaging include Solo GI Nutritional Bars, Kashi Cereal, Uncle Sam's Cereal and Snickers Long Lasting Energy Bar, among others.
"It's a platform that's great, not only for diabetics, but for everyone who wants to manage their weight and have sustained energy to get through the day in their hectic lifestyle," said Saul Katz, president and chief executive officer of Alberta, Canada-based Solo GI Nutrition. "Forty percent of the time, people are using a product on the go, and we need products that will support their health, give them energy, provide them with nutrients and focus on disease prevention."
The lack of political support hasn't stopped diabetes organizations around the world -- including Diabetes UK, Diabetes Australia, the Canadian Diabetes Association and the American Diabetes Association as of September 2004 -- from recommending that people use the GI as part of a complete approach to personal nutrition.
"Knowing only the amount of carbohydrates is not enough. Consumers expect more information about the quality of fats, such as trans, or saturated, as well as the quality of carbohydrates, both low GI and high GI," said Jennie Brand-Miller, a professor of human nutrition at the University of Sydney, Australia.