However, the definitions, developed by a committee formed by the American Association of Cereal Chemists (AACC) International, remain a contentious matter, and continue to inspire heated debate even amongst the members of the committee themselves.
The AACC International's Glycemic (Net) Carbohydrate Definition Committee yesterday presented its definitions in an open forum at the ongoing World Grains Summit in San Francisco, where other industry members added their voices to the debate.
Led by Julie Jones of the College of St Catherine, St Paul, Minnesota, the committee has been embroiled in heated discussions surrounding the issue since October 2004. Its final definitions were decided upon as a form of compromise, to "provide a measurable definition that will enable manufacturers to communicate the glycemic response in grams per serving of food."
These were separated into four terms: 'available carbohydrate', 'glycemic response', glycemic carbohydrate', and 'glycemic impact'.
According to the definitions established, available carbohydrate is "carbohydrate that is released from a food in digestion and which is absorbed as monosaccharides and metabolized by the body".
Glycemic response is defined as "the change in blood glucose concentration induced by ingested food".
Glycemic carbohydrate is "carbohydrate in a food which elicits a measurable glycemic response after ingestion".
And glycemic impact is "the weight of glucose that would induce a glycemic response equivalent to that induced by a given amount of food".
"We started with one definition and ended up with four. That's an indication of how complicated the issue is," said Danisco's Stuart Craig, who is also AACC's international president.
"Like the work we've done with dietary fiber in the past, we recognize that this is not by any means the end point," he said at yesterday's forum.
Originally developed over 20 years ago to help diabetics manage their condition, the glycaemic index or GI ranks foods based on their effect on blood glucose levels.
Foods with a high GI (70 and above) are digested and metabolised rapidly, triggering large fluctuations of blood glucose levels and insulin demand, while low- or medium-GI foods (40-69) are digested and absorbed more slowly, giving a slower and sustained release of energy and contributing to longer-lasting feelings of satiety.
But as science emerges showing that low-GI foods can help control weight and more certainly, help reduce the risk of diabetes and related conditions, a wider cross-section of consumers is selecting foods based on the GI index.
However, a major obstacle when it comes to using GI as a measure of a product's health benefits is that this is not consistent. Scientific literature remains mixed and insufficient, and results in fuelling confusion rather than providing reliable guidance.
Indeed, the glycemic index equation is not quite as simple as "low GI= good and high GI= bad." For example, chocolate cake has what is considered a low GI, while some whole grain cereals can have a medium to high GI.
As a result, one concern expressed by some committee members was that people should not be given the green light to consume high quantities of certain products simply because these have a low GI.
Other industry members yesterday expressed fundamental concerns with using GI as a nutritional measurement. Consumers, they say, want simplicity, not a complicated, misleading measurement such as the glycemic index.
According to David Topping of Australia's CSIRO, GI is "excessively complicated" and is not useful for consumers. Other nutritional indications, such as whole grain content, would be more beneficial, he said.
However, consumers have nevertheless caught onto GI as a nutritional indicator, and this has started to affect purchasing decisions. According to Australian cereal firm Sanitarium, sales of its most popular cereal product, made with 97 percent whole grains, actually suffered because of its medium GI level.
"We haven't gone down the GI bandwagon by choice. But that's what consumers want," said the company at yesterday's forum.
The Glycemic (Net) Carbohydrate Definition Committee's definitions were an effort to address these concerns to an extent, by improving understanding and communication of GI. However, the committee said that more science is necessary to determine the health outcomes of the glycemic index, and until that is available it urges caution in the use of GI labels and claims.