Glycaemic Index 'unrealistic'
useful in understanding how diet impacts health," says the author
of a new study.
The use of glycaemic index (GI) to rank carbohydrates to their ability to affect blood glucose has become more and more mainstream, despite being complicated for the consumer to understand.
The general 'take-home' message for consumers has been "low GI good, high GI bad."
But a study published in the February issue of the British Journal of Nutrition reported: "The present results [of the study] call into question the utility of GI to reflect glycaemic response to food adequately, when used in the context of usual diet."
The researchers from the University of South Carolina evaluated GI in relation to blood sugar levels for 813 volunteers using a food frequency questionnaire.
After five years of follow-up the results showed that the GI of the diet was not related to any of the measures of blood glucose.
"There are valid reasons to question the Glycemic Index scientifically," said lead-author Elizabeth Mayer-Davis.
"This is an area in the field of nutrition that is controversial. It turns out that despite all of the interest in the Glycemic Index, the scientific literature is very mixed," she said.
Mayer-Davis explained that in scientific literature, a food's GI is based on fasting.
"This is unrealistic because we eat throughout the day, and a certain food eaten at lunchtime can have a different impact on blood-glucose levels compared to eatingthat same food for breakfast after fasting overnight," said Mayer-Davis."In general, the GI does not seem to be useful in understanding how diet impacts health, and use of the GI may not be an effective way to identify foods for optimal health," she said.
At the start of 2006, David Jago, director of Mintel's Global New Products Database, told NutraIngredients.com that he did not see GI as a fad, saying that the slow growth in popularity was usually associated with staying power.
However, Dr Glenn Gaesser, co-chair of the US Grain Food Foundation's clinical advisory board suggested last summer that the growth in popularity was being pushed by the industry.
"With the GI craze we have a case of the tail wagging the dog- everyone is following along for fear of losing market share.
The utility of the glycaemic index and glycaemic load (GL) with regard to health and weight control is overstated and not backed by a fair amount of published research," said Gaesser, in agreement with the South Carolina study.
