Latest GI research from America is seriously flawed and misleading
Australian glycemic index (GI) researchers have refuted the findings
of a recent American study published in the British Journal of Nutrition
that claims the GI is not a good indication of how food impacts blood
glucose.
The conclusions are based on a study with significant shortcomings, and
should therefore be viewed with caution, said Professor Jennie Brand-Miller
of Sydney University's Human Nutrition Department, one of the world's
leaders in Glycemic Index. She is astounded that it's being taken so
seriously but is "secretly pleased" at the fuss it's causing. "Hopefully
it means that the next positive study gets even more publicity."
The study, conducted by University of South Carolina researcher Elizabeth
Mayer-Davis and colleagues, contests the validity of the GI scale as
a tool for measuring blood glucose levels after eating.
The study used a food frequency questionnaire returned by 813 people,
which asked them to remember what foods they had eaten over the past
year.
The glycemic index is a ranking of carbohydrates in foods according to
how they affect blood glucose levels.
Prof Brand-Miller said the questionnaire did not effectively assess an
individual’s carbohydrate intake, and was therefore highly unlikely
to accurately estimate GI.
“
Like most current food frequency questionnaires, the questionnaire used
by the American researchers was not originally constructed for the purpose
of measuring true carbohydrate intake. In validation studies, the correlation
with food records was only 0.37 (above 0.5 is considered reliable). If
they can't measure carbohydrate well, it's unlikely they can accurately
predict the GI." Prof Brand-Miller said. She pointed to the large
number of well-designed experiments, during which people were given either
low or high GI foods, that have proven conclusively that the GI of a
person’s daily diet has a major impact on their average and fasting
blood glucose levels.
For example, a recent meta-analysis (the highest level of scientific
evidence) of low GI diets in the management of diabetes carried out by,
Professor Brand-Miller, showed clearly that blood glucose levels improved
significantly when individuals consumed a low GI diet for up to a year.
The results were published in the prestigious international scientific
journal Diabetes Care.
Professor Brand-Miller is a world-recognised authority on GI and was
a leading pioneer of the GI program when it was launched in Australia
in July on 2002.
She has published 16 books and 150 journal articles on the subject.
