Rxtracts / Summary
This report gives the inter- and intra -individual variations of
glycemic index of white bread. Appears to clearly verify the
(modified)common claim that "Your Mileage May Vary --- A Whole Bunch".
"In our study the combined average was 71, virtually identical to the
published value. However, quite strikingly, individual values ranged
from 44 to 132. What is critical is to determine why there is such a
wide range of responses among individuals.
[ YMMV ]
....if a person eats a slice of turkey and cheese with that bread, the
effect of the multiple foods may result in a different glycemic index
than if that person had eaten the white bread alone. Since most food is
consumed as combinations during meals and snacks, there is a need to
assess the significance of using glycemic index values determined on
individual foods for food mixtures. Similarly, it is important to know
whether the food consumed prior to a meal or snack alters subsequent
glycemic response.
It is possible that we need to develop better research tools and more
stringent applications for glycemic index determinations," she says.
"Larger studies of diverse populations are needed to determine why
inter-individual, and particularly intra-individual, glycemic index
values are so variable....
Reference: Vega-Lopez S, Ausman LM, Griffith JL, Lichtenstein AH.
Diabetes Care. 2007 (June); 30 (6): 1412-1417. "Interindividual
Variability and Intra-Individual Reproducibility of Glycemic Index
Values for Commercial White Bread."
[ They got a 5 year grant study from the National Institute of Diabetes
and Digestive and Kidney Diseases to further their understanding of the
glycemic index and its utilities. The current study was supported by the
U.S. Department of Agriculture's Agricultural Research Service. ]
================= End Extract / Summary =============
Source: Tufts University, Health Sciences
Glycemic Index Values Are Surprisingly Variable, Researchers Report
Science Daily — In work investigating the reproducibility of glycemic
index values, researchers at the Jean Mayer USDA Human Nutrition
Research Center on Aging at Tufts University (USDA HNRCA) have reported
that multiple glycemic index value determinations (measure of the rate
of glucose absorption into the bloodstream) using a simple test food,
white bread, resulted in a relatively high level of inter-individual
(among different individuals), and intra-individual (within the same
individual) variability.
Further studies will focus on better defining the magnitude and the
sources of the variability. The intent is to better understand how
glycemic index relates to chronic disease risk in a wide range of
individuals.
Alice Lichtenstein, DSc, corresponding author and director of the
Cardiovascular Nutrition Laboratory at the USDA HNRCA and colleagues
assessed 14 study participants' glycemic response to 50 grams of
carbohydrate in the form of white bread (test food) and glucose
dissolved in water (control food) on different days. This experiment was
repeated three times with each individual.
"Using glucose as the control food, previous studies indicate that white
bread has a glycemic index of about 70," says Lichtenstein, who is also
the Gershoff professor of nutrition science and policy at the Friedman
School of Nutrition Science and Policy at Tufts. "In our study the
combined average was 71, virtually identical to the published value.
However, quite strikingly, individual values ranged from 44 to 132. What
is critical is to determine why there is such a wide range of responses
among individuals.
In addition, within the same individual, test values varied by as much
as 42 percent. "These results show that perhaps using glycemic index for
groups is a reasonable indicator to predict chronic disease risk, but
there is still considerable uncertainty when applying glycemic index to
individuals," explains Lichtenstein.
Glycemic index is a scale applied to foods based on how quickly the
glucose in foods is absorbed into the blood stream, relative to pure
glucose. Some nutrition professionals use the glycemic index as a tool
for people trying to control blood sugar, such as those with diabetes.
Others use the mean glycemic index of diets to predict chronic disease
risk in large groups of people. Potential confounding factors, such as
the fiber or fat content of the food, are not directly factored into the
calculations.
"There are many factors that can influence the glycemic index of a
food," says Lichtenstein. "For example, a piece of white bread may have
a high glycemic index but, if a person eats a slice of turkey and cheese
with that bread, the effect of the multiple foods may result in a
different glycemic index than if that person had eaten the white bread
alone. Since most food is consumed as combinations during meals and
snacks, there is a need to assess the significance of using glycemic
index values determined on individual foods for food mixtures.
Similarly, it is important to know whether the food consumed prior to a
meal or snack alters subsequent glycemic response.
It is possible that we need to develop better research tools and more
stringent applications for glycemic index determinations," she says.
"Larger studies of diverse populations are needed to determine why
inter-individual, and particularly intra-individual, glycemic index
values are so variable. If we can identify the source of the
variability, it will allow for more insight into the applications of the
glycemic index as a tool for both researchers and in public health
messages."
Lichtenstein and colleagues have received a five-year grant from the
National Institute of Diabetes and Digestive and Kidney Diseases to
further their understanding of the glycemic index and its utilities. The
current study was supported by the U.S. Department of Agriculture's
Agricultural Research Service.
Reference: Vega-Lopez S, Ausman LM, Griffith JL, Lichtenstein AH.
Diabetes Care. 2007 (June); 30 (6): 1412-1417. "Interindividual
Variability and Intra-Individual Reproducibility of Glycemic Index
Values for Commercial White Bread."
Note: This story has been adapted from a news release issued by Tufts
University, Health Sciences.