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.
Siobhan Gallagher | EurekAlert!
Europe’s Demographic Future. Where the Regions Are Heading after a Decade of Crises
10.08.2017 | Berlin-Institut für Bevölkerung und Entwicklung
Scientists reveal source of human heartbeat in 3-D
07.08.2017 | University of Manchester
Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.
As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
18.08.2017 | Life Sciences
18.08.2017 | Physics and Astronomy
18.08.2017 | Materials Sciences