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!
Drone vs. truck deliveries: Which create less carbon pollution?
31.05.2017 | University of Washington
New study: How does Europe become a leading player for software and IT services?
03.04.2017 | Fraunhofer-Institut für System- und Innovationsforschung (ISI)
An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.
Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...
Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.
Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...
Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.
As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...
Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.
With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...
Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine
Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...
19.06.2017 | Event News
13.06.2017 | Event News
13.06.2017 | Event News
23.06.2017 | Physics and Astronomy
23.06.2017 | Physics and Astronomy
23.06.2017 | Information Technology