GI Science and Latest Emerging Research
A low GI diet could be beneficial for managing or preventing a number of health conditions.
New Report
This new report summarises 20 years of published scientific evidence on the glycemic index and its role in the prevention and management of lifestyle related chronic disease. This includes Type 2 diabetes and its complications, obesity and cardiovascular disease among others.
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The science of GI
The glycemic index, or GI, was discovered in Canada in 1981 by Professor David Jenkins. His research led to the first paper ever published on the glycemic index, which appeared in the American Journal of Clinical Nutrition that same year.
As well as providing an insight into the way carbohydrates in food affect blood glucose levels, GI has also challenged the myth that sugars and sugary foods are worse for blood glucose levels than starches and starchy foods.
The science of GI is constantly evolving. Scientists are now seeing that a low GI diet could be beneficial for managing or preventing other health conditions such as cognitive performance, skin health, reducing the risk of some cancers, improving eye health, as well as managing gestational diabetes and the symptoms of polycystic ovary syndrome.
First in low GI research
In 1995 The Sydney University Glycemic Index Research Service (SUGiRS) was established to provide a reliable commercial GI testing laboratory.
Food samples are tested in healthy volunteers according to standardised methods that have been validated against overseas laboratories. Testing of foods for their glycemic index, insulin index, satiety response, and other metabolic parameters can be assessed simultaneously. Other analyses such as in vitro starch digestion assays are available. SUGiRS has an established reputation for quality, speed and flexibility.
The Glycemic Index Foundation was established in 2001 in Australia, with the GI Symbol program launched in 2002 to help consumers identify the GI of foods. Foods that carry the Symbol are guaranteed to have been properly tested by an accredited laboratory using the international standard and meet nutritional criteria in line with International Dietary Guidelines – to prove it is a healthy choice.
There is convincing evidence from a large body of research that low glycemic index/glycemic load (GI/GL) diets reduce the risk of type 2 diabetes and coronary heart disease, help control blood glucose in people with diabetes, and may also help with weight management.
What is the food insulin index?
The glycemic index or GI, is a numerical ranking that provides a good indication of how fast the body is going to digest, absorb, and metabolise carb foods. However, this is not always proportional to the insulin response to a food.
When our blood glucose levels rise, our pancreas releases insulin (a hormone) that drives the glucose out of our bloodstream and into our body’s cells where our body can use it as an immediate source of energy or store it as glycogen. Some foods need more insulin to help utilise them, while other foods need much less.
Another measure that can be of use is the food insulin index (FII) which scientists at The University of Sydney have been researching for almost 20 years. The FII looks at how much insulin the body normally releases in response to a whole food or meal – not only in relation to the carbohydrate content, but also the quantity and quality of the protein and fat it contains.
In a recent study in the American Journal of Clinical Nutrition, University of Sydney researchers found that the FII may be an additional tool for people with type 2 diabetes to help them reduce postprandial hyperinsulinemia and improve insulin resistance and beta cell function.
Here are some tips to help people with diabetes achieve that:
- Balance meals with some carbs, lean protein and plenty of salad or vegetables as all foods stimulate some insulin response.
- Opt for lower FII carbohydrates such as pasta and noodles over higher FII ones such as most white rices and regular couscous when it comes to putting starchy carbohydrates on the dinner plate.
- Choose higher fibre, less processed breads and cereals, such as dense grainy bread and traditional porridge oats.
- Snack on fruit and non-starchy vegetables as they are low FII and packed with vitamins and minerals.
- Choose lean cuts of red meat, chicken or fish and team them with lots of non-starchy veg and/or salad. Processed meats like bacon and sausages may have a lower FII, but their high saturated fat content makes them a much less healthy choice.
Information courtesy of www.glycemicindex.com (September 2017)
Supported Research Activities
The Glycemic Index Foundation (GIF) is the world authority on the glycemic index (GI), its health benefits and how it can be used to guide your food choices. We do this by investing in research to better understand the Glycemic Index and associated health benefits of low GI eating and Low GL diets. The following are research projects supported by the Foundation:
Low GI diet more important than cutting sugar to reduce diabetes risk
There’s a common misconception, even among health professionals, that eating too much sugar can increase the risks of developing type 2 diabetes.
A new gold-standard global study has busted this myth.
The secondary analysis of PREVIEWfound that eating a low GI diet could be more important than cutting back on sugar, when it comes to reducing your risk of developing type 2 diabetes.
Dietary glycaemic index and glycaemic load among Australian children and adolescents: results from the 2011-2012 Australian Health Survey
This study aimed to examine the dietary glycaemic index (GI) and glycaemic load (GL) of Australian children and adolescents, as well as the major food groups contributing to GL, in the recent 2011-2012 Australian Health Survey. The paper concluded that, Australian children and adolescents appear to consume diets with a lower GI than European children. Exchanging high GI foods for low GI alternatives within core and non-core foods may improve diet quality of Australian children and adolescents.
Discovery of a lower glycemic index potato
Potatoes are a popular source of dietary carbohydrate worldwide and are generally considered to be a high glycemic index (GI) food. Potato starch characteristics play a key role in determining their rate of digestion and resulting glycemic response. The Glycaemic Index (GI) status of Carisma™ potatoes was established in a joint project between Sydney University and the Mitolo Group. The research was carried out by Kai Lin Ek, while working in the Faculty of Agriculture and Environment at the University of Sydney. The research showed that Carisma™ achieved the lowest GI compared to a number of potato varieties. Since the initial research, further testing and research has continued on Carisma™ and other potato varieties.
Macronutrient quality improves liver fat and Postprandial Glycemia in just two weeks
A 2019-2020 study at Maastricht University Medical Centre in the Netherlands investigated the effect on liver fat content and substrate metabolism of both reducing GI and saturated fat intake but in practical, realistic amounts under isocaloric conditions.
Thirteen overweight/obese individuals participated in a randomized crossover trial consisting of a two-week high-GI/SFA diet and a two-week low-GI/SFA diet separated by a washout period of at least 4 weeks with testing at the end of each period.
Changes in dietary glycemic index and glycemic load in Australian adults from 1995 to 2012
Australians have used the glycemic index (GI) since 1995; however, there are no data on changes in carbohydrate quality over time. The aim of the study was to compare average dietary GI and glycemic load (GL), and contributing carbohydrate foods, in the two most recent national dietary surveys. Although the average dietary GI and GL declined between 1995 and, trends in specific carbohydrate foods suggest that Australians are avoiding potatoes and sugary beverages in favour of a greater variety of carbohydrate foods, particularly cereal products.
Study: Low-GI diet lowers blood glucose in diabetes
People with type 1 or type 2 diabetes who followed a low-glycemic diet had a small yet clinically meaningful reduction in blood glucose levels, as well as reductions in fasting glucose, body weight, low-density lipoprotein cholesterol and C-reactive protein levels, compared with those who followed a high-glycemic diet. The findings published in The BMJ also showed that the positive effects of a low-GI diet among diabetes patients remained consistent over and above their existing drug or insulin treatments.
Dietary glycaemic index and glycaemic load among Australian adults – results from the 2011-2012 Australian Health Survey
This study aimed to determine the major food groups contributing to dietary glycaemic load (GL). Plausible food intake data collected using a multiple-pass 24 hour recall from a weighted sample of 6326 adult respondents (52% male) of the 2011-2012 Australian Health Survey dataset (AHS) were analysed. The mean (SD) dietary GI and GL was 54 (7) and 135 (59) respectively and the top three contributors to dietary GL were breads (14.4%), cereal-based dishes (10.3%) and breakfast cereals (ready to eat) (6.6%). There were small but significant differences in the GL contribution pattern between the sexes. The findings indicate that the average dietary GI of Australian adults is similar to that of other population groups, with a large proportion of starchy and energy-dense nutrient-poor foods that contribute to a high GL.
Prevention of Diabetes in Europe and Worldwide
The aim of the study is to determine the impact of a high protein, low glycemic index diet in combination with physical activity on the incidence of type two diabetes in overweight children and adults.
Professor Jennie Brand-Miller is leading the work program responsible for communicating and exploiting the findings of PREVIEW to convert new knowledge into strategies to reduce the risk of diabetes, including web-based lifestyle interventions for the public and collaborations between food industry and health professionals on development of innovative products and ingredients.
Dietary Glycaemic Index Labelling: A Global Perspective
At present, few countries regulate the inclusion of GI on food labels even though the information may assist consumers to manage blood glucose levels. Inconsistencies in food regulation around the world undermine consumer and health professional confidence and call for harmonisation. Global provisions for GI claims/endorsements in food standard codes would be in the best interests of people with diabetes and those at risk. This important paper was a global effort seeking input and direction from leading authorities in GI research, testing and labelling.
Research Activities
A low GI diet could be beneficial for managing or preventing a number of health conditions. This is evidenced by a wide body of existing and emerging research. See recent research supporting the growing scientific evidence in favour of a low GI lifestyle:
High glycemic index and glycemic load diets associated with increased risk of mortality
Study: Carbohydrate quality - not quantity - is more strongly associated with weight management
International Carbohydrate Quality Consortium
The International Carbohydrate Quality Consortium (ICQC) is a non-profit, worldwide organization whose mission is to support, summarize and disseminate the science around dietary carbohydrate and health with a focus on quality and to harmonize the work of scientists from academia, industry and government.
Further reading
- Glycaemic index, glycaemic load and cancer risk: results from the prospective NutriNet-Santé cohort
- Breakfast glycaemic index and exercise: combined effects on adolescents’ cognition
- Glycaemic index and glycaemic load of breakfast predict cognitive function and mood in school children: a randomised controlled trial
- A low glycaemic index breakfast cereal preferentially prevents children’s cognitive performance from declining throughout the morning
- The influence of the glycaemic load of breakfast on the behaviour of children in school
- Diet and acne: a review of the evidence
- Glycaemic index and glycaemic load in relation to risk of diabetes-related cancers: a meta-analysis
- Dietary glycemic index and glycemic load and risk of colorectal cancer: results from the EPIC-Italy study
- Dietary hyperglycemia, glycemic index and metabolic retinal diseases
- Does eating particular diets alter the risk of age-related macular degeneration in users of the age-related eye disease study supplements?
- Dietary glycemic index and the risk of age-related macular degeneration
- Randomized controlled trial investigating the effects of a low–glycemic index diet on pregnancy outcomes in women at high risk of gestational diabetes mellitus: the GI baby 3 study
- Carbohydrates, glycemic index, and pregnancy outcomes in gestational diabetes
- Can a low-glycemic index diet reduce the need for insulin in gestational diabetes mellitus? A randomized trial
- An isocaloric low glycemic index diet improves insulin sensitivity in women with polycystic ovary syndrome
- Dietary composition in the treatment of polycystic ovary syndrome: a systematic review to inform evidence-based guidelines
- Beneficial effects of a high-protein, low-glycemic-load hypocaloric diet in overweight and obese women with polycystic ovary syndrome: a randomized controlled intervention study
- Effect of a low glycemic index compared with a conventional healthy diet on polycystic ovary syndrome
For the latest GI related news from The University of Sydney
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