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.

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)

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