Dr Alan Barclay
The incredible GI journey
Research on the GI started a world-wide glucose revolution as it clearly showed that carbs didn’t affect our BGLs the way we thought they did at all. Initially freeing people with diabetes from overly restrictive diets, using the GI as a dietary tool has moved on to weight management and prevention of diabetes and heart disease. Today it's also being linked to inflammatory diseases, birth defects, memory, different types of cancer and healthy eyes. There’s even research that suggests that food ‘addiction’ is related to high blood glucose spikes. Prof Jennie Brand-Miller is currently involved in research applying low GI diets to pregnancy. Here are the some milestones in this new glucose revolution.
1977: Dr Phyllis Crapo and colleagues look at the effect of a range of different starchy foods on blood glucose and insulin levels in a group of 16 adults. When they compared the effect of a portion of food calculated to contain 50g available carbohydrate on the total area under the blood glucose and insulin curve for a period of 3 hours after eating, they found that corn and rice produced the lowest glucose and insulin response curves, and potato the highest, with bread in between.
1978: Using a similar methodology, Dr Mark Wahlqvist investigates the effect of 50g of glucose and a range of different starches on the total area under the blood glucose and insulin response curves in a group of 6 adults, for a period of 5 hours. Surprisingly to scientists and health professionals at that time, they found no differences in the glucose or insulin response between glucose and the different sized starches.
1981: Dr David Jenkins, Dr Tom Wolever and colleagues develop the concept of the glycemic index (GI). They fed groups of 5–10 healthy fasting adults, 62 commonly eaten foods each containing 50g available carbohydrate. BGLs were measured over 2 hours and expressed as a percentage of the area under the glucose response curve and compared with the same amount of carbohydrate consumed as pure glucose. Starchy vegetables like potatoes had the highest GI values (70%), followed by breakfast cereals (65%), cereal grains and biscuits (60%). Fruit (50%), dairy products (35%) and legumes (31%) had a relatively small affect on blood glucose in comparison. Despite controversial beginnings, the GI is now widely recognized as a reliable, physiologically based classification of foods according to their postprandial glycemic effect.
1994: American Diabetes Association guidelines drop specific recommendations for people with diabetes to limit the amount of ‘simple sugars’ – and most of the diabetes associations around the world quickly followed suit.
1995: Kaye Foster-Powell and Prof Jennie Brand-Miller publish the first International tables of glycemic index in the American Journal of Clinical Nutrition, bringing together all of the published data on the GIs of individual foods (almost 600). The tables show the GI according to the glucose and white bread standards, the type and number of subjects tested and the source of the data.
1997: WHO/FAO recommend that the terms ‘simple sugar’ and ‘complex carbohydrate’ no longer be used to describe carbohydrate foods. They recommend the use of the GI and total carbohydrate as the best guides to the effect of carbohydrate foods on blood glucose levels.
2002: Kaye Foster-Powell, Dr Susanna HA Holt and Professor Jennie Brand-Miller publish the revised International table of glycemic index and glycemic load values with almost 3 times the number of foods listed in the original table.
2007: The Cochrane Review of the evidence from randomised controlled trials on GI in the management of overweight and obesity finds that overweight or obese people on low GI diets lost more weight (measured in body mass, total fat mass and BMI) and improved their cholesterol profiles (total and LDL ‘bad’ cholesterol) more than those receiving conventional ‘healthy’ diets.
2008: The first systematic review and meta-analysis of all valid studies investigating the role of GI in the prevention of type 2 diabetes finds that high GI diets increase the risk of developing type 2 diabetes by 40%. This is comparable to the increase in the risk of developing heart disease when people consume a high saturated fat diet.
To improve the quality and quantity of GI data available for research and clinical practice, Fiona Atkinson, Kaye Foster-Powell and Prof Jennie Brand-Miller publish the International tables of glycemic index and glycemic load values: 2008 in Diabetes Care listing the GI of over 2480 individual food items.
2009: The Cochrane Review of all of the evidence from randomised controlled trials on the GI in the management of diabetes finds that the use of the GI by people with diabetes leads to a 0.5% point decrease in glycated haemoglobin, or HbA1c, above and beyond that achieved by regular healthy diets, plus it reduces the risk of hypoglycaemia. A 0.5% point decrease in HbA1c is equivalent to what many diabetic medications and insulin's can achieve, and will reduce the risk of common diabetic complications by 10%–20%.
2010: The International Standard designed to measure the glycemic index (GI) of foods (ISO 26642:2010) sets out the internationally recognised scientific method to determine the GI of foods to ensure nutrition and health claims made on food labels can be trusted and to assist food producers formulate healthier low GI products.
The DioGenes study determined that a healthy low GI diet, moderately high in protein, is the best eating plan for long-term weight management.
But while the science of GI is ongoing and can be complex, lowering the GI of your diet today isn’t. It’s really simple – you swap a high GI food for a low GI food from within food categories – a low GI bread instead of a high GI one, a low GI breakfast cereal for a high GI one. Here’s how:
The GI Symbol, making healthy low GI choices easy choices
For more information about the GI Symbol Program
Dr Alan W Barclay, PhD
Chief Scientific Officer
Glycemic Index Foundation (Ltd)
Phone: +61 (0)2 9785 1037
Mob: +61 (0)416 111 046
Fax: +61 (0)2 9785 1037