Glycemic Index (GI)
What is GI?
Carbohydrate foods (i.e. breads, cereals, fruit, starchy vegetables, legumes, milk and yoghurt) are primarily broken down to glucose, which provides energy for our bodies. The Glycemic Index (GI) indicates how quickly different carbohydrate foods raise our blood glucose levels, ranking foods numerically, from 0 to 100.
Carbohydrate foods that are readily digested and cause blood glucose levels to rise quickly are called high GI foods (they have a value greater than or equal to 70). Foods that are broken down slowly and provide a more sustained supply of glucose for energy are called low GI foods (these have a value less than or equal to 55).
SOME EXAMPLES OF LOW GI FOODS*
|Food:||Low GI (GI<55)|
|Bread||Dense wholegrain and some high quality multigrain breads|
|Grains/Pasta||Rice noodles (fresh boiled), Barley (cracked or pearled)|
|Vegetables||Carrots, lentils, chick peas, kidney beans, baked beans, parsnip|
|Fruit||Apples, oranges, strawberries, pears|
|Dairy||Milk, low fat ice cream, low fat custard|
*The University of Sydney Glycemic Index foods search:
http://www.glycemicindex.com/foodSearch.php accessed 17 February 2014
THE RESEARCH ON GI AND HEALTH
Studies have shown that following a low GI diet may have benefits for improved management of blood glucose levels, weight control and in turn, may help reduce the risk of a number of health problems such as diabetes and cardiovascular disease.1-5
Research has also shown that consuming a low GI, low calorie diet may help in reducing metabolic disease risk factors associated with overweight and obesity6,7 and is an important dietary consideration in the management of diabetes, by helping to maintain small variations in blood glucose and insulin.8,9
Foods with a higher GI break down the fastest during digestion. High GI foods may be useful for some groups of people, such as athletes, who need a fast supply of glucose to fuel their muscles during competition.10
ARE LOW GI FOODS THE BEST CHOICE?
The inclusion of lower glycemic index (GI) carbohydrates, as well as reducing saturated fats and increasing fruit, vegetables and fibre can all form part of a healthy diet. Food choices should not be solely based on GI value alone. Eating a wide variety of foods from the core food groups11, and including some lower GI foods, is the key to a balanced and enjoyable way of eating.
HOW TO LOWER THE GI OF YOUR DIET
Getting the benefits from low GI eating doesn't need to be complicated. High GI foods do not need to be avoided, simply swap some carbohydrate foods to lower GI choices. Suggestions for lowering the GI of the diet include consuming one low GI food at each meal – for example, adding a low GI food like a tub of fruit yogurt to a higher GI food like watermelon may help to reduce the overall GI of the meal. Go to www.gisymbol.com to learn more about simple GI swaps.
SHOPPING – THE LOW GI WAY
Some food products have the GI value listed on the label. Those that have been tested at an Accredited Laboratory and meet stringent nutrition criteria so that they are all-round healthy choices carry the GI Symbol – go to www.gisymbol.com for further details and more information on following a low GI diet.
This fact sheet contains general information. Please consult your Accredited Practising Dietitian for specific advice for your personal situation.
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1. Livesey G, Taylor R, Livesey H and Liu S (2013). Is there a dose-response relation of dietary glycemic load to risk of type 2 diabetes? Meta-analysis of prospective cohort studies. American Journal of Clinical Nutrition 97(3):584-96.
2. Goff LM, Cowland DE, hooper L and Frost GS (2013). Low glycaemic index diets and blood lipids: a systematic review and meta-analysis of randomised controlled trials. Nutrition, Metabolism and Cardiovascular Diseases 23(1):1-10.
3. Pereira MA, Swain J, Goldfine AB, Rifai N and Ludwig DS (2004). Effects of a Low-Glycemic Load Diet on Resting Energy Expenditure and Heart Disease Risk Factors During Weight Loss. Journal of American Medical Association 292:2482-90.
4. Ebbeling CB, Leidig MM, Sinclair KB, Seger-Shippee LG, Feldman HA, and Ludwig DS (2005). Effects of an ad libitum low-glycemic load diet on cardiovascular disease risk factors in obese young adults. American Journal of Clinical Nutrition 81:976-82.
5. Larsen TM. Dalskov SM. van Baak M., et al., Diet, Obesity, and Genes (Diogenes) Project (2010) Diets with high or low protein content and glycemic index for weight-loss maintenance. New England Journal of Medicine. 363(22):2102-13.
6. Buscemi S, Cosentino L. Rosafio G., et al (2013) Effects of hypocaloric diets with different glycemic indexes on endothelial functiona dn glycemic variability in overweight and in obese adult patients at increased cardiovascular risk. Clinical Nutrition 32(3): 346-352.
7. Liu AG. Most MM, Brashear MM et al., (2012) Reducing the glycemic index or carbohydrate content of mixed meals reduces postprandial glycemia and insulinemia over the entire day but does not affect satiety. Diabetes Care 35(8): 1633-1637.
8. Louie JC, Markovic TP, Ross GP et al (2013) Timing of peak blood glucose after breakfast meals or different glycemic index in women with gestational diabetes. Nutrients 5(1): 1-9.
9. Marsh K, Barclay A, Colagiuri S, Brand-Miller J (2011) Glycemic index and glycemic load of carbohydrates in the diabetes diet. Current Diabetes Reports 11(2): 120-127.
10. Burke LM, Collier GR and Hargreaves M (1998), Glycemix index – a new tool in sport nutrition? International Journal of Sport Nutrition 8(4):401-15.
11. National Health and Medical Research Council (2013) Eat for Health. Australian Dietary Guidelines Summary (accessed 17 February 2014).