The Canadian Voice
From "Challenge",Newsletter of the IDAA/DESA, (14,3;winter 2000-2001)
Guide to the Glycemic Index
Sandra Turnbull, RDN, CDE - sturnbul@vanhosp.bc.ca

Although many people know about exchange lists (foods grouped by similar nutrients) and carbohydrate counting as useful ways to plan their meals and help control blood sugar, many more are asking questions about a relatively new (and still controversial) concept called the glycemic index.
The glycemic index , developed in 1981 by. Dr. David Jenkins, a nutrition professor at the University of Toronto , distinguishes between types of carbohydrates and measures how quickly they become glucose in the body. He looked at the speed at which different foods affect blood glucose levels and compared the numbers to a slice of white bread. White bread is given the glycemic index value of 100. Foods that have a value less the 100 are converted into sugar more slowly than white bread. Foods that have a glycemic value greater than 100 turn into sugar more quickly than white bread (1). Looking at the table below may surprise you.
Foods such as milk and fruit tend to have a lower glycemic index value than common starchy foods such as bread, rice, potatoes and some breakfast cereals. Even table sugar (sucrose) has a glycemic index of 83, slower than some starchy foods.
Selecting foods with a low glycemic index value may help you to manage your diabetes. Increasing the number of low glycemic foods such as legumes, barley, pasta and whole grains in your diet may have real benefit in controlling blood sugar levels (2). Most low glycemic index foods are higher in fibre and low in fat, something dietitians have been advocating for years. Il is important to remember that while table sugar may produce a slower rise in blood sugar than potatoes it also lacks the vitamins, minerals and fibre provided by the potato. Decisions on food choices must be made on overall nutrition as well as the impact on blood sugar.
Where I think using the index shows interesting promise is in helping to regulate blood sugars during exercise. Faster carbohydates (higher numbers) could be used for raising low blood sugars and for covering brief periods of intense exercise. Slower carbohydrates (lower numbers) could be used before long periods of exercise as well as after to help prevent delayed onset hypoglycemia.

 

However it may not be as easy as it sounds. The actual glycemic (blood sugar) impact of a given food depends not just on its glycemic index value but on preparation method and cooking time, the amount eaten, and what other foods are eaten at the same time (such as proteins and fats). It is important to remember that glycemic index tables are an average of the glycemic response of many individuals. For this reason I usually recommend the table be used as a starting place and that with regular self monitoring of blood glucose and good note taking you can develop your own personal "glycemic index".
Here are some suggestions on how to how to get started.

  • Eat whole grain, pumpernickel and oat bran bread more often than white bread.
  • Eat pasta, sweet potato or beans more often than mashed or instant potatoes.
  • Experiment with using foods such as rice cakes, corn flakes or white bread and jam for snacks prior to a short, intense workout.
  • iSee if snacking on fruits, milk or yogurt, or whole grain breads help to sustain your blood sugars through longer exercise periods. Try them as after exercise snacks as well.

Good luck and I'd love to hear about your experiences.

References :

  1. Whitham, D. and Hamilton, T. (2000). The Index in Depth.
  2. Diabetes Dialogue. Spring 2000. Canadian Diabetes Association.
  3. Wolever, TMS. (1997). The glycemic index : flogging a dead horse ? Diabetes Care.; 20. 452 - 456.

Additional Reading :

·Powell, K.F. and Miller, J.B. (1995). International tables of glycemic index. American Jounal of Clinical Nutrition, 62, 871S - 93S.

Carbohydrates in human nutrition. Report of a Joint FAO/WHO Expert Consultation, Rome, 14 - 18 April, 1997, FAO Food and Nutrition Paper 66. Rome 1998.


Starch Foods
Glycemic Index (Bread = 100)
Lentils / kidney / baked beans 40 - 69
Sweet potato 54
Cereal-All bran 60
Pumpernickel 66
Parboiled rice 68
Bread-oat bran 72
Potato-mashed/boiled 104
Cereal-Corn Flakes 117
Rice cakes 123
Instant rice 124
Fruits and Vegetables
Plum 34
Grapefruit 36
Apple 52
Grapes 62
Green peas 68
Banana 76
Carrots 101
Watermelon 103
Milk Products
Yogurt-artificially sweetened 20
Milk-skim 46
Yogurt-low fat, sugar sweetened 47
Miscellaneous
Power Bar 30- 35 *
Ice cream 87
White sugar 83
Pop 97
Lifesavers 100

*Info provided by Power Bar Company


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