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The Glycemic Index: A Primer for Family Physicians

The Glycemic Index: A Primer for Family Physicians. Dr. Julia Rackal Dr. Aisha Lofters St. Michael's Hospital Department of Family & Community Medicine Toronto, ON. Outline. Background on Glycemic Index Quiz Time! So What's The Evidence? Implications For Food Labelling

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The Glycemic Index: A Primer for Family Physicians

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  1. The Glycemic Index: A Primer for Family Physicians Dr. Julia Rackal Dr. Aisha Lofters St. Michael's Hospital Department of Family & Community Medicine Toronto, ON

  2. Outline Background on Glycemic Index Quiz Time! So What's The Evidence? Implications For Food Labelling Working Through A Case Resources Final Questions

  3. Rationale • Success of advocating ‘low fat diet’ has been minimal” – increasing prevalence of obesity and diabetes. • Technological advances in food processing and increased dependence on convenient, instant, and precooked foods – faster and faster rates of digestion and absorption.

  4. What is the Glycemic Index? The glycemic index, or GI, is a relatively new measure but it has quickly become popular as a dietary tool The GI is a tool that helps us differentiate between the various carbohydrates we eat and how our bodies use them Measures how quickly we digest and absorb carbohydrates and ranks foods accordingly

  5. What is the Glycemic Index? Carbohydrates that break down quickly, release glucose rapidly into the bloodstream have a high GI Conversely, those that break down more slowly, release glucose more gradually have a low GI A concept developed by Dr. David Jenkins and colleagues in 1980 at St. Michael's Hospital, University of Toronto while trying to find foods best for diabetics

  6. What is the Glycemic Index? Slowing carbohydrate absorption through a low G.I. diet has advantages in diabetes prevention and treatment A low G.I. diet has a similar mechanism of action as the medication, acarbose, which inhibits digestion of carbohydrates

  7. How Is The G.I. Calculated? Low = provide sustained energy, glucose does not rise very high for very long Low = 55 or less, 70 or less depending on the system (white bread vs. glucose) Intermediate 55-70 vs. 70-100 High = glucose goes higher for longer High = 70 or more vs. 100 or more

  8. Some Low G.I. Foods - Steel cut oats - Barley - Pasta - Parboiled rice - Lentils - Chick peas - Dried beans - Pumpernickel breads - Quinoa

  9. What Is Glycemic Load? Glycemic load = glycemic index x actual amount of available carbohydrates consumed Reminder that serving size is still important! Low G.I. but a very large serving = high glycemic load Total carb intake is a primary factor in glycemic response of a meal

  10. Important Points to Remember The glycemic index is affected by: -type of food -its ripeness -processing -length of storage -cooking methods

  11. So, What's The Evidence? A lower G.I. diet has been associated with: Lower HbA1C Higher HDL Lower CRP

  12. So, What's The Evidence? But has glycemic index been associated with important clinical outcomes? Myocardial infarctions CHD Type 2 diabetes Gallbladder disease Breast cancer

  13. Resources Gallop Rick (Dec 2009) The GI Diet, Revised: The Green Light Way to Permanent Weight Loss: Revised and Updated. Random House Canada Brand-Miller J, Wolever T, Colagiuro S, Foster-Powell (Dec 2006) The Dietary Solution for Lifelong Health. 3rd Ed. Da Capo Press GI News, The Official Glycemic Index Newsletter – emailed monthly to subscribers - http://ginews.blogspot.com/

  14. References - Websites 1. The GI Symbol Program, www.gisymbol.com 2. How to Calculate Glycemic Index and Glycemic Load, www.glycemicgourmet.com/how-calculate-glycemic-index.html 3. Glycemic Index, www.en.wikipedia.org/wiki/Glycemic_Index 4. GI News, The Official Glycemic Index Newsletter 5. The Glycemic Index – Canadian Diabetes Association, www.diabetes.ca/for-professionals/resources/nutrition/glycemic-index

  15. References • Barclay, A. W., Petocz, P., McMillan-Price, J., Flood, V. M., Prvan, T., Mitchell, P., et al. (2008). Glycemic index, glycemic load, and chronic disease risk--a meta-analysis of observational studies. American Journal of Clinical Nutrition, 87(3), 627-637. • Barclay, A. W., Petocz, P., McMillan-Price, J., Flood, V. M., Prvan, T., Mitchell, P., et al. (2008). Glycemic index, glycemic load, and chronic disease risk--a meta-analysis of observational studies. American Journal of Clinical Nutrition, 87(3), 627-637. • Berra, B., & Rizzo, A. M. (2009). Glycemic index, glycemic load: New evidence for a link with acne. Journal of the American College of Nutrition, 28(Suppl), 450S-454S. • Brand-Miller, J., McMillan-Price, J., Steinbeck, K., & Caterson, I. (2009). Dietary glycemic index: Health implications. Journal of the American College of Nutrition, 28(Suppl), 446S-449S. • Buyken, A. E., Mitchell, P., Ceriello, A., & Brand-Miller, J. (2010). Optimal dietary approaches for prevention of type 2 diabetes: A life-course perspective. Diabetologia, 53(3), 406-418. • Jakobsen, M. U., Dethlefsen, C., Joensen, A. M., Stegger, J., Tjonneland, A., Schmidt, E. B., et al. (2010). Intake of carbohydrates compared with intake of saturated fatty acids and risk of myocardial infarction: Importance of the glycemic index. American Journal of Clinical Nutrition, 91(6), 1764-1768. • Levitan, E. B., Cook, N. R., Stampfer, M. J., Ridker, P. M., Rexrode, K. M., Buring, J. E., et al. (2008). Dietary glycemic index, dietary glycemic load, blood lipids, and C-reactive protein. Metabolism: Clinical & Experimental, 57(3), 437-443.

  16. References cont. • Levitan, E. B., Mittleman, M. A., & Wolk, A. (2010). Dietary glycaemic index, dietary glycaemic load and incidence of myocardial infarction in women. British Journal of Nutrition, 103(7), 1049-1055. • Liljeberg, H.G., A.K. Akerberg, and I.M. Bjorck. Effect of the glycemic index and content of indigestible carbohydrates of cereal-based breakfast meals on glucose tolerance at lunch in healthy subjects. Am J Clin Nutr.69(4):647- 55,1999. • Mondazzi, L., & Arcelli, E. (2009). Glycemic index in sport nutrition. Journal of the American College of Nutrition, 28(Suppl), 455S-463S. • Sieri, S., Krogh, V., Berrino, F., Evangelista, A., Agnoli, C., Brighenti, F., et al. (2010). Dietary glycemic load and index and risk of coronary heart disease in a large italian cohort: The EPICOR study. Archives of Internal Medicine, 170(7), 640-647. Thomas D, et al. Low glycaemic index or low glycaemic load diets for overweight and obesity. Cochrane Database of Systematic Reviews 2007, Issue 3. Art. No.: CD005105. DOI: 10.1002/14651858.CD005105.pub2. • Wolever, T. M., Gibbs, A. L., Mehling, C., Chiasson, J. L., Connelly, P. W., Josse, R. G., et al. (2008). The canadian trial of carbohydrates in diabetes (CCD), a 1-y controlled trial of low-glycemic-index dietary carbohydrate in type 2 diabetes: No effect on glycated hemoglobin but reduction in C-reactive protein. American Journal of Clinical Nutrition, 87(1), 114-125. • Wolever, T.M., D.J. Jenkins, A.M. Ocana, V.A. Rao, and G.R. Collier. Second-meal effect: low-glycemic-index foods eaten at dinner improve subsequent breakfast glycemic response. Am J Clin Nutr.48(4):1041-7,1988.

  17. Acknowledgements Thanks to Dr. Rick Gallup and Dr. David Jenkins for their input and contribution to this presentation! Some slides contributed by Dr. David Jenkins

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