Scien&fic Basis for Communica&ng Carbohydrate Quality Glycemic Effect of Carbohydrate Containing Foods.

Transcription

1 Scien&fic Basis for Communica&ng Carbohydrate Quality Glycemic Effect of Carbohydrate Containing Foods. Thomas MS Wolever, MA, PhD, DM (Oxon) Department of Nutritional Sciences, University of Toronto, Toronto, ON, Canada. Keenan Research Centre of Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, ON, Canada. Glycemic Index Laboratories, Inc. 20 Victoria St., Suite 300, Toronto, ON, Canada.

2 FACULTY/PRESENTER DISCLOSURE Faculty/Presenter: Thomas Wolever RelaAonships with commercial interests: - Grants/Research Support: NONE - Speakers Bureau/Honoraria/Consulting Fees: - None in last 3 years - Other: - My wife and I are employees & part owners of: - GI Labs, Inc.

3 MITIGATING POTENTIAL BIAS Conflicts of interest always disclosed. Neither we nor GI Labs own any IP related to any research conducted. We have divested ourselves of financial interest in any company: From whom I have received honoraria or consulting fees Which has done business with GI Labs

4 Objectives Review scientific evidence for the utility of GR, GL and GI for communicating carbohydrate quality. Application to foods and meals Application to people with and without diabetes

5 Glycemic Response Plasma Glucose (mmol/l) n=14 % difference * * * ns incauc netauc 0-60min 0-120min 0-180min Time over which AUC calculated * ns Time (min)

6 GL = g GI/100 Units = g Glycemic Load GR elicited by GL grams of glucose Not a measure of carbohydrate quality Can be changed by altering amount or GI of carbohydrate. PracAcal applicaaon unclear GL of 1 Apple GL of 2 Apples g GI/ = = 17.6 (g GI/100)/1000Kcal 93 93

7 g GI/100 not proporaonal to GR Glucose Incremental AUC (mmol min/l) 300 Starchy Foods Sugars Glycaemic Load

8 g GI/100 not proporaonal to GR Relative Response (50g Glucose = 100%) Glucose Potato WB #1 WB #2 Sucrose Spaghetti Barley Fructose Grams Carbohydrate avcho GI RGR GL Potato 25g Pasta 50g RR = 1.49 GI (1-e g ) (r 2 = 0.962)

9 GL GR elicited by GLg glucose Relative Response (50g Glucose = 100%) Glucose Potato WB #1 WB #2 Sucrose Spaghetti Barley Fructose Potato: 119 Barley: 54 With 200g CHO RGR GL g glucose Grams Carbohydrate RR = 1.49 GI (1-e g ) (r 2 = 0.962) Maximum RGR = 1.49 GI

10 Diabetes Wolever et al 1994 Normal Christensen et al Normal Jenkins et al Glycemic load: Not a measure of CHO quality Not an accurate measure of glycemic response

11 Glycemic Index (GI) Food GI = 100 Glucose

12 Does the GI of foods depend on glucose tolerance status?

13 AUC (mmol min/l) Variance ( 10 6 ) Partitioning of variance AUC Within-subjects Between-subjects Food GI AUC GI Glycemic Index (%)

14 Can the GI of foods be measured precisely?

15 Between- Lab Precision: GR vs GI Between-Lab Mean SD p= CV p=

16 Can GI be applied to Mixed Meals? n=1 Meal GI = {ΣGI n g n }/G x Where, for x foods in the meal: GI n is the GI of the nth food; g n is the amount of avcho from the nth food; G is the amount of avcho in the entire meal. Proportional to glycemic response for meals with same macronutrient composition. Collier et al. Am J Clin Nutr 1986;44:349.

17 Meals containing different amounts of Carbohydrate, protein and fat 5 meals: Energy: Kcal Carb: g (33-69% en) Protein: 12-25g (11-20% en) Fat: 8-24g (15-47% en) Meal GI: Wolever & Bolognesi J Nutr 1996

18 Measuring the GI of Mixed Meals Flint et al. Brit J Nutr 2004;91:979 Predicted = dark bars; Measured = light bars

19 Flint et al. Brit J Nutr 2004;91:979 ComposiAon of Test Meals Wolever & Bolognesi, 1996 Flint et al., 2004 Energy (Kcal) Protein, Fat,CH 2 O, GI 0 Energy Protein (g) Fat (g) CH 2 O (g) GI (%) 0

20 Effect of adding protein and fat to CHO PROTEIN Slope: % reducaon per g/g All: (orange line) 86% FAT Slope: % reducaon per g/g Dairy fat: (dark green line) 70% Vegetable fat: (red line) 75%

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22 Recorded ComposiAon of Breakfast: Mean (range) Energy (Kcal) 400 ( ) Protein (g) 17 (3-43) Fat (g) 7 (1-28) Available carbohydrate (g) 67 (16-222) Dietary fiber (g) 9 (0-56) Glycemic Index 60 (37-85)

23 Summary of Evidence for GR, GL & GI Glycemic response Not a marker of CHO quality Glycemic load Not a marker of CHO quality Not an accurate measure of glycemic response Glycemic Index A marker of CHO quality Value does not depend on carbohydrate tolerance ISO standard method which is accurate and precise GI is measured in and a property of CHO-rich foods fed alone GI of mixed meals is calculated (not measured) GI is an independent determinant of the glycemic response elicited by mixed meals.

24 In the finish chute at The Icebreaker Hamilton, Ontario December 4, 2016 The End