Poten&al new health claims for barley: Reduc&on in Post-Prandial Glycaemic Response

Transcription

1 Poten&al new health claims for barley: Reduc&on in Post-Prandial Glycaemic Response Dr. Heather Blewe? 1,2,3,4 and Dr. Nancy Ames 1,3 1 Morden Research and Development Centre, Agriculture and Agri-Food Canada, Winnipeg, MB. 2 Canadian Centre for Agri-Food Research in Health and Medicine, St. Boniface Research Centre, Winnipeg, MB. 3 Department of Human Nutri&onal Sciences, University of Manitoba, Winnipeg, MB. 4 Department of Physiology and Pathophysiology, University of Manitoba, Winnipeg, MB.

2 Background Diabetes is one of the most common chronic diseases affec&ng Canadians Diabetes is characterized by blood sugar [] AUer a carbohydrate rich meal, blood sugar Length of &me & peak response depends in part on the composi&on of the food post-prandial glycaemic response 2% may be beneficial, if post-prandial insulinaemic responses do not

3 Glycemic Index (GI) GI is a scale that ranks CHO-rich foods by how much they raise blood glucose levels compared to glucose or white bread. Low GI= <55 Medium GI = High GI = >7 Canadian Diabetes Associa&on Clinical Prac&ce Guidelines recommend people with diabetes replace high-gi foods with low-gi foods to improve glycemic control.

4 GI protocol Fas&ng blood sample taken. Volunteer consumes 5 g of available CHO in test food Blood samples collected at 15, 3, 45, 6, 9, 12 min. Glucose values are plo?ed; iauc calculated mmol/l minutes

5 GI protocol con&nued Same procedure repeated with 5 g glucose or white bread. (iauc test food iauc reference food) 1 = GI Average GI of 1 volunteers = GI of test food

6 Ra&onale Barley is considered a low GI grain, but factors can be manipulated to op&mize the glycemic response: Type of starch: Amylose has &ghtly packed structure = resistant to diges&on. Amylopec&n has branched structure = easier to digest. Amount/type of fibre: Fibre resists diges&on. Soluble fibre forms a gel-like structure. Insoluble fibre increases bulk.

7 A double blind, randomized, controlled trial Bri%sh Journal of Nutri%on (215), 113, Principal Inves&gator: Dr. Nancy Ames (AAFC) Clinical Trial: Dr. Carla Taylor & Dr. Peter Zahradka (CCARM) Objec&ve Develop food products using barley that provide 5g of available CHO per serving, but vary in levels of: Amylose (resistant starch) β-glucan (soluble fibre) Insoluble fibre Test post-prandial glycaemic response in a human trial.

8 Barley tor&lla development Tor&llas selected as test food. Ingredients: Barley flour and water. Different genotypes and milling frac&ons were tested. Total starch, resistant starch, total fibre, β-glucan, insoluble fibre. Special flour blends used to prepare 5 different types of tor&llas: 1. Low vs. high amylose 2. Low vs. medium vs. high β-glucan 3. Low vs. high IDF

9 Barley tor&lla development -RCFFN Tor&llas were prepared and frozen. Re-hea&ng and presenta&on protocol was developed.

10 Low vs. high amylose (low) HA-DFF (high) Total starch (g) Resistant starch (g) Total dietary fibre (g) Insoluble dietary fibre (g) β-glucan (g) Protein (g) Available carbohydrates (g) 5 5 # tor&llas/serving Fibar = low amylose; SH9925 = high amylose = wholegrain flour; HA-DFF= high-amylose dusted flour frac&ons

11 Low vs. medium vs. high β-glucan SGF (low) (med) BF-BG (high) Total starch (g) Resistant starch (g) Total dietary fibre (g) Insoluble dietary fibre (g) β-glucan (g) Protein (g) Available carbohydrates (g) # tor&llas/serving SGF=straight grade flour; = wholegrain flour; BF-BG= bran flour with high β-glucan

12 Low vs. high insoluble fibre BF-IDF Total starch (g) Resistant starch (g) Total dietary fibre (g) Insoluble dietary fibre (g) β-glucan (g) Protein (g) Available carbohydrates (g) 5 5 # tor&llas/serving = wholegrain flour; BF-IDF= bran flour with high insoluble fibre

13 Par&cipants Healthy men and women n=12 (n=7 male; n=5 female) Age 18-4; BMI visits to consume the 5 different tor&llas and glucose drink in random order. Blood collected at fas&ng, 15, 3, 45, 6, 12, 18 min Outcome measures: glucose, insulin

14 Plasma Insulin (pmol/l) Low vs. high amylose: no effect on glucose, insulin or GI Plasma Glucose (mmol/l) # 3 # # 45 # 45 6 # 6 12 Time (min) # Time (min) 12 HA-DFF 18 HA-DFF 18 iauc (pmol/lmin) HA-DFF Medium GI Low GI

15 Plasma Insulin (pmol/l) Low vs. med vs. high β-glucan: high β-glucan = glucose, insulin and GI Plasma Glucose (mmol/l) a a b 45 a ab b 6 a c c b ^ ^ ^ ^ a Time (min) a b b ab 12 SGF BF-BG 18 SGF BF-BG iauc (mmol/lmin) iauc (pmol/lmin) a SGF a ab b b BF-BG c Glycemic Index a SGF a Medium GI Low GI b BF-BG Time (min) SGF BF-BG

16 Plasma Insulin (pmol/l) Low vs. high IDF: No effect on glucose, insulin or GI Plasma Glucose (mmol/l) a b Time (min) BF-DF BF-IDF iauc (mmol/lmin) iauc (pmol/lmin) BF-IDF Glycemic Index Medium GI BF-IDF Low GI Time (min) BF-IDF

17 Conclusions Amylose Although, Low amylose tor&llas= medium GI High amylose= low GI Amylose content of barley tor&llas not important when designing func&onal foods with low post-prandial glucose responses. β-glucan Tor&llas with the highest β-glucan content had the lowest post-prandial glucose and insulin responses in healthy adults. β-glucan content of barley flour can be varied during processing. IDF Low vs. high IDF did not alter glucose or insulin response. Overall Barley tor&llas are low GI foods. Processing methods can be used to op&mize barley containing func&onal foods to reduce post-prandial blood glucose responses. Poten&al to develop func&onal foods for popula&ons at risk of diabetes.

18 Health Canada s guidance doc on health claims PPGR Don t use GI Not precise enough for labeling purposes Does not take into account serving sizes Not consistent with na&onal nutri&onal guidelines Studies need to show the following: 2% decrease in PPGR Glucose and insulin measurements Healthy volunteers Reference food should be similar to the test food (including in total fibre, macronutrient and energy profile) Appropriate serving size

19 European Food Safety Authority (EFSA) approved health claim 4g of β-glucan from oat or barley for each 3g AC will reduce PPGR. All had >2% reduc&ons in PPGR compared to glucose, but the max reduc&on was seen with the highest β- glucan dose. Need a dose response study:, 2, 4, 6 g β-glucan/ 3g AC

20 Waffle nutrient composition TDF (g) IDF (g) Oil (g) Protein (g) BG (g) AC (g) Serving size (g) Typical waffle Control-wheat matching composition g BG g BG g BG

21 Acknowledgements Investigators Nancy Ames (PI) Carla Taylor (PI: clinical trial) Peter Zahradka (Co:PI: clinical trial) Brian Rossnagel (developed & provided barley varieties) Test product development team Members of Nancy Ames research group at the CRC Clinical Team Angela Wilson, Brenda Wright, Danielle Stringer, Alanna Baldwin Study Participants Funding was provided by the Alberta Barley Commission (tortilla study) and Agriculture and Agri-Food Canada (waffle study)

22 Data Analysis Glucose =Colorimetric assay from Genzyme Diagnos&cs Insulin= Ultrasensi&ve ELISA from Alpco Diagnos&cs Sta&s&cal analysis using SAS (9.2) AUC=Paired T-tests or Proc mixed with tor&lla as fixed effect and subject as random variable. Time= Proc mixed repeated measures. Differences among means determined by Lsmeans (p<.5)