A role for kiwifruit in managing blood glucose John Monro, Plant & Food Research Host Institution
Plan of talk » Measuring the properties of kiwifruit that could be beneficial » Testing the role of kiwifruit properties in clinical trials » Measuring the glycaemic potency of kiwifruit » Exchanging kiwifruit for other carbohydrate foods – glycaemic and nutritional consequences » Next steps – the HVN/Zespri phase
Aim » Help Zespri to sell kiwifruit in an increasingly diabetic, sugar averse market, by showing that they are safe and healthy Project funding » HVN $1 million over 3 years » Zespri $100,000 over 3 years
Problems and possibilities for kiwifruit » Market is becoming » Kiwifruit are a rich source fearful of sugars of vitamin C » Kiwifruit are sugar-rich » Kiwifruit may aid digestion » Kiwifruit sugars are about » Kiwifruit appear to 50% fructose (fruit sugar) stimulate laxation - fructose is bad news » Used the right way, kiwifruit may reduce glycaemia and protect against its effects
A problem and opportunity facing the kiwifruit industry » A “tsunami of diabetes” in the major markets for kiwifruit > 400 million diabetic by 2030 Best quality kiwifruit
Challenges » Showing that kiwifruit, even in the diets of consumers at risk for diabetes, are nutritionally beneficial – Short term (postprandial) – Long term (metabolic and diverse diabetic complications) » Incorporating kiwifruit into the diet in ways that lead to a net health benefit to consumers
Kiwifruit have favourable properties Residues occupied a large volume after digestion Kiwifruit settled bed volume increased about 4x after digestion 2 kiwifruit ↓ 900 ml disperse hydrated solids volume Stomach is distensible 50 (empty)-1500 ml Therefore dietary fibre dispersion from one or two kiwifruit, easily fills gastric space surrounding and interacting with other foods. Post-digestion volume per unit of pulp digested and settled overnight
Disperse kiwifruit cell wall remnants retarded processes involved in glycaemic response Digestion Luminal diffusion Luminal mixing Reduced rate of glucose absorption in vivo ? Altered postprandial blood glucose response?
Non-carbohydrate components of kiwifruit moderated glycaemic response in vivo Wheat biscuit + 2 kiwifruit (WB+KF), compared with Wheat biscuit + 2 kiwifruit’s sugars (WB+Sug) (n = 20) » Reduced amplitude » Sustained availability » No hypoglycaemia Means ± sem Conclusion: Non-carbohydrate components of kiwifruit may improve glucose homeostasis
Equal carbohydrate partial substitution of kiwifruit for starchy food reduced glycaemic response Incorporating KF into a diet without increasing carbohydrate or energy intake – the dietetic approach Mean blood glucose responses to equal (40 g) available Recommended limit carbohydrate meals: Glucose Wheat biscuit (WB), WB + ‘Hayward’ kiwifruit (WB+GR) WB + SunGold kiwifruit (WB+SG) Benefits confirmed
Areas within measurement periods showed improved glucose homeostasis SunGold and Hayward improved glycaemic response over 3 h. 0-180 min: (full period) LSD 26.8, p = 0.012, 0-120 min: LSD = 22.7, p <.001 120-180 min LSD = 11.5, p < 0.001
Relative glycaemic potency (RGP) Allows the glycaemic potency of a food to be expressed as grams of glucose equivalents (GGE) per 100 g food. The glycaemic effects of SunGold and Hayward were measured relative to a 40 g glucose reference. IAUC food /IAUC gluc x Wt Gluc /Wt food x 100 = RGP (g glucose equivts./100 g) = GGE/100 g
Kiwifruit has a low relative glycaemic potency (GGE/100 g) One kiwifruit had the same effect on blood glucose as 6.6 g glucose GGE per 100 g food (Means ± sem) (LSD = 4.9, p < 0.001)
Relative glycaemic impact expressed as a virtual food component (GGE (g) /given quantity) GGE per serving Relative glycaemic impact can be expressed in gram units, so behaves like a nutrient. Because it is expressed as if it were a nutrient, but represents an effect, it has been termed a virtual food component.
Potential role of GGE in showing relative glycaemic impact in food labels Kiwifruit Serving size – 100 g Per serving PER 100 g (Approx) Energy-kJ 202 202 Protein (g) 0.9 0.9 Fat (g) 0.6 0.6 Carbohydrate - Total 11 11 - Sugars 10 10 Dietary fibre (g) 2.3 2.3 Sodium (mg) 4 4 Potassium (mg) 236 236 Vitamin C (mg) 120 120 Β -carotene equiv. (µg) 18 18 Glycaemic impact (glucose equiv.) (g) 6 6 Relative glycaemic impact: LOW
Effect of equi-carbohydrate substitution by kiwifruit on estimated GGE dose Kiwifruit exchanges Serve GI CHOAVL GGE Exchange 1 KF Exchange 2 KF New New (g) (%) (g/serve) (g) GGE % Decr GGE % Decr Bread white 60 75 30 22.5 18.9 16 15.3 32 Cornflakes 30 80 25 20.0 15.8 21 11.5 43 Rice Bubbles 30 88 26 22.9 17.6 23 12.4 46 Rice, white (China) 150 83 36 29.9 25.3 15 20.6 31 Rice, Jasmine (Japan) 150 109 42 45.8 37.9 17 30.0 34 Rice, Japonica (Japan) 150 75 46 34.5 30.9 11 27.3 21 Mashed potato (China) 150 73 20 14.6 11.2 23 7.9 46 Sweet potato (China) 150 77 21 16.2 12.3 24 8.4 48 1 Kiwifruit 100 46 12.5 5.8 5.8 0 5.8 0 2 Kiwifruit 200 46 25 11.5 11.5 0 11.5 0 Difference between high and low GI is 15 %
Equal carbohydrate, partial exchange of whole kiwifruit for starchy staple improves nutrient intake Effect of partially replacing the available carbohydrate in starchy staple foods by the amount of available carbohydrate in one whole kiwifruit.
Timing of kiwifruit ingestion relative to carbohydrate food may be important SunGold kiwifruit consumed 30 min before wheat biscuit (WB) decapitated the blood glucose spike WB alone WB + SG together WB 30m post SG (40% less than WB) Equi-carbohydrate comparison
Kiwifruit has a role in appetite control during glycaemia management Kiwifruit-substituted Wheat Biscuit was as satiating as Wheat Biscuit alone at the same CHO intake
The HVN-Zespri phase (2016-2019) » With an emphasis on health claims the research will attend to MPI and EFSA criteria: » Consumer safety » Relevance to customary food consumption patterns » Plausible mechanisms » Relevant endpoints » Relevant biomarkers
Next steps: The HVN-Zespri phase Intake patterns for Metabolic effects of When to eat kiwifruit: clinical optimal effect long-term KF consumption (KRIP pilot study) Kiwifruit exchange tables (2016) (2016) Kiwifruit exchanges in realistic Long-term consumption Long-term consumption HVN European and Asian meals metabolic effects metabolic and risk factor effects (postprandial) (healthy) (prediabetic) (2016) (2017) (2018) » Consumer safety: Insulin response, fructose effects » Customary food consumption: Realistic meals, customary diets » Plausable mechanisms: Metabolic, hormonal, pancreatic, physiological-metabolic syndrome » Relevant endpoints: CVD, circulatory, β -cell function » Relevant biomarkers: Plasma lipids, glycation, oxidative stress, inflammation, endothelial dysfunction
Acknowledgements » Zespri » Carbohydrate Digestion and Metabolism Team, Plant & Food Research: » Kerry Bently-Hewitt » Sue Middlemiss-Krak » Suman Mishra » Jinny Willis, Don Bevan Centre, Christchurch » All participants in the clinical trials
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