The pros and cons of carbohydrate intake in modern Australia and New Zealand an overview of their health effects

Transcription

1 The pros and cons of carbohydrate intake in modern Australia and New Zealand an overview of their health effects ILSI and GLNC seminar 19 March 2013 Peter Williams PhD FDAA Visiting Principal Fellow, University of Wollongong Adjunct Professor Nutrition & Dietetics, University of Canberra

2 Major types of dietary carbohydrates Class (Degree of polymerisation) Sub-Group Components Sugars (1-2) Monosaccharides Glucose, galactose, fructose Disaccharides Polyols Sucrose, lactose, trehalose Oligosaccharides (3-9) Malto-oligosaccharides Maltodextrins Other oligosaccharides Sorbitol, mannitol, lactilol, xylitol, isomalt, maltilol Raffinose, stachyose, polydextrose, fructo-oligosaccharides Polysaccharides (>9) Starch Amylose, amylopectin, modified starches Non-starch polysaccharides Cellulose, hemicellulose, pectins, arabinoxlans, β-glucans, glucomannans, gums, hydrocolloids

3 Other Classifications Simple Sugars intrinsic sugars extrinsic or added sugars Complex oligo-saccharides polysaccharides Available CHO sugars most starch Unavailable CHO oligo-saccharides resistant starch non-starch polysaccharides Dietary Fibre = Unavailable CHO + lignin

4 Components of Dietary Fibre Total Dietary Fibre total non-starch polysaccharides resistant starch lignin soluble NSP insoluble NSP cellulose + lignin = Crude Fibre pectins gums, mucilages non-cellulosic NSP cellulose

5 Functions of Carbohydrate Energy for all cells Provides 17kJ/g (4Cal/g); approx same as protein and half that of fat(37kj/g) or alcohol (29kJ/g) Blood glucose fuel for nervous system, red blood cells Laxation Fermentable substrate in bowel (energy and prebiotic) Satiety Flavour (sweetness) Bulking Preservative

6 Digestion of Carbohydrate

7 Percentage energy from carbohydrate

8 Food Sources of Carbohydrate High Carbohydrate Foods (>70% energy) pasta, rice, bread, flour, sugar, fruits, vegetables Moderate Carbohydrate foods (20-70% energy) cakes, pastries, pizza, nuts, chocolates, milk, beer Low Carbohydrate foods (<20% energy) meat, fish, margarine, eggs, cheese, wine and spirits

9 Intake of CHO in various countries Country % Energy from CHO Greenland 38 Netherlands 42 USA 47 China 59 PNG 62 Malawi 79 Sources: Mann & Truswell Essentials of Human Nutrition 2012 Bang et al Am J Clin Nutr 1980:33:2657

10 Australian and NZ intakes Australia 1995 New Zealand 2008/9 Mean adult intake 255g/d 251g/d Energy from CHO 46% 47% Energy from sugars 21% 20% Energy from starch 25% 27%

11 Trends in Australian apparent %E CHO Source: ABS Apparent consumption of foodstuffs

12 Food sources of CHO (1995 Australian NNS; 2009 NZ ANS) Food Australia % CHO E New Zealand % CHO E Cereals and cereal products Cereal-based dishes Non-alcoholic beverages 11 8 Vegetables 9 13 Fruit 8 10 Milk and dairy 8 7 Sugar & confectionery 8 7 Meat 2 3 Alcoholic beverages 2 2 Other foods 4 3 Total

13 Recommended CHO intakes Source USA (2002) WHO (2003) NHMRC (2006) EFSA (2010) Diabetes Australia (2012) EAR: 100g/d RDA: 130g/d Total CHO: 55-75%E Free sugars: <10%E AI for infants only 7-12m: 90g/d SDT: 45-65%E predominantly low energy density and low GI food sources 45-60%E Up to 50%E One low GI choice per meal

14 Labelling Carbohydrate Carbohydrate on labels is calculated by difference, not measured by analysis: CHO = Total - (Water+Protein+Fat+Ash) CHO includes sugar + starch + dietary fibre Energy value uses 17kJ/g for total CHO, but 8kJ/g for fibre Sugars mandatory declaration; fibre optional

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16 Food Standard Nutrition, Heath & Related Claims Carbohydrate Reduced/light at least 25% less than reference food Increased at least 25% more than reference food Fibre Source/Contains 2g/serve Good source/high 4g/serve Excellent source/very high 7g/serve Increased 2g/serve and 25% more

17 Food Standard Nutrition, Heath & Related Claims Glycemic Index Low 55 Medium High 70 Sugar Free/Low Sugar <5% sugar (2.5% in liquid) Reduced/Light at least 25% less than reference food No added sugars no sugar, honey, malt or deionised juice, but can be artificially sweetened Unsweetened no artificial sweeteners

18 Pros and Cons PRO Cheap and sustainable Athletic performance Prebiotic effect Wholegrain reduces CVD risk Dietary fibre reduces bowel cancer risk CON Obesity Dental caries CHO intolerances (eg lactose) Insulin resistance High triglycerides; low HDL

19 Carbohydrate energy is cheap Food % E from CHO $/1000kJ* Chicken thighs Peas Low fat yoghurt Baked beans White bread Bananas White rice Strawberry jam * Based on Coles online prices March 2013

20 CSIRO estimate of proportion of food-related greenhouse gas emissions in the average Australian diet

21 Fibre improves large bowel function Reduced transit time (bran & cellulose; not soluble fibres) Increased stool weight and frequency US Male Health Professionals Study found insoluble fibre, esp cellulose, reduces risk of diverticular disease RR=0.55 (23g vs 10g/d) (Aldoori et al J Nutr 1998;128: )

22 Cholesterol-lowering effects Meta-analysis of 67 trials found: soluble fibre intakes of 2-10g/d lower total and LDL cholesterol (up to 18%) Most effective sources are oats, psyllium, pectin and guar gum (Brown et al Am J Clin Nutr 1999;69:30) US Health Professionals study found 29% reduction in CHD risk for every 10g increase in cereal fibre (Rimm et al JAMA 1996;275:447). Nurses Health study found only cereal fibre (not veg or fruit) was effective (Wolk et al JAMA 1999;281:1998)

23 Satiety and weight control Satiety scores correlate with fibre content (Holt et al Eur J Clin Nutr 1995;49:675) Obesity is associated with a low fibre intake (Alferi et al Obes Res 1995;3:541) Higher fibre foods take longer to eat decrease the energy density of a meal slow gastric emptying affect some gastrointestinal hormones regulating food intake

24 Fibre and bowel cancer Dietary fibre might reduce risk of bowel cancer through lowering ph production increased transit time World Cancer Research Fund Update on Colorectal Cancer (2011): Updated meta-analysis shows: 10% reduced risk per 10g/d Now Convincing evidence that food containing dietary fibre decreases risk

25 Childhood Obesity in Australia Booth et al Am J Clin Nutr 2003; 77: Percentage of 7-15 year olds overweight or obese Boys Girls

26 Increasing energy intake from CHO food % Change Boys ,670kJ 11,088kJ +14.6% Girls ,586kJ 8,488kJ +11.9% Increases in energy intake were attributable mainly to an increased intake of carbohydrate from a range of foods including cereals and cereal-based foods, confectionery, non-alcoholic beverages, and sugar products Source: Australia s Health 2002

27 Dental caries Moynihan Bull WHO 2005;83:694 All fermentable carbohydrates (especially high GI sources) can be broken down by bacteria in the mouth to produce acid that increases the risk of caries, but sugar consumption, particularly between meals, increases risk significantly. Risk depends on frequency of food type, consumption frequency, oral hygiene, fluoride, and genetic factors. Risk is low when free sugar consumption <15Kg/person/year (40g/d) Eat for Health (2013): Consumption of soft drink is associated with increased of dental caries in children (Grade C)

28 Lowered nutrient availability No significant effect of fibre on vitamin absorption Inhibition of absorption of some minerals (Ca, Fe, Cu, Zn) at high fibre intakes - over 50g/d No convincing evidence of detrimental effects when consumed at high amounts from natural sources (up to 50g/d)

29 Lactose intolerance Low lactase levels in 75% of world adults over 3 years (Caucasians are an exception) Symptoms: pain, gas, diarrhoea Often can tolerate low amounts (eg, 100mL milk with 5 g lactose) Yoghurt and cheese have low lactose levels Low lactose milks and soy beverages tolerated

30 Adjusted risk ratios for all-cause mortality associated with low-carbohydrate diets. Noto H, Goto A, Tsujimoto T, Noda M (2013) Low-Carbohydrate Diets and All-Cause Mortality: A Systematic Review and Meta- Analysis of Observational Studies. PLoS ONE 8(1): e doi: /journal.pone

31 Conclusions Very low CHO diets may be associated with health risk The Japanese, with the longest lifespan in the world, consumed approx 63%E as CHO in 2000 (Motsuda-Inoguchi et al Pub Health Nutr 2004;77:901) Current CHO intakes in Australia and New Zealand are at the lower end of international recommendations. Not all CHO is the same and food-based evidence is best to guide dietary recommendations The new Australia dietary guidelines promote consumption of many high CHO foods - especially wholegrain and high fibre cereals, vegetables, fruit and legumes - and discourage intake of foods and drinks with added sugars (especially soft drinks, cordials and energy drinks)