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Topic 4- Carbohydrates

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KIN 346
Rhonna Hanning

Topic 4: Carbohydrates –Sugars, Starch, & Fibres Introduction to Carbohydrates – Primary role is to supply body with energy – Primary sources includes: grains, legumes, fruits & vegetables, dairy – Divided into categories based on # of sugar units they contain – DRI: ○ 130 g/day minimum recommendation ○ 45-60% of energy Simple Carbohydrates – The simple CHO include: ○ Monosaccharides (single sugars) ○ Disaccharides (two bonded sugars) – Monosaccharides are composed of 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms represented by the chemical form6l12C6H O (CHO) Monosaccharides – The monosaccharides: ○ Glucose –serves as the essential energy source for the body ○ Fructose –is the naturally occurring sugar found in fruits and honey ○ Galactose –binds with glucose to form milk sugar (lactose) 1 Disaccharides – Composed of pairs of monosaccharides all containing glucose – Glucose + glucose = maltose – Glucose + fructose = sucrose – Glucose + galactose = lactose Added Sugars – DRI added sugars - <25% of energy ○ WHO, CDA recommend <10% of energy – Added sugars include: white sugar, brown sugar, raw sugar, corn syrup solids, high-fructose corn syrup, malt syrup, maple syrup, pancake syrup, fructose sweetener, liquid fructose, honey molasses, dextrose – Leading source of added sugars in the diet –soft drinks ○ Soft drinks –regular 14.3% ○ Milk – 14% ○ Fruit – 10.6% ○ Confectionery – 10.3% ○ Fruit juice – 9.2% – Trends: ○ Male teenagers (14-18yrs) consume most amount of sugars in Canada  Average intake 41 teaspoons of sugar per day ○ Males > females ○ Canadians on average consume 110 grams of sugar per day Complex Carbohydrates – Polysaccharides –large molecules composed of chains of monosaccharides ○ Includes:  Glycogen and starch –provide a storage form of glucose  Fibre –provides structure to plant foots Glycogen – Glucose that is not needed immediately for energy is stored in the body as glycogen 2 – Stored in the liver and muscle in highly branched chains which allow for the quick release of energy when it is needed Starch – Starch is composed of long chains of glucose molecules –derived from plant foods – Primary sources include: grains, potatoes, and legumes Fibre – Fibres are polysaccharides but differ from starches in that their bonds cannot be broken down by digestive enzymes –nondigestible – Soluble –dissolves in water & forms gels ○ E.g., gums, pectin – Insoluble –does NOT dissolve in water or form gels ○ E.g., cellulose – Resistant starches –starches that escape digestion and absorption in the small intestine – DRI: ○ Females – 19-50 years: 25g/day ○ Males – 19-50 years: 38g/day ○ Current intakes:  Males ~ 17g/day  Females ~ 13g/day ○ WHO –recommends an upper limit of 40g/day ○ Why?  Too much fibre: • May prevent those with small capacity from meeting energy needs • GI distress • May interfere with mineral absorption 3 4 Carbohydrate Absorportion Health Effects of Carbohydrates – Varies with CHO source (e.g., content of fibre and other nutrients) – Excess consumption of simple “added” sugars can be harmful by: 1) Displacing intake of important nutrients 2) Cavities –sugar stimulates bacterial acid production and erosion of tooth enamel 3) Contributing to obesity High Soft Drink Consumption Among Teenagers – Diet high in soft-drinks are associated with: ○ Low nutrient dense foods ○ Low intake of milk and fruit juice  Low intakes of calcium, vit D, magnesium, and phosphorous  Important stage for bone mineralization –attainment of peak bone mass ○ Low intakes of other nutrients including iron, zinc, riboflavin, folate, B6, vit A & C – Some evidence that caffeine and acids in soft drinks may produce bone demineralization 5 Fibre – Fibre remains in GI tract –fibre is not absorbed – Fibre plays an important role in: ○ Diabetes  Soluble fibre –slows rate of glucose absorption –blood glucose control ○ Gastrointestinal Health  Increase fecal bulk –prevents constipation, hemorrhoids, and diverticulitis ○ Colon cancer? ○ Weigh management –decrease energy density, increase satiety ○ Cardiovascular disease  Soluble fibre –decrease total cholesterol –binds with bile acids (made from cholesterol) in the intestine and increases excretion Diabetes Maintenance of Blood Glucose – Body needs a continuous supply of glucose – Body maintains constant level of blood glucose which circulates and delivers glucose to the tissues and organs – Blood glucose is regulated by insulin and glucagon hormones produce by the pancreas – Fig 4.12 –normal fasting blood glucose ~4-6.1mmol/L Diabetes – Complex metabolic disorder –insufficient production or utilization of insulin – Inability to absorb, transport, and utilize glucose – Glucose builds up in the blood stream instead of being used for energy 6 – Complications of diabetes are associated with long term exposure to hyperglycemia Numbers of People with Diabetes (in millions) in 2000 and 2010 Type 1 vs. Type 2 – Type 1 –B cells of the pancreas produce too little or no insulin –autoimmune mechanics, virus? – Type 2 –insulin resistance –occurs when the body is no longer sensitive to the presence of insulin ○ Risk factors include: obesity, age, ethnicity, genetics – Diagnosis is made on the basis of: ○ Fasting blood suga≥ 7.0mmol/L ○ Oral glucose tolerance t≥11.1mmol/L Increasing Prevalence of Type 2 in US with Increasing Consumption of Refined CHO 7 DiabetesandCarbohydrateConsumption 525
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