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Carbohydrates
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Learning Outcomes Identify the major types of carbohydrates and give examples of food sources for each List alternative sweeteners that can be used to reduce sugar intake Describe recommendations for carbohydrate intake and health risks caused by low or excessive intakes List the functions of carbohydrates in the body
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Learning Outcomes Explain how carbohydrates are digested and absorbed
Explain the cause of, effects of and dietary treatment for lactose intolerance Describe the regulation of blood glucose, conditions caused by blood glucose imbalance, types of diabetes, and dietary treatment for diabetes Describe dietary measures to reduce the risk of developing type 2 diabetes
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Carbohydrates Composed of carbon, hydrogen and oxygen
Produced by plants via photosynthesis Simple carbohydrates Monosaccharides and Disaccharides Polysaccharides (more complex) Starch, Glycogen, and Fiber
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Monosaccharides Glucose Fructose Galactose
Blood sugar Fructose High-fructose corn syrup Galactose Part of lactose Sugar Alcohols (monosaccharide derivatives) Xylitol, mannitol and sorbitol Pentoses (5 carbon) Ribose and Deoxyribose
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Disaccharides Two monosaccharides linked by a condensation reaction
Alpha or beta C-O-C bonds connect them Maltose Glucose and Glucose; alpha bond Sucrose Glucose and Fructose; alpha bond Lactose Galactose and Glucose; beta bond
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Complex Carbohydrates
Oligosaccharides Contain 3-10 sugar units Raffinose and Stachyose Indigestible; bacterial fermentation – gas Polysaccharides Contain many glucose molecules Alpha or beta bond determine digestibility
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Digestible Polysaccharides
Starch (plants) Amylose: straight chain Amylopectin: branched Glycogen (animals) Storage form of glucose in human body Liver glycogen (90g): converted to blood sugar Muscle glycogen (300g): glucose for muscle use
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Indigestible Polysaccharides
Total Fiber Dietary Fiber + Functional Fiber Soluble Fibers Pectin, gum, mucilages and some hemicelluloses Insoluble Fibers Cellulose, hemicelluloses and lignin Health benefits of fibers
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Carbohydrates in Foods
Starch Fiber Nutritive Sweeteners Mono and disaccharides High fructose corn syrup Sugar alcohols
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Alternative (Non-Nutritive) Sweeteners
Yield no energy Acceptable Daily Intake (ADI) Saccharin Oldest alternative sweetener, Develops bitter taste with cooking Aspartame Cannot be used in cooking Contains phenyalanine
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Alternative Sweeteners
Neotame Similar to aspartame but not digested Acesulfamine K Can be used in cooking Sucralose Made from sucrose-can be used in cooking Tagatose Isomer of fructose, pre-biotic Stevia Recently approved by FDA for use in beverages Sold as dietary supplement
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Recommended Intake of Carbohydrates
RDA-130 grams 45%-65% of total energy needs Limit added sugars and caloric sweeteners Fiber: 14g/1000kcal is adequate intake 25g/d - women under 50 (21g/d after 51) 38g/d - men under 50 (30g/d after 51)
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Our Carbohydrate Intake
50% of total energy needs Added sugars 16% of kcal Recommendations: 6% of kcal (Dietary Guidelines) 10% of kcal (WHO) 25% of kcal (DRIs) Dietary fiber 25-50% less than recommended Average intake-1 fruit and 1 or fewer whole grain servings
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Functions of Digestible Carbohydrates in the Body
Provide energy: 4 kcal/g Spare protein Body does not utilize gluconeogenesis Prevent ketosis Incomplete breakdown of fatty acids
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Functions of Indigestible Carbohydrates in the Body
Promoting bowel health Constipation and hemorrhoids Diverticulosis and diverticulitis Reducing obesity risk Fullness and satiety Enhancing blood glucose control soluble fibers Reducing cholesterol absorption
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Carbohydrate Digestion
Mouth Salivary amylase begins digestion Small intestine Specific enzymes break down disaccharides Maltase: maltose; sucrase: sucrose; lactase:lactose Fiber not broken down
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Carbohydrate Absorption
Active absorption: Glucose and Galactose Facilitated absorption: Fructose Liver converts fructose and galactose to glucose Blood glucose used by cells Glucose storage: muscle and liver glycogen Excess glucose: converted to fat by liver (stored in adipose tissue)
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Health Concerns Related to Carbohydrate
Very High Fiber Diets (above grams) High fiber + low fluid = constipation, hemorrhoids, blockage Decrease absorption of certain minerals High Sugar Diets Increase risk of weight gain and obesity Increase risk of dental caries Cardiovascular disease?
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Health Concerns Related to Carbohydrate
Lactose Intolerance Primary Decreased lactase production Secondary Associated with disease that damage the lactase- producing cells Glucose Intolerance Hypoglycemia Hyperglycemia
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Regulation of Blood Glucose
Normal concentration: mg/dL Regulated by liver Insulin (pancreas) Hormone that facilitates transfer of glucose from blood into cells Lowers blood glucose Glucagon, Cortisol, Epinephrine, Norepinephrine and Growth Hormone Raise blood glucose
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Other Blood Sugar Disorders
Metabolic Syndrome Group of factors that increase risk for Type 2 diabetes and cardiovascular disease Hypoglycemia Reactive Hypoglycemia Exaggerated insulin response after eating Fasting Hypoglycemia Low blood sugar after fasting
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Glycemic Index and Glycemic Load
Glycemic Index (GI) Ratio of the blood glucose response to a given food, compared with a standard Influenced by many factors Based on a 50g carbohydrate serving Glycemic Load Amount of carbohydrate in consumed food multiplied by GI and divided by 100 Better reflects a food’s effect on blood glucose than GI alone
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Medical Perspective Diabetes Mellitus
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Type 1 Diabetes Mellitus
Insulin producing cells in pancreas are destroyed (autoimmune disease) Insulin therapy required for life Diet must be coordinated with insulin Exchange system, carbohydrate counting Increased risk for cardiovascular disease, blindness and kidney disease
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Type 2 Diabetes Mellitus
Progressive disease Characterized by insulin resistance Insulin production may be low, normal, or high Most common type of diabetes (90% of cases) Treatment: Diet Physical activity Medications
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