Carbohydrates

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

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

Carbohydrates Composed of carbon, hydrogen and oxygen Produced by plants via photosynthesis Simple carbohydrates Monosaccharides and Disaccharides Polysaccharides (more complex) Starch, Glycogen, and Fiber

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

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

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

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

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

Carbohydrates in Foods Starch Fiber Nutritive Sweeteners Mono and disaccharides High fructose corn syrup Sugar alcohols

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

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

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)

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

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

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

Carbohydrate Digestion Mouth Salivary amylase begins digestion Small intestine Specific enzymes break down disaccharides Maltase: maltose; sucrase: sucrose; lactase:lactose Fiber not broken down

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)

Health Concerns Related to Carbohydrate Very High Fiber Diets (above 50-60 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?

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

Regulation of Blood Glucose Normal concentration: 70-100mg/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

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

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

Medical Perspective Diabetes Mellitus

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

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