CHAPTER 5 CARBOHYDRATES Carbohydrates CHOs Main source of energy 4 kcals gm 45 65 AMDR Sugar starch and fiber forms Composed of carbon hydrogen oxygen Produced by plants via photosynthesis Monosaccharaides 6 carbon configuration hexose Examples glucose fructose and galactose Ribose carbon configuration pentose Examples RNA and DNA Disaccharides Chemical bonding of 2 monosaccharaides Maltose Sucrose Food source alcohol Lactose Food source sugarcane sugar beets brown white and powder sugar Food source milk and milk products People are unable to digest lactase causing intestinal gas and bloating Oligosaccharides Contain 3 to 10 single sugar units Raffinose 3 mono Stachyose 4 mono Found in Cabbage onions broccoli whole wheat legumes Can not be digested by human enzymes When we eat foods with raffinose and sachyose these oligosaccharides pass undigested into the large intestine where bacteria metabolize them Polysaccharides hundreds to thousands of glucose molecules Starch Major digestible polysaccharide Storage form of glucose for plants and animals Glycogen Storage form of glucose for humans and other animals indigestible due to beta bonds Fiber Starch 2 types of plant starch 1 Amylose Linear unbranched alpha 1 4 bonds 2 Amylopectin Highly branched alpha 1 4 and alpha 1 6 Found in starchy products and plants Examples potatoes beans bread pasta 1 4 Ratio Digestive Enzymes for Starch Amylase Secreted from mouth and pancreas Digests amylose at alpha 1 4 bonds Alpha dextrinase Secreted from intestinal enzymes Digests amylopectin at alpha 1 6 bonds What is the significance of more branches The more sites available for ezyme action causig blood glucose levels to increase more quickly Glycogen Similar to amylopectin but with more branches Allows for it to be broken down quickly by enzymes in the body cells where it is stored Liver stores 90 gm 360 kcals for energy Muscles store 300 gm 1200 kcals for use in muscle and endurance activity CHAPTER 5 CARBOHYDRATES Fiber Total fiber added to foods Occurs naturally Functional fiber insoluble fiber Soluble fiber Dissolve in water not dissolved in water Insoluble Soluble Fibers Insoluble small intestine pass into large intestine Cellulose Hemicellulose Lignin only noncarb component of dietary fiber Skin of veggies whole grains seeds of fruits Soluble Pectins Gums Mucilages Oat bran jams and jellies Health Benefits of Fiber Reduced risk of constipation and colon cancer Insoluble Decreases intestinal transit time Decreases constipation Lowers risk for diverticular disease Lowers risk of colon cancer Soluble Lowers blood cholesterol levels Delays gastric emptying Decreases blood glucose levels Carbohydrates in Foods Found in Starch Fiber Nutritive Sweeteners a Mono and disaccharides b HFCS c Sugar alcohols Alternative Non Nutritive Sweeteners Yield little energy Acceptable Daily Intake ADI guideline Saccharin Sweet N Low a Oldest alternative sweetener b ADI 5 mg kg body weight c Not for cooking bitter taste Aspartame Equal a Contains phenylalanine b ADI 50 mg kg of body weight Alternative Sweeteners Neotame a Heat stable can be used in cooking b ADI 18 mg kg body weight Acesulfamine K Sunette a Can be used in baking and cooking b ADI 15 mg kg body weight Sucralose Splenda a Can be used in cooking b Made from sucrose c ADI 5 mg kg body weight Tagatose Naturlose a Can be used in cooking b Isomer of fructose pre biotic effect in LI c ADI 0 80 mg kg body weight Stevia plus sugar alcohols Truvia and PureVia a Derived from a plant in the Amazon rainforest b ADI 4 mg kg body weight Healthy People 2020 Goals Related to CHOs Increase variety of contribution of whole grains CHAPTER 5 CARBOHYDRATES Increase variety of contribution of friuts Increase variety contribution of vegetables dark green orange legumes Reduce consumption of added sugars Recommended Intakes of CHO RDA 130 g day 45 65 of total energy needs Limit added sugars and caloric beverages a Recommendations i 6 of total energy intake Dietary Guidelines ii No more than 10 of kcals WHO iii UL of 25 of kcals DRIs Fiber 14g 1000kcal is adequate intake a 25g d for women under 50 21g d after 51 b 38 g d for men under 50 30g d after 51 Our CHO Intake 50 of total energy needs carbs Added sugars account for 16 of total kcals Dietary fiber a Triple the recommendation b High intakes related to sugar sweetened beverages which provides an additional 300 kcals day for Americans over the age of 2 a Throughout life 25 50 fiber than recommended b Avg intake 1 fruit and 1 or less whole grain servings c Does wheat four or wheat bread mean whole grains NO it must say whole wheat flour Functions of Digestible Carbohydrates 1 Provide energy Primary energy source for RBC and cells of CNS 4 kcals g glucose 2 Sparing Protein Prevent gluconeogenesis 3 Preventing ketosis incomplete breakdown of ketones Functions of Indigestible Carbohydrates 1 Promoting Bowel health Constipation and hemorrhoids Diverticulosis and diverticulitis 2 Reducing obesity risk 3 Enhancing blood glucose control 4 Reducing cholesterol absorption soluble fibers soluble fibers Carbohydrate Digestion Mouth Salivary amylase begins digestion Stomach Inactivates salivary amylase so CHO digestion stops Small Intestine Pancreatic amylase Addition of other digestive enzymes Sucrase breaks down sucrose Maltase breaks down maltose Lactase breaks down lactose Indigestible CHOs all listed above pass into the LI where they are fermented by bacteria and into acids and are secreted as fecal waste Carbohydrate Absorption Active absorption Glucose galactose Require carrier protein and ATP Facilitated absorption fructose carrier is used but not energy is required Slower absorption CHAPTER 5 CARBOHYDRATES Glucose Absorption Active Transport Following digestion glucose and galactose are pumped into absorptive cells along with sodium The ATP energy used in this process pumps sodium back out o the absorptive cell Post Absorption Liver converts fructose and galactose to Glucose has three options glucose Transported in blood for enegy in cells Stored as glycogen in muscles and liver maintains blood glucose levels Converted to fat for storage in adipose tissue Health Concerns Related to CHO Intake Very High Fiber Diets Above 50 60 gm day Combined with low fluid constipation hemorrhoids Decrease absorption of minerals High Sugar Diets Increase risk of weight gain and obestity type 2 diabetes heart disease cavities Hyperactivity Could be non nutritional as well Lactose