CHAPTER 5 -- CARBOHYDRATESCarbohydrates (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 photosynthesisMonosaccharaides • 6 carbon configuration (hexose)- Examples: glucose, fructose and galactose• Ribose carbon configuration (pentose)- Examples: RNA and DNADisaccharides• Chemical bonding of 2 monosaccharaides • Maltose- Food source: alcohol- Sucrose:- Food source: sugarcane, sugar beets, brown white and powder sugar- Lactose- Food source: milk and milk products- People are unable to digest lactase, causing intestinal gas and bloatingOligosaccharides• 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 animalsFiber- indigestible due to beta bondsStarch• 2 types of plant starch1. Amylose- Linear, unbranched, alpha 1-4 bonds2. Amylopectin- Highly branched alpha 1-4 and alpha1-6• Found in starchy products and plantsExamples: potatoes, beans, bread, pasta1:4 RatioDigestive Enzymes for Starch• AmylaseSecreted from: mouth and pancreasDigests amylose at alpha 1-4 bonds• Alpha-dextrinase- Secreted from: intestinal enzymes- Digests amylopectin at alpha 1-6 bondsWhat is the significance of more branches?- The more sites available for ezyme action,causig blood glucose levels to increase more quicklyGlycogen• 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 activityCHAPTER 5 -- CARBOHYDRATESFiber• Total fiber- Occurs naturally• Functional fiber- added to foods• insoluble fiber- not dissolved in water• Soluble fiber- Dissolve in waterInsoluble & 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 jelliesHealth Benefits of Fiber• Reduced risk of: constipation and colon cancer• InsolubleDecreases intestinal transit timeDecreases constipationLowers risk for diverticular diseaseLowers risk of colon cancer• SolubleLowers blood cholesterol levelsDelays gastric emptyingDecreases blood glucose levelsCarbohydrates in Foods• Found in:- Starch- Fiber- Nutritive Sweeteners a. Mono- and disaccharidesb. HFCSc. Sugar alcoholsAlternative (Non-Nutritive) Sweeteners• Yield little energy• Acceptable Daily Intake (ADI) guideline• Saccharin (Sweet’N Low)a. Oldest alternative sweetenerb. ADI = 5 mg/kg body weightc. Not for cooking (bitter taste)• Aspartame (Equal)a. Contains phenylalanine b. ADI = 50 mg/kg of body weight Alternative Sweeteners• Neotamea. Heat-stable, can be used in cookingb. ADI = 18 mg/kg body weight• Acesulfamine K (Sunette)a. Can be used in baking and cookingb. ADI = 15 mg/kg body weight• Sucralose (Splenda)a. Can be used in cookingb. Made from sucrosec. ADI = 5 mg/kg body weight• Tagatose (Naturlose)a. Can be used in cookingb. Isomer of fructose, pre-biotic effect in LIc. ADI = 0-80 mg/kg body weight• Stevia (plus sugar alcohols = Truvia and PureVia)a. Derived from a plant in the Amazon rainforestb. ADI = 4 mg/kg body weight Healthy People 2020 Goals Related to CHOs• Increase variety of contribution of wholegrainsCHAPTER 5 -- CARBOHYDRATES• Increase variety of contribution of friuts• Increase variety & contribution of vegetables (dark green, orange, legumes) • Reduce consumption of added sugarsRecommended Intakes of CHO• RDA: 130 g/day• 45-65% of total energy needs• Limit added sugars and caloric beveragesa. 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 intakea. 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 kcalsa. Triple the recommendationb. High-intakes related to sugar sweetened beverages, which provides an additional 300 kcals/day for Americans overthe age of 2.• Dietary fibera. Throughout life, 25-50% fiber than recommendedb. Avg intake: 1 fruit and 1 or less whole grain servingsc. Does ‘wheat four’ or ‘wheat bread’ mean ‘whole grains’? NO! it must say whole wheat flourFunctions of Digestible Carbohydrates 1. Provide energy- Primary energy source for RBC and cells of CNS- 4 kcals/g (glucose)2. Sparing Protein - Prevent gluconeogenesis3. Preventing ketosis- incomplete breakdown of ketonesFunctions of Indigestible Carbohydrates 1. Promoting Bowel health- Constipation and hemorrhoids- Diverticulosis and diverticulitis2. Reducing obesity risk3. Enhancing blood glucose control- soluble fibers4. Reducing cholesterol absorption- soluble fibersCarbohydrate 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 wasteCarbohydrate Absorption• Active absorption: Glucose/ galactose- Require carrier protein and ATP• Facilitated absorption: fructose- carrier is used but not energy is required- Slower absorptionCHAPTER 5 -- CARBOHYDRATESGlucose 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 toglucose• Glucose has three options: - Transported in blood for enegy in cells- Stored as glycogen in muscles and liver