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Chapter 4 – Carbohydrates * Carbohydrates are the body’s preferred energy source Carbohydrates provide calories per gram SIMPLE CARBOHYDRATES: Monosaccharides (Single Sugars) 1. Glucose - energy source for all the body’s cells 2. Fructose - found naturally in fruit and honey 3. Galactose - part of lactose (milk sugar) Disaccharides (Sugars composed of pairs of monosaccharides) 1. Maltose - glucose + glucose 2. Sucrose - glucose + fructose 3. Lactose - glucose + galactose COMPLEX CARBOHYDATES (Polysaccharides): Glycogen An animal (human) storage form of carbohydrate. Most is stored in the , but some is also stored in the muscles and heart. Starches Composed of several glucose units linked together. Food Sources: Fiber Found naturally in plant foods, it cannot be broken down by digestion. Fibers include cellulose, hemicellulose, pectins, gums and mucilages, lignin, and resistant starches. Functions: Recommended Intake: 20-35 grams per day (upper limit is 40 grams) Food Sources: DIGESTION OF CARBOHYDRATES: Carbohydrates digest very rapidly (within 1-4 hours) Key Digestive Enzymes: Amylase – found in saliva, start digestion in the mouth Maltase – in small intestine, breaks maltose into 2 glucose units Sucrase – in small intestine, breaks sucrose into one glucose and one fructose Lactase – in small intestine, breaks lactose into one glucose and one galactose Lactose Intolerance – inability to digest lactose (milk sugar) because of a deficiency of lactase. Symptoms include bloating, gas, and diarrhea after consuming dairy products. ENERGY METABOLISM Carbohydrates → 100% → Protein → 50% → Fat → 5% → Glucose Glucose Glucose Gluconeogenesis – The making of new glucose from a non-carbohydrate source. Insulin – Hormone secreted by the for energy that allows glucose to enter the cells Glycemic Response – How quickly glucose is absorbed after a person eats, how high blood glucose rises, and how quickly it returns to normal. Glycemic Index – A method of classifying foods according to their potential for raising blood glucose. SUGAR: Functions: enhances flavor supplies texture and color to baked goods acts as a bulking agent in ice cream and baked goods provides fuel for fermentations, causing bread to rise balances the acidity of foods Health Problems Associated with Sugar: Dental Caries Nutrient Deficiencies Elevated blood glucose levels in people with diabetes Sugar does NOT cause hyperactivity or behavioral problems An average person in the U.S. consumes about 30 teaspoons of added sugar a day Common Sugary Ingredients Include: sucrose levulose corn sweeteners corn syrup dextrose high-fructose corn syrup honey molasses etc. ALTERNATIVE SWEETENERS: Currently approved by the FDA: saccharin aspartame acesulfame potassium sucralose (Splenda) neotame Sugar Replacers (Sugar Alcohols) – Type of sugar not fully absorbed by the body and has a low glycemic response. May cause gastrointestinal side effects in people sensitive to it or if too much is consumed. Common sugar alcohols include isomalt, lactitol, sorbitol, maltitol, mannitol, and zylitol. Recommended Intakes of Carbohydrates: 45-65% of total calories RDA = grams per day (average minimum amount of glucose used by the brain) To Calculate Your Carbohydrate Needs: ( ) calories needed per day (based on weight & activity) X .45 (for 45%) = calories from carbohydrates ( ) calories from carbs ÷ 4 = minimum grams per day ( ) calories needed per day (based on weight & activity) X .65 (for 65%) = calories from carbohydrates ( ) calories from carbs ÷ 4 = maximum grams per day