Transcript 2 - Quia
Williams' Basic Nutrition & Diet Therapy 14th Edition Chapter 2 Carbohydrates Copyright © 2013 Mosby, Inc., an imprint of Elsevier Inc. All rights reserved. 1 Carbohydrates: Energy Source, Their Structures, Role as Fiber 1. Carbohydrate foods provide practical energy sources because of their availability, relatively low cost, and storage capability. 2. Carbohydrate structures vary from simple to complex, providing both quick and extended energy for the body. 3. Dietary fiber, an indigestible carbohydrate, serves separately as a regulatory agent within the gastrointestinal tract. Copyright © 2013 Mosby, Inc., an imprint of Elsevier Inc. All rights reserved. 2 Nature of Carbohydrates (p. 13) Relation to energy ◦ Basic fuel source The human body can rapidly break down carbohydrates and they provide the major source of energy that is measured in calories** Copyright © 2013 Mosby, Inc., an imprint of Elsevier Inc. All rights reserved. 3 Classes of CHO’s A CHO is composed of C, H, O Monosaccharides and disaccharides are small, simple structures of only one and two sugar units and are referred to as simple CHO’s Copyright © 2013, 2009, 2005 Mosby, Inc., an imprint of Elsevier Inc. All rights reserved. Classes of Carbohydrates (p. 14) Monosaccharides ◦ Energy demands will determine if the monosaccharides are then used for immediate energy or stored as glycogen for later use ◦ Glucose: basic single sugar in human metabolism Circulates in the blood AKA dextrose* ◦ Fructose: primarily found in fruits and honey* ◦ Galactose: product of lactose digestion Copyright © 2013 Mosby, Inc., an imprint of Elsevier Inc. All rights reserved. 5 Classes of Carbohydrates (cont’d) (p. 15) Disaccharides ◦ Sucrose: common table sugar ◦ Lactose: sugar found in milk* *glucose and galactose ◦ Maltose: product of intermediate breakdown of starch by the body Copyright © 2013 Mosby, Inc., an imprint of Elsevier Inc. All rights reserved. 6 Classes of Carbohydrates Polysaccharides ◦ Complex carbohydrates ◦ Composed of many single-sugar units Starch: most significant polysaccharides Includes cereal, pasta, crackers, bread and other baked goods; legumes in the form of beans and peas, potatoes, rice, corn and bulgur, other vegetables of the root variety* Glycogen: formed within body tissues; crucial to metabolism and energy balance Found in liver and muscles, where it is constantly recycled Copyright © 2013 Mosby, Inc., an imprint of Elsevier Inc. All rights reserved. 7 Dietary Fiber (p. 17) Divided into two groups based on solubility: soluble and insoluble. Cellulose, lignin, and most hemicelluloses are not soluble in water Whole grains Legumes Vegetables Fruits with as much skin remaining as possible Table 2-2* Copyright © 2013 Mosby, Inc., an imprint of Elsevier Inc. All rights reserved. 8 Dietary Fiber (cont’d) (p. 17) Health organizations emphasize role of dietary fiber Recommended daily intake for men age 50 and younger: 38 g/day For women: 25 g/day* Increases should be gradual The average American does not consume the recommended servings of whole grains, vegetables and fruit on a daily basis* Copyright © 2013 Mosby, Inc., an imprint of Elsevier Inc. All rights reserved. 9 Cellulose (p. 17) Cellulose: chief component of cell walls in plants Lignin ◦ Only noncarbohydrate dietary fiber ◦ Large compound, forms woody part of some plants Noncellulose polysaccharides ◦ Absorb water and swell to larger size, slowing stomach emptying ◦ Bind with bile acids ◦ Provide bulk for normal muscle action Copyright © 2013 Mosby, Inc., an imprint of Elsevier Inc. All rights reserved. 10 Other Sweeteners (p. 20) Nutritive sweeteners ◦ Sugar alcohols (sorbitol, mannitol, xylitol) Result in slowed digestion/osmotic diarrhea* Nonnutritive sweeteners ◦ Artificial sweeteners in food Does not provide any kcal and present with a sweet taste without contributing to an individuals total energy intake* Copyright © 2013 Mosby, Inc., an imprint of Elsevier Inc. All rights reserved. 11 Functions of Carbohydrates (p. 21) Primary energy function ◦ Basic fuel supply Burn in the body at the rate of 4kcal/g* Physical activities Work of body cells ◦ Reserve fuel supply Liver stores about 100 g of glycogen Muscle stores 300-400 g Maintains blood glucose level Copyright © 2013 Mosby, Inc., an imprint of Elsevier Inc. All rights reserved. 12 Other Sweeteners (cont’d) (p. 22) Copyright © 2013 Mosby, Inc., an imprint of Elsevier Inc. All rights reserved. 13 Functions of Carbohydrates (cont’d) (p. 21) Primary energy function (cont’d) ◦ Special tissue functions Liver: Glycogen reserves maintain overall energy balance Carbohydrate protects protein and fat supply Central nervous system depends on constant carbohydrate supply Copyright © 2013 Mosby, Inc., an imprint of Elsevier Inc. All rights reserved. 14 Food Sources of Carbohydrates (p. 22) Starches ◦ Most important carbohydrate in the diet* ◦ Whole-grain starches such as rice, wheat, corn, potatoes* Sugars ◦ Not necessarily bad ◦ Added sugars provide empty calories ◦ Moderation is key TABLE-2-5 Dairy products* Copyright © 2013 Mosby, Inc., an imprint of Elsevier Inc. All rights reserved. 15 Digestion of Carbohydrates (p. 24) Mouth ◦ Digestion of CHO foods, starches, and sugars begin in the mouth* ◦ Mechanical or muscle functions break food mass into smaller particles ◦ Chemical process in which enzymes begin breaking food down Stomach ◦ Peristalsis continues mechanical breakdown* ◦ Gastric secretions continue chemical breakdown of nutrients ◦ Secretions do not break down carbohydrates but stop Copyright © 2013 Mosby, Inc., an imprint action of salivary amylase of Elsevier Inc. All rights reserved. 16 Glycemic Index GI ranks foods according to how fast blood glucose levels rise after consuming a specific amount (50g) as compared with a reference food such as white bread or pure glucose* Copyright © 2013, 2009, 2005 Mosby, Inc., an imprint of Elsevier Inc. All rights reserved. Digestion of Carbohydrates (cont’d) (p. 25) Small intestine ◦ Peristalsis continues mechanical breakdown of food ◦ Enzymes from pancreas and intestine continue chemical breakdown Copyright © 2013 Mosby, Inc., an imprint of Elsevier Inc. All rights reserved. 18 Digestion of Carbohydrates (cont’d) (p. 26) Pancreatic secretions ◦ Enter duodenum through common bile duct ◦ Contain pancreatic amylase to continue breakdown of starch Intestinal secretions ◦ Three disaccharidases: sucrose, lactase, maltase ◦ Render disaccharides into monosaccharides Copyright © 2013 Mosby, Inc., an imprint of Elsevier Inc. All rights reserved. 19 Recommendations for Dietary Carbohydrate (p. 26) Dietary Reference Intakes ◦ 45% to 65% of adult’s total caloric intake should come from carbohydrate foods ◦ Limit sugar to no more than 25% of calories consumed Dietary Guidelines for Americans, 2010 ◦ Does not provide a specific caloric number or percentage, but does provide recommendations Copyright © 2013 Mosby, Inc., an imprint of Elsevier Inc. All rights reserved. 20 Cultural Considerations (p26) Lactose intolerant individuals can usually tolerate low lactose milk products such as cheese* Copyright © 2013, 2009, 2005 Mosby, Inc., an imprint of Elsevier Inc. All rights reserved.