Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.1 Chapter 2 Carbohydrates Man shall not live by bread alone.

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.2 Key Concepts Carbohydrate foods provide practical energy (calorie) sources because of their availability, relatively low cost, and storage capability. Carbohydrate structures vary from simple to complex to provide both quick and extended energy for the body.

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.3 Classes of Carbohydrates Monosaccharides –Simple sugar –Simple carbohydrate Glucose Fructose Galactose

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.4 Classes of Carbohydrates, cont’d Disaccharides –Double sugar –Simple carbohydrate Sucrose (glucose and fructose) Lactose (glucose and galactose) Maltose (glucose and glucose)

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.5 Classes of Carbohydrates, cont’d Polysaccharides –Starch –Glycogen –Dietary fiber

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.6 Starch Most significant polysaccharide in the diet Whole grains retain the bran layer, inner germ, and endosperm, including the nutrients naturally found in the plant Enriched grains are refined grains that have nutrients added back to them

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.7 Other Sweeteners Nutritive sweeteners –Sugar alcohols (sorbitol, mannitol, xylitol) Non-nutritive sweeteners –Artificial sweeteners in food (Examples in next slide)

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.8 Sweetness of Sugars and Artificial Sweeteners

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.9 Focus on Dietary Fiber Cellulose –Remains undigested in the gastrointestinal tract and provides bulk to a diet –Bulk helps move the food mass through the intestine (prevents constipaton) –Examples: Stems, leaves of vegetables, corn hull, beans, coverings of seeds and grains

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.10 Focus on Dietary Fiber, cont’d Noncellulose polysaccharides –Absorb water and swell to a larger bulk –Examples: pectins from fruit; gums & mucilages – secretions from plants like okra; algal substances - seaweed Lignin –Only noncarbohydrate type of dietary fiber –Woody parts of plants (broccoli stems & seeds)

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.11 Focus on Dietary Fiber, cont’d Divided into two groups based on solubility –Insoluble –Soluble Many health organizations recommend increasing intake of dietary fiber **38 g/day for men **25 g/day for women

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.12 Focus on Dietary Fiber, cont’d Sudden increases in fiber can result in gas, bloating, and constipation Excessive amounts of dietary fiber can trap small amounts of minerals and prevent their absorption into the gastrointestinal tract

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.13 Summary of Dietary Fiber Classes

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.14 Energy Function of Carbohydrates Basic fuel supply –Energy for physical activities and all work of body cells Reserve fuel supply –Provided by stored glycogen –Available to maintain a normal blood glucose level

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.15 Special Tissue Functions of Carbohydrates Liver –Stored glycogen protect cells from depressed metabolic function Protein and fat –Carbohydrates regulate proteins and fat used for energy Heart –Glycogen is vital emergency back up fuel for heart muscle

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.16 Digestible Food Sources of Carbohydrates Central nervous system –Brain dependent on minute-to-minute supply of glucose Starches –Provide fundamental complex carbohydrates Sugars –Readily absorbed –High-sugar diets carry health risks

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.17 Teaspoons of High-Fructose Corn Syrup Consumed We eat too much sugar!

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.18 Digestion of Carbohydrates Mouth –Mechanical or muscle functions break food mass into smaller particles –Chemical digestion begins with salivary amylase Stomach –Peristalsis continues mechanical digestive process

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.19 Digestion of Carbohydrates, cont’d Small intestine –Peristalsis continues mechanical digestion –Pancreatic secretions - Pancreatic amylase breaks starches down into disaccharides and monosaccharides –Intestinal secretions - Sucrase, lactase, and maltase help break down their starches

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.20 Body Needs for Carbohydrates 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

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.21 Summary Carbohydrates are the primary source of energy for most of the world’s population. Carbohydrates are distributed as the plant sources: grains, legumes, vegetables, and fruits. The two basic types of carbohydrates are simple and complex. Simple carbohydrates are composed of single- and double-sugar units (monosaccharides and disaccharides)

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.22 Summary, cont’d Complex carbohydrates are composed of many sugar units. Dietary fiber is a complex carbohydrate that is not digestible and is found mainly in the structural parts of plants. Carbohydrate digestion begins in the mouth, continues in the stomach, moves to the small intestine, and finally arrives in the large intestine and exits through the anus.

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.23 FATS -Key Concepts Dietary fat supplies essential body tissue needs, both as an energy fuel and a structural material. Foods from animal and plant sources supply distinct forms of fat that affect health in different ways. Excess dietary fat, especially from animal food sources, is a negative risk factor in overall health.

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.24 The Nature of Fats Dietary importance –Concentrated fuel for energy Classes of fats –Lipids –Glycerides Triglycerides –Fatty acids –Lipoproteins

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.25 Fatty Acids ESSENTIAL fatty acids means that it is ESSENTIAL that we eat them Saturated fatty acids –Filled or “saturated” with hydrogen Unsaturated fatty acids –Omega 3 and omega 6 –Not completely filled with hydrogen –Less heavy, less dense –Monounsaturated: one unfilled spot –Polyunsaturated: two or more unfilled spots

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.26 Phospholipids Triglyceride derivative: third fatty acid replaced by phosphate group Partially hydrophobic, partially hydrophilic – remember cell wall? Allow transport of fats through bloodstream

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.27 Cholesterol Not a fat A fat-related compound –Only from animal foods Egg yolks Liver, kidney Meats –Synthesized in the liver –Diet should be low in cholesterol –Linked with heart disease

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.28 Functions of Fat in Foods Fat in foods provide: –Energy –Essential nutrients –Flavor and satisfaction –Fat substitutes are not absorbed and therefore do not provide energy or essential nutrients but may provide flavor and satisfaction

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.29 Functions of Fat in the Body Adipose tissue –Protects organs –Helps regulate temperature Cell membrane structure –Forms part of cell membrane –Helps transport nutrients across cell membranes Second choice to achieve energy

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.30 Food Sources of Fat Animal fats Plant fats Hydrogenated fats (trans fats) –Commercial fat products raise health concerns –Food industry now offers trans-free products

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.31 A QUESTION FOR YOU! Why are trans fats “worse” than saturated fats? Studies show they lower HDL cholesterol and raise LDL cholesterol, whereas saturated fats only raise LDL cholesterol, leaving HDL the same or better

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.32 FDA Health Claims Claims that link one or more dietary components to the reduced risk of a specific disease need to be approved by the FDA –Fat and cancer –Saturated fat and cholesterol and heart disease

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.33 Key Concepts Dietary fat supplies essential body tissue needs, both as an energy fuel and a structural material. Excess dietary fat, especially from animal food sources, is a negative risk factor in overall health.

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.34 Dietary Fat and Health The American diet is high in fat. Excess calories are stored as fat. Animal food sources contribute to excess cholesterol and saturated fat in the diet. A decrease in saturated fat reduces serum total cholesterol. Monounsaturated fats reduce LDL cholesterol when substituted for saturated fat.

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.35 Digestion of Fats Mouth - mechanical Stomach - mechanical Small intestine – chemical & mechanical –Bile from the gallbladder –Enzymes from the pancreas –Enzymes from the small intestine –Absorption

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.36 Dietary Fat Requirements Healthy diet guidelines: –Stress the health benefits of a diet low in fat overall, but more so with saturated fat, and cholesterol –Recommend that the fat content should not exceed 20% to 35% of total kilocalories Less than 10% of kilocalories should be from saturated fat Dietary cholesterol should be limited to 300 mg/day

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.37 Mosby items and derived items © 2006 by Mosby, Inc. Slide 37 Dietary Guidelines for Americans Control saturated fat and cholesterol Use only lean cuts of all meats; use more poultry and seafood (shellfish are low in fat but high in cholesterol) Limit eggs to two or three per week –Can discard the yolk to decrease fat Use low-fat or fat-free milk and milk products Avoid adding too much fat in food preparation – food should not slide across the plate!

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.38 Summary Classes of fat include lipids, triglycerides, fatty acids, and lipoproteins Fatty acids can be saturated or unsaturated Essential fatty acids are necessary to aid in tissue strength, muscle tone, cholesterol metabolism, blood clotting, and heart action

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.39 Summary, cont’d Cholesterol is a sterol only found in animal foods that is vital in human metabolism Digestion of fat includes digestive agents such as bile and pancreatic lipase Fatty acids and glycerides are incorporated into chylomicrons and absorbed via the lymphatic system into the bloodstream