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Chapter 9 Nutrition.

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1 Chapter 9 Nutrition

2 Learning Objectives Explain the role of the gastrointestinal system in the digestion of food. Describe how food is digested and absorbed. List the functions of each of the six classes of essential nutrients. Define macronutrient and micronutrient. Identify the food sources of proteins, carbohydrates, and fats. Identify the food sources of dietary fiber. List the possible health benefits of dietary fiber. Identify the food sources of each of the vitamins and minerals. Describe the changes in nutrient needs as an individual ages. Differentiate between anorexia nervosa, bulimia, and binge eating disorder. Discuss the different types of nutritional support. Identify guidelines for the nutritional assessment.

3 Anatomy and Physiology of the Gastrointestinal System

4 Gastrointestinal System (GI tract or “gut”)
The long, continuous tube that receives and transports food, absorbs nutrients, and eliminates waste products of digestion Primary organs Mouth, pharynx, esophagus, stomach, small intestine, and large intestine Accessory organs Liver, gallbladder, and pancreas Roles in food digestion even though not part of digestive tract

5 Digestion and Absorption
92% to 97% of diet digested and absorbed Water, simple sugars, vitamins, minerals, and alcohol absorbed in their original form Lipids, proteins, and complex sugars must be converted to simple forms before they are absorbed

6 Digestion and Absorption
Hydrolysis Water splits complex molecules into smaller units Enzymes Govern the process of hydrolysis, along with bile and hydrochloric acid Help break down food particles to their simplest form so nutrients can be absorbed Found throughout intestinal tract, except in the large intestine Only water, salt, vitamins, and minerals are absorbed in the colon

7 Regulators of the Gastrointestinal Tract
Neural control Managed by autonomic nervous system and nerve network in gut wall called the enteric nervous system Autonomic system: sympathetic and parasympathetic nerves Parasympathetic nerves stimulate digestive activity Sympathetic nerves inhibit activity Parasympathetic effect conveyed by vagus nerve: acid stimulation in stomach in response to sight/smell of food Enteric nervous system receives information from receptors in gastric mucosa that are sensitive to acidity of the gastrointestinal tract and the feeling of fullness

8 Regulators of the Gastrointestinal Tract
Hormone secretion Secreted into the gastrointestinal tract to help regulate gastric pH, gastric motility, and appetite Stimulate the pancreas to secrete insulin and enzymes

9 Digestive Process: Mouth
Teeth grind and crush food into small particles Food forms mass moistened and lubricated by saliva A secretion containing an enzyme known as amylase (ptyalin) digests any present starch Mass, or bolus, then passed to the pharynx and through the esophagus by the process of swallowing Peristalsis moves the food rapidly through the esophagus into the stomach What are the three areas of the gastrointestinal system in which digestion of food occurs?

10 Digestive Process: Stomach
The mass is mixed with gastric secretions Active chemical digestion is accomplished by the secretion of gastric juice Produces average of 2000 to 2500 ml gastric juice daily The juice contains hydrochloric acid, enzymes, mucus, and the GI hormone gastrin Aids in digestion by converting the mass to a semiliquid substance called chyme

11 Digestive Process: Stomach
Normally emptied in 1 to 4 hours Carbohydrates leave the stomach most rapidly, followed by protein, and then fat Valves (sphincters) at entrance (cardiac sphincter) and exit (pyloric sphincter) of the stomach prevent backflow of food from stomach into pharynx and from duodenum into the stomach What happens to the emptying of the stomach when a mixed diet has been consumed?

12 Digestive Process: Small Intestine
Divided into the duodenum, the jejunum, and the ileum Most digestion completed in duodenum; jejunum and ileum function mostly in the absorption of nutrients The remaining chyme is delivered to the large intestine

13 Digestive Process: Large Intestine
Water and electrolytes are absorbed, leaving a mass of wastes called feces Fecal mass is stored in the rectum, where it triggers the defecation reflex When anal sphincters relax, feces pass out of the body through the anus

14 Mechanisms of Absorption
Absorption is accomplished by the combination of the processes of diffusion and active transport Diffusion Movement of particles from an area of higher concentration to an area of lower concentration Active transport Requires the input of energy for the movement of particles across a membrane against an energy gradient Requires a carrier protein Best-known carrier is the intrinsic factor, which is responsible for the absorption of vitamin B12

15 Mechanisms of Absorption
Small intestine Primary organ of absorption 22 feet long and arranged in folds Surface of folds covered with fingerlike projections called villi Absorb nutrients into the blood and lymph vessels that support them Absorbs several hundred grams of carbohydrate, g or more of fat, 50 to 100 g amino acids, 50 to 100 g of ions, and 7 to 8 L of water each day

16 Nutrients: Carbohydrates
Digestion begins in the mouth, where the enzyme amylase is released In the stomach, amylase activity halted when it comes into contact with hydrochloric acid If carbohydrates remain in the stomach long enough, hydrochloric acid reduces most to their simplest form Stomach generally empties into the small intestine before this occurs, so most of the digestion of carbohydrates occurs within the small intestine Macronutrients are essential nutrients that have a large minimum daily requirement. What are the names of some macronutrients? Other dietary essentials, including vitamins and minerals, are called micronutrients because they are required in small quantities.

17 Nutrients: Carbohydrates
In the small intestine, pancreatic amylase is released to continue carbohydrate digestion Pass through the villi into the bloodstream, where carbohydrates carried by the portal vein to the liver From the liver, most of the glucose is transported to the tissues Some stored for later use in the liver in the form of glycogen and in the muscle Some forms, particularly fiber, cannot be digested by humans and are excreted unchanged in the feces

18 Nutrients: Protein Digestion does not begin until it reaches the stomach Split into smaller molecules Most digestion occurs in the duodenum Almost all of the protein is absorbed by the time it reaches the end of the jejunum Only 1% of ingested protein found in the feces

19 Nutrients: Fat Digestion begins in the stomach Gastric lipase
An enzyme, breaks down the triglycerides that make up fat into fatty acids and glycerol Major portion of fat digestion takes place in the small intestine Peristaltic action of small intestine, along with bile secreted by the liver, breaks down the larger fat globules into smaller particles

20 Nutrients: Fluids, Vitamins, and Minerals
Absorbed through the intestinal mucosa Each day about 8 L of fluid from the body pass back and forth across gut membrane to keep the nutrients in solution Vitamins and water pass unchanged from the small intestine into the blood by passive diffusion Mineral absorption is a more active, complex process that takes place in several stages

21 Factors Affecting Digestion
Psychological state Look, smell, and taste of food have effect on digestion Emotions such as fear, anger, and worry can inhibit peristalsis and depress gastric secretions Bacterial action Needed to help form vitamin K, vitamin B12, thiamine, and riboflavin Produce various gases, acids, and other toxic substances Food processing What may cause secretions of saliva and gastric juices to increase? The gut is inhabited by about 100 different species of bacteria. A healthy person is not usually disturbed by these bacteria because they dwell in the gastrointestinal tract as normal flora. Bacterial action is most intense in the large intestine. The manner in which the food is cooked can affect digestion. What else may affect digestion other than the manner in which food is cooked? Cooked foods generally more digestible than raw foods

22 Energy Expenditure Measurement of energy expenditure
Basal metabolic rate (BMR) Factors that can cause the metabolic rate to vary Body size and composition Periods of growth Secretion of hormones Temperature Menstrual cycle Pregnancy In the context of nutrition, energy refers to the way in which the body makes use of the energy received through the food that is eaten. What are the three components of energy expenditure?

23 Energy Expenditure Energy measurements and calculations Calorie
Standard unit for measuring energy Amount of heat energy needed to increase temperature of 1 g of water at standard temperature by 1° C Measure of human energy expenditure Direct calorimetry Indirect calorimetry Doubly labeled water What can the measure of human energy expenditure be used to calculate? Because actual measures require expensive procedures, many equations have been developed to estimate measurements of energy expenditure and requirements based on patient characteristics.

24 Carbohydrates Organic compounds consisting of carbon, hydrogen, and oxygen All the sugars and starches that people eat and most types of fibers Plants manufacture and store carbohydrates as their chief source of energy Glucose main sugar in the blood and body’s basic fuel; serves as primary source of energy Most of the energy we require is consumed in the form of carbohydrates. What are the simplest sugars?

25 Carbohydrates Classified according to the number of simple sugars or saccharides Monosaccharides 1 saccharide Disaccharides 2 saccharides Oligosaccharides 3 to 10 monosaccharides Polysaccharides 10 to 10,000 or more molecules What are some examples of each classification of sugar? Food sources?

26 Carbohydrates Metabolism
Converted to glucose for immediate use by the body’s cells and to glycogen for storage Serum glucose level maintained at normal through the regular intake of nutrients, storage or breakdown of glycogen, glucogenesis, and gluconeogenesis Normal blood glucose levels: 70 to 100 mg/100 ml under fasting conditions After a meal, blood glucose level may rise to 130 mg/100 ml but returns to normal within 2 to 3 hours During long periods of fasting or prolonged exercise, glycogenolysis may not be able to provide sufficient glucose. Then amino acids are converted to glucose in the liver through the process of gluconeogenesis. What hormones are involved in the regulation of blood glucose levels?

27 Carbohydrates Dietary fiber
A group of polysaccharides that act differently from other carbohydrates Found only in plant foods and are resistant to human digestive enzymes Major digestive role is to help form a soft, firm stool and to aid in the process of elimination Types Insoluble Soluble What fibers are insoluble? Insoluble fibers act as sponges to absorb many times their weight in water, swelling up in the intestine. Insoluble fibers help provide a full feeling long after they have been consumed and seem to help normalize intestinal transit time. What fibers are soluble? Soluble fiber prevents or reduces the absorption of certain substances in the bloodstream.

28 Carbohydrates Functions of carbohydrates Recommended Dietary Allowance
Major source of energy to body tissues Sole source of energy for the brain Maintain functional integrity of nerve tissue Spare fats from being used for metabolism Precursors (basic building blocks) for other physiologic substances Recommended Dietary Allowance Carbohydrates should comprise 45% to 65% What sugar remains in the intestine the longest? Glucuronic acid is a product of glucose metabolism that combines with toxins in the liver and converts them to a form that is readily excreted.

29 Lipids Include fats, oils, waxes, and related compounds
May be solid or liquid forms Insoluble in water Contain carbon, hydrogen, and oxygen Triglycerides: most common fat found in foods of both animal and plant origin Fat metabolism uses more oxygen and releases more energy than either carbohydrate or protein metabolism. Triglycerides consist of how many fatty acids?

30 Lipids Saturated fatty acids Unsaturated fatty acids
Loaded with all the hydrogen atoms they can carry Solid at room temperature Unsaturated fatty acids Do not have all the hydrogen atoms they can carry Liquid at room temperature Fats that are largely saturated come chiefly from animal sources. What are some examples of saturated fats? The important dietary unsaturated fats come from plants and fish.

31 Lipid Transport and Storage
Most are absorbed into the lymphatic system through the intestinal mucosa The exception is certain fatty acids that are absorbed directly into the portal blood For fat to be digested, it must be emulsified, or pulled into suspension with digestive juices Bile (secretion of liver) needed to emulsify fat

32 Lipid Transport and Storage
Once emulsified, fats can be broken down and absorbed Lipoproteins Protein that transports lipids in the bloodstream Chylomicrons, high-density lipoproteins (HDLs), low-density lipoproteins (LDLs), and very-low-density lipoproteins (VLDLs) Cholesterol found in the LDLs increases the risk of atherosclerosis by contributing to plaque buildup on the artery walls. HDLs carry cholesterol from the bloodstream to the liver to be degraded and excreted. What is the difference between white fat and brown fat?

33 Lipid Metabolism A source of energy for most body tissues except the brain, blood cells, skin, and renal medulla Lipolysis Fat cells release glycerol and free fatty acids Liver converts it to triglycerides or glucose Free fatty acids bind to albumin for transportation in the blood and interstitial tissue Most lipids carried to liver for conversion to energy or for the synthesis of new triglycerides The center for lipid metabolism is the liver, which helps to regulate lipid levels in the body by the following processes: Synthesis of triglycerides and other lipids from fatty acids, carbohydrates, or protein Desaturation of fatty acids Catabolism (breakdown) of triglycerides for use as energy How does ketoacidosis occur?

34 Recommended Dietary Allowance
20% to 35% of the adult diet should be composed of fats Unsaturated fats rather than saturated fats minimize the risk of heart disease Studies have shown that Americans tend to consume too much fat. How can consuming too much fat affect the body?

35 Food Sources of Fat Saturated fats Unsaturated fats
Animal products: beef, dairy products, and eggs Unsaturated fats Vegetable oils, including corn oil, cottonseed oil, and safflower oil Cattle and pigs are being bred to yield beef and pork that is lower in saturated fat.

36 Lipid Function Store energy Maintain healthy skin and hair
Carry fat-soluble vitamins Supply essential fatty acids Promote satiety Carbohydrates are the body’s main source of food energy, but fats are the most concentrated source. How many kilocalories per gram do fats supply?

37 Proteins Basic structure of a chain of amino acids that can form many different configurations and combine with other substances Contains carbon, hydrogen, oxygen, nitrogen, sulfur: sometimes metals, acids, lipids, polysaccharides Simple proteins Made of only amino acids Conjugated proteins Made of amino acids in combination with other substances

38 Proteins Amino acids Nine essential: must be obtained from the diet
Body can manufacture enough of the other amino acids from the essential amino acids Complete protein Contains all 9 essential amino acids in sufficient quantity and ratio for the body’s needs Incomplete proteins Lack one or more of the essential amino acids There are 22 common amino acids, and they can be bonded in a variety of ways to form different proteins. The body uses all 22 amino acids, but only nine of them are considered essential amino acids. What are the nine essential amino acids? Complete proteins are generally of animal origin and are found in foods such as meat, poultry, fish, milk, cheese, and eggs. Incomplete proteins are of plant origin, such as the proteins in grains, legumes, nuts, and seeds.

39 Protein Metabolism and Synthesis
Deamination Protein is broken down in the small intestine to the constituent amino acids Protein synthesis Controlled by DNA in the cells DNA: provides the form to link up the exact combination of amino acids needed to form a particular protein What does deamination produce? If one or more of the essential amino acids are in short supply or are not available at all, nonessential amino acids cannot be used to form a protein.

40 Protein Deficiency The body cannot store protein, so it needs to be eaten each day If protein intake is inadequate, nitrogen will be conserved by the kidneys, causing the urine nitrogen to be low Nitrogen in the urine is a good indicator of protein levels in the body. What are the signs and symptoms of protein deficiency?

41 Evaluation of Protein Quality
Should include both the quantity and the quality of the protein consumed Eating a mixture of foods in a meal, if the quantity is sufficient, tends to provide all of the essential amino acids The average American consumes considerably more than the RDA for protein. The protein content, by weight, of cooked meat, fish, poultry, and milk solids is between 15% and 40%. The protein content of cooked cereals, beans, and lentils ranges from 3% to 10%.

42 Functions of Proteins Furnish building blocks (amino acids) to build and repair tissue Serve as an energy source Help form enzymes, hormones, and other body fluids and secretions Assist in the transport of fats, fat-soluble vitamins, and other substances Help maintain osmolarity of body fluids

43 Recommended Dietary Allowance
Should contribute 10% to 35% of the macronutrients in the adult diet The recommended dietary reference intake for protein is 56 g/day for males and 46 g/day for females.

44 Vitamins Fat soluble Water soluble Vitamins A, D, E, and K
Usually absorbed in the body with other lipids Water soluble B-complex group (thiamine, riboflavin, niacin, B6, folate, B12, pantothenic acid, and biotin) and vitamin C (ascorbic acid) Readily excreted from the body Vitamins are organic compounds that the body needs for normal growth and development. Can the body manufacture vitamins? Vitamins are usually designated by letters and are classified into two groups on the basis of solubility: (1) fat-soluble vitamins, which can be dissolved in fat; and (2) water-soluble vitamins, which can be dissolved in water.

45 Minerals Enzyme regulation, maintain acid-base balance and osmotic pressure, and maintain nerve and muscular irritability Macrominerals Calcium, phosphorus, magnesium, sulfur, sodium, chloride, potassium Microminerals or trace elements Iron, zinc, iodine

46 Minerals Ultratrace elements Ionized forms
Selenium, chromium, copper, manganese, molybdenum, boron, cobalt Ionized forms Sodium, potassium Constituents of organic compounds Phospholipids, hemoglobin Minerals are involved in enzyme regulation, maintenance of acid-base balance and osmotic pressure, and maintenance of nerve and muscular irritability. What are the macrominerals and the microminerals? Minerals account for 4% to 5% of body weight.

47 Water Largest component of the body and tissues; essential to all body life processes Intake of water is controlled by thirst Also ingested through food The body cannot store water Essential that all living things replenish water daily to maintain health and efficiency What are some of the functions of water in the body? Water is lost from the body through the kidneys as urine, through the intestines as part of feces, through the lungs with expired air, and through the skin as evaporated sweat. The amount of water taken in daily should be equivalent to the amount of water lost.

48 Water The longest that people can live without water is approximately 4 days Adults generally should take in about 2500 ml, or 2 to 3 quarts, per day

49 Age-Related Changes Energy
Normal decline in metabolism and common decrease in physical activity, lower energy needs with age Often reduce the kilocalories taken in per day Can result in inadequate intake of essential nutrients Psychosocial factors also may lead to poor nutrition in the older person Depression, cognitive impairment, and loneliness The recommended daily energy intake for light to moderately active older adults is 30 kcal/kg of body weight. What does the term “failure to thrive” mean?

50 Nutritional Care of the Older Adult
Dietary planning Meals need to be appealing, taking into consideration individual likes and dislikes, and should be tasteful and filling Nutrition programs Community-based programs, administered by public and private agencies, provide hot, nutritious meals to older adults Problems such as difficulty swallowing, dentures that do not fit properly, and arthritis, which makes using utensils uncomfortable, must be considered. What type of special dietary needs may the older adult have?

51 Nutritional Care of the Older Adult
Nutritional needs during prolonged illness Increased nutritional needs during illness Nasogastric tube feedings or parenteral nutrition may be required Nutritional care in institutional settings Periodic reassessment of nutritional status is critical What problems are older adults at risk for having? Good nutrition can have a dramatic effect on the physical, mental, and emotional function of your older patients. Age-related changes, chronic and acute conditions, cognitive and emotional disorders, medications, and situational factors can contribute to inadequate nutritional intake, digestion, or elimination.

52 MyPyramid Based on recommendations from the 2005 USDA Dietary Guidelines for Americans Includes figure climbing the steps of the pyramid to emphasize exercise in addition to nutrition Colored bands on the pyramid represent the recommended proportions of vegetables (green), grains (orange), fruits (red), milk products (blue), meats and beans (purple), and oils (yellow) Personalized pyramid Enter age, gender, and activity level

53 Figure 9-1A

54 Food Labeling People have expressed an increased need to be informed about what they are eating Many more foods are now labeled so that the average person can make determinations about the quality and quantity of the nutrients consumed

55 National Guidelines for Diet Planning
Many guidelines are available on proper nutrition to maintain health and prevent disease Surgeon General’s Report on Nutrition and Health can be used as a basis for dietary planning (Table 9-14)

56 Figure 9-2

57 Vegetarian Diets Many vegetarians eat all foods except red meat, although some exclude poultry and fish as well Lactovegetarian diet Includes milk, cheese, and other dairy products but excludes meat, fish, poultry, and eggs Lacto-ovo-vegetarian diet Includes dairy products and eggs but excludes meat, fish, and poultry Vegan Consumes no foods of animal origin Vegetarian diets are not new but have only gradually gained acceptance as a balanced nutritional option. What problems are vegans at risk for? Vegetarian diets must be planned to ensure adequate calcium, iron, zinc, and vitamins B12 and D.

58 Nursing Assessment of Nutritional Status
Dietary history Physical, psychological, social, and medical data that may affect nutritional status Anthropometric data Height, weight (including weight patterns), and body composition Laboratory data Serum albumin, total lymphocyte count (TLC), creatinine/height index, nitrogen balance, mean corpuscular volume (MCV), and transferrin saturation Physical examination data The well-nourished person should have shiny and healthy-looking hair, bright and clear eyes, smooth facial skin with good color, smooth lips and tongue, and healthy teeth and gums. What are the signs of malnutrition? Body composition is related to the ratio of fat to lean muscle mass.

59 Figure 9-3

60 Weight Management and Eating Disorders
Most adults maintain a constant weight but must eat and exercise consistently on a daily basis Overweight: obese if weight is 20% or more above ideal body weight Underweight: weight is 15% to 20% or more below accepted weight standards Eating disorders fairly common among teenage girls and young women, and may persist into adulthood Changing eating patterns takes motivation, hard work, and a willingness to control behavior over a long period of time. Obesity is associated with which disorder?

61 Anorexia Nervosa An eating disorder characterized by self-imposed starvation Generally girls in their midteens, although young adult women and men sometimes develop the disorder Become obsessed with weight loss; distorted body image The young person with anorexia nervosa is often a perfectionist who uses food and exercise as a means of controlling the body. How often does death occur with anorexia nervosa?

62 Bulimia Characterized by periods of binge eating followed by purging
May alternate with periods of fasting Occurs more frequently than anorexia nervosa; also seen most often in young women People with bulimia are usually of normal weight or are even overweight. What are the clinical signs of bulimia?

63 Binge-Eating Disorder
The intake of excessive calories at least twice a week for 6 months The person with binge-eating disorder eats very rapidly, sometimes consuming as much as 20,000 calories in one sitting.

64 Nutritional Support with Supplemental Feedings
Sometimes a person’s nutritional needs cannot be met by oral feeding and a nutritional supplement is required Liquid or powdered milk, powdered whole eggs, and powdered egg albumin as concentrated protein sources Examples: Ensure, Compleat, Sustacal, Criticare HN, Pulmocare, Trauma Cal, Travasorb HN, and Travasorb Renal Liquid feedings can meet the nutritional requirements of patients who are unable to take solid food. What is the preferred method of meeting nutritional requirements?

65 Enteral Tube Feedings Bypass the mouth and deliver nutrients directly into the stomach or small intestine through inserted tubes Tubes can be inserted into the stomach, duodenum, or jejunum through the nose or through the abdominal wall Complications Nausea or vomiting, diarrhea, gastrointestinal bleeding, aspiration pneumonia, hyperkalemia, hyponatremia, hyperglycemia, or nutritional deficiency Dumping syndrome Patients who are unable to take in supplemental liquid feedings orally may require enteral tube feedings. What are some conditions that interfere with taking in liquids orally?

66 Figure 9-4

67 Parenteral Nutrition Peripheral parenteral nutrition
Intravenous therapy May be composed of dextrose (5%-10%), amino acids, vitamins, minerals, and electrolytes At most it supplies 1800 kcal/day Total nutritional requirements usually are not met with PPN therapy. What is the most kcal/day that PPN may supply?

68 Parenteral Nutrition Total parenteral nutrition
Used for patients who are unable to obtain adequate nutrition enterally or with PPN Can supply up to 4000 kcal/day Complications: pulmonary complications, injury to the veins and arteries surrounding the TPN catheter site, air embolism, infection, electrolyte imbalance, mineral deficiency, hyperglycemia, and, if treatment is ended suddenly, rebound hypoglycemia Patients with what disorders may benefit from this form of nutritional support? The solution is administered through a Hickman or Broviac-type catheter inserted into the superior vena cava.

69 Transitional Feeding Nutrition changed from one method to another
Important that it be done gradually Nutritional recovery syndrome my occur if given food too quickly Moderate in carbohydrates, low in sodium, lactose free, and supplemented with phosphorus and potassium What may cause hypophosphatemia? Refeeding of the malnourished patient disrupts the adaptive state of starvation and therefore must proceed slowly with close patient monitoring.

70 Transitional Feeding Parenteral to oral or enteral feeding
Continue the parenteral feeding; as patient is able to tolerate the oral or enteral feedings, parenteral feedings can be tapered off Enteral to oral feedings Change the enteral feeding from a continuous drip to an intermittent feeding; allows patient to get hungry


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