2Learning ObjectivesExplain 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.
3Anatomy and Physiology of the Gastrointestinal System
4Gastrointestinal System (GI tract or “gut”) The long, continuous tube that receives and transports food, absorbs nutrients, and eliminates waste products of digestionPrimary organsMouth, pharynx, esophagus, stomach, small intestine, and large intestineAccessory organsLiver, gallbladder, and pancreasRoles in food digestion even though not part of digestive tract
5Digestion and Absorption 92% to 97% of diet digested and absorbedWater, simple sugars, vitamins, minerals, and alcohol absorbed in their original formLipids, proteins, and complex sugars must be converted to simple forms before they are absorbed
6Digestion and Absorption HydrolysisWater splits complex molecules into smaller unitsEnzymesGovern the process of hydrolysis, along with bile and hydrochloric acidHelp break down food particles to their simplest form so nutrients can be absorbedFound throughout intestinal tract, except in the large intestineOnly water, salt, vitamins, and minerals are absorbed in the colon
7Regulators of the Gastrointestinal Tract Neural controlManaged by autonomic nervous system and nerve network in gut wall called the enteric nervous systemAutonomic system: sympathetic and parasympathetic nervesParasympathetic nerves stimulate digestive activitySympathetic nerves inhibit activityParasympathetic effect conveyed by vagus nerve: acid stimulation in stomach in response to sight/smell of foodEnteric nervous system receives information from receptors in gastric mucosa that are sensitive to acidity of the gastrointestinal tract and the feeling of fullness
8Regulators of the Gastrointestinal Tract Hormone secretionSecreted into the gastrointestinal tract to help regulate gastric pH, gastric motility, and appetiteStimulate the pancreas to secrete insulin and enzymes
9Digestive Process: Mouth Teeth grind and crush food into small particlesFood forms mass moistened and lubricated by salivaA secretion containing an enzyme known as amylase (ptyalin) digests any present starchMass, or bolus, then passed to the pharynx and through the esophagus by the process of swallowingPeristalsis moves the food rapidly through the esophagus into the stomachWhat are the three areas of the gastrointestinal system in which digestion of food occurs?
10Digestive Process: Stomach The mass is mixed with gastric secretionsActive chemical digestion is accomplished by the secretion of gastric juiceProduces average of 2000 to 2500 ml gastric juice dailyThe juice contains hydrochloric acid, enzymes, mucus, and the GI hormone gastrinAids in digestion by converting the mass to a semiliquid substance called chyme
11Digestive Process: Stomach Normally emptied in 1 to 4 hoursCarbohydrates leave the stomach most rapidly, followed by protein, and then fatValves (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 stomachWhat happens to the emptying of the stomach when a mixed diet has been consumed?
12Digestive Process: Small Intestine Divided into the duodenum, the jejunum, and the ileumMost digestion completed in duodenum; jejunum and ileum function mostly in the absorption of nutrientsThe remaining chyme is delivered to the large intestine
13Digestive Process: Large Intestine Water and electrolytes are absorbed, leaving a mass of wastes called fecesFecal mass is stored in the rectum, where it triggers the defecation reflexWhen anal sphincters relax, feces pass out of the body through the anus
14Mechanisms of Absorption Absorption is accomplished by the combination of the processes of diffusion and active transportDiffusionMovement of particles from an area of higher concentration to an area of lower concentrationActive transportRequires the input of energy for the movement of particles across a membrane against an energy gradientRequires a carrier proteinBest-known carrier is the intrinsic factor, which is responsible for the absorption of vitamin B12
15Mechanisms of Absorption Small intestinePrimary organ of absorption22 feet long and arranged in foldsSurface of folds covered with ﬁngerlike projections called villiAbsorb nutrients into the blood and lymph vessels that support themAbsorbs 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
16Nutrients: Carbohydrates Digestion begins in the mouth, where the enzyme amylase is releasedIn the stomach, amylase activity halted when it comes into contact with hydrochloric acidIf carbohydrates remain in the stomach long enough, hydrochloric acid reduces most to their simplest formStomach generally empties into the small intestine before this occurs, so most of the digestion of carbohydrates occurs within the small intestineMacronutrients 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.
17Nutrients: Carbohydrates In the small intestine, pancreatic amylase is released to continue carbohydrate digestionPass through the villi into the bloodstream, where carbohydrates carried by the portal vein to the liverFrom the liver, most of the glucose is transported to the tissuesSome stored for later use in the liver in the form of glycogen and in the muscleSome forms, particularly fiber, cannot be digested by humans and are excreted unchanged in the feces
18Nutrients: ProteinDigestion does not begin until it reaches the stomachSplit into smaller moleculesMost digestion occurs in the duodenumAlmost all of the protein is absorbed by the time it reaches the end of the jejunumOnly 1% of ingested protein found in the feces
19Nutrients: Fat Digestion begins in the stomach Gastric lipase An enzyme, breaks down the triglycerides that make up fat into fatty acids and glycerolMajor portion of fat digestion takes place in the small intestinePeristaltic action of small intestine, along with bile secreted by the liver, breaks down the larger fat globules into smaller particles
20Nutrients: Fluids, Vitamins, and Minerals Absorbed through the intestinal mucosaEach day about 8 L of fluid from the body pass back and forth across gut membrane to keep the nutrients in solutionVitamins and water pass unchanged from the small intestine into the blood by passive diffusionMineral absorption is a more active, complex process that takes place in several stages
21Factors Affecting Digestion Psychological stateLook, smell, and taste of food have effect on digestionEmotions such as fear, anger, and worry can inhibit peristalsis and depress gastric secretionsBacterial actionNeeded to help form vitamin K, vitamin B12, thiamine, and riboﬂavinProduce various gases, acids, and other toxic substancesFood processingWhat 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
22Energy Expenditure Measurement of energy expenditure Basal metabolic rate (BMR)Factors that can cause the metabolic rate to varyBody size and compositionPeriods of growthSecretion of hormonesTemperatureMenstrual cyclePregnancyIn 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?
23Energy Expenditure Energy measurements and calculations Calorie Standard unit for measuring energyAmount of heat energy needed to increase temperature of 1 g of water at standard temperature by 1° CMeasure of human energy expenditureDirect calorimetryIndirect calorimetryDoubly labeled waterWhat 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.
24CarbohydratesOrganic compounds consisting of carbon, hydrogen, and oxygenAll the sugars and starches that people eat and most types of fibersPlants manufacture and store carbohydrates as their chief source of energyGlucose main sugar in the blood and body’s basic fuel; serves as primary source of energyMost of the energy we require is consumed in the form of carbohydrates.What are the simplest sugars?
25CarbohydratesClassified according to the number of simple sugars or saccharidesMonosaccharides1 saccharideDisaccharides2 saccharidesOligosaccharides3 to 10 monosaccharidesPolysaccharides10 to 10,000 or more moleculesWhat are some examples of each classification of sugar? Food sources?
26Carbohydrates Metabolism Converted to glucose for immediate use by the body’s cells and to glycogen for storageSerum glucose level maintained at normal through the regular intake of nutrients, storage or breakdown of glycogen, glucogenesis, and gluconeogenesisNormal blood glucose levels: 70 to 100 mg/100 ml under fasting conditionsAfter a meal, blood glucose level may rise to130 mg/100 ml but returns to normal within 2 to 3 hoursDuring 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?
27Carbohydrates Dietary fiber A group of polysaccharides that act differently from other carbohydratesFound only in plant foods and are resistant to human digestive enzymesMajor digestive role is to help form a soft, firm stool and to aid in the process of eliminationTypesInsolubleSolubleWhat 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.
28Carbohydrates Functions of carbohydrates Recommended Dietary Allowance Major source of energy to body tissuesSole source of energy for the brainMaintain functional integrity of nerve tissueSpare fats from being used for metabolismPrecursors (basic building blocks) for other physiologic substancesRecommended Dietary AllowanceCarbohydrates 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.
29Lipids Include fats, oils, waxes, and related compounds May be solid or liquid formsInsoluble in waterContain carbon, hydrogen, and oxygenTriglycerides: most common fat found in foods of both animal and plant originFat metabolism uses more oxygen and releases more energy than either carbohydrate or protein metabolism.Triglycerides consist of how many fatty acids?
30Lipids Saturated fatty acids Unsaturated fatty acids Loaded with all the hydrogen atoms they can carrySolid at room temperatureUnsaturated fatty acidsDo not have all the hydrogen atoms they can carryLiquid at room temperatureFats 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.
31Lipid Transport and Storage Most are absorbed into the lymphatic system through the intestinal mucosaThe exception is certain fatty acids that are absorbed directly into the portal bloodFor fat to be digested, it must be emulsiﬁed, or pulled into suspension with digestive juicesBile (secretion of liver) needed to emulsify fat
32Lipid Transport and Storage Once emulsiﬁed, fats can be broken down and absorbedLipoproteinsProtein that transports lipids in the bloodstreamChylomicrons, 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?
33Lipid MetabolismA source of energy for most body tissues except the brain, blood cells, skin, and renal medullaLipolysisFat cells release glycerol and free fatty acidsLiver converts it to triglycerides or glucoseFree fatty acids bind to albumin for transportation in the blood and interstitial tissueMost lipids carried to liver for conversion to energy or for the synthesis of new triglyceridesThe 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 proteinDesaturation of fatty acidsCatabolism (breakdown) of triglycerides for use as energyHow does ketoacidosis occur?
34Recommended Dietary Allowance 20% to 35% of the adult diet should be composed of fatsUnsaturated fats rather than saturated fats minimize the risk of heart diseaseStudies have shown that Americans tend to consume too much fat.How can consuming too much fat affect the body?
35Food Sources of Fat Saturated fats Unsaturated fats Animal products: beef, dairy products, and eggsUnsaturated fatsVegetable oils, including corn oil, cottonseed oil, and safflower oilCattle and pigs are being bred to yield beef and pork that is lower in saturated fat.
36Lipid Function Store energy Maintain healthy skin and hair Carry fat-soluble vitaminsSupply essential fatty acidsPromote satietyCarbohydrates are the body’s main source of food energy, but fats are the most concentrated source.How many kilocalories per gram do fats supply?
37ProteinsBasic structure of a chain of amino acids that can form many different configurations and combine with other substancesContains carbon, hydrogen, oxygen, nitrogen, sulfur: sometimes metals, acids, lipids, polysaccharidesSimple proteinsMade of only amino acidsConjugated proteinsMade of amino acids in combination with other substances
38Proteins Amino acids Nine essential: must be obtained from the diet Body can manufacture enough of the other amino acids from the essential amino acidsComplete proteinContains all 9 essential amino acids in sufficient quantity and ratio for the body’s needsIncomplete proteinsLack one or more of the essential amino acidsThere 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.
39Protein Metabolism and Synthesis DeaminationProtein is broken down in the small intestine to the constituent amino acidsProtein synthesisControlled by DNA in the cellsDNA: provides the form to link up the exact combination of amino acids needed to form a particular proteinWhat 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.
40Protein DeficiencyThe body cannot store protein, so it needs to be eaten each dayIf protein intake is inadequate, nitrogen will be conserved by the kidneys, causing the urine nitrogen to be lowNitrogen in the urine is a good indicator of protein levels in the body.What are the signs and symptoms of protein deficiency?
41Evaluation of Protein Quality Should include both the quantity and the quality of the protein consumedEating a mixture of foods in a meal, if the quantity is sufficient, tends to provide all of the essential amino acidsThe 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%.
42Functions of ProteinsFurnish building blocks (amino acids) to build and repair tissueServe as an energy sourceHelp form enzymes, hormones, and other body fluids and secretionsAssist in the transport of fats, fat-soluble vitamins, and other substancesHelp maintain osmolarity of body fluids
43Recommended Dietary Allowance Should contribute 10% to 35% of the macronutrients in the adult dietThe recommended dietary reference intake for protein is 56 g/day for males and 46 g/day for females.
44Vitamins Fat soluble Water soluble Vitamins A, D, E, and K Usually absorbed in the body with other lipidsWater solubleB-complex group (thiamine, riboﬂavin, niacin, B6, folate, B12, pantothenic acid, and biotin) and vitamin C (ascorbic acid)Readily excreted from the bodyVitamins 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.
45MineralsEnzyme regulation, maintain acid-base balance and osmotic pressure, and maintain nerve and muscular irritabilityMacromineralsCalcium, phosphorus, magnesium, sulfur, sodium, chloride, potassiumMicrominerals or trace elementsIron, zinc, iodine
46Minerals Ultratrace elements Ionized forms Selenium, chromium, copper, manganese, molybdenum, boron, cobaltIonized formsSodium, potassiumConstituents of organic compoundsPhospholipids, hemoglobinMinerals 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.
47WaterLargest component of the body and tissues; essential to all body life processesIntake of water is controlled by thirstAlso ingested through foodThe body cannot store waterEssential that all living things replenish water daily to maintain health and efficiencyWhat 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.
48WaterThe longest that people can live without water is approximately 4 daysAdults generally should take in about 2500 ml, or 2 to 3 quarts, per day
49Age-Related Changes Energy Normal decline in metabolism and common decrease in physical activity, lower energy needs with ageOften reduce the kilocalories taken in per dayCan result in inadequate intake of essential nutrientsPsychosocial factors also may lead to poor nutrition in the older personDepression, cognitive impairment, and lonelinessThe 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?
50Nutritional Care of the Older Adult Dietary planningMeals need to be appealing, taking into consideration individual likes and dislikes, and should be tasteful and fillingNutrition programsCommunity-based programs, administered by public and private agencies, provide hot, nutritious meals to older adultsProblems 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?
51Nutritional Care of the Older Adult Nutritional needs during prolonged illnessIncreased nutritional needs during illnessNasogastric tube feedings or parenteral nutrition may be requiredNutritional care in institutional settingsPeriodic reassessment of nutritional status is criticalWhat 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.
52MyPyramidBased on recommendations from the 2005 USDA Dietary Guidelines for AmericansIncludes figure climbing the steps of the pyramid to emphasize exercise in addition to nutritionColored 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 pyramidEnter age, gender, and activity level
54Food LabelingPeople have expressed an increased need to be informed about what they are eatingMany more foods are now labeled so that the average person can make determinations about the quality and quantity of the nutrients consumed
55National Guidelines for Diet Planning Many guidelines are available on proper nutrition to maintain health and prevent diseaseSurgeon General’s Report on Nutrition and Health can be used as a basis for dietary planning (Table 9-14)
57Vegetarian DietsMany vegetarians eat all foods except red meat, although some exclude poultry and fish as wellLactovegetarian dietIncludes milk, cheese, and other dairy products but excludes meat, fish, poultry, and eggsLacto-ovo-vegetarian dietIncludes dairy products and eggs but excludes meat, fish, and poultryVeganConsumes no foods of animal originVegetarian 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.
58Nursing Assessment of Nutritional Status Dietary historyPhysical, psychological, social, and medical data that may affect nutritional statusAnthropometric dataHeight, weight (including weight patterns), and body compositionLaboratory dataSerum albumin, total lymphocyte count (TLC), creatinine/height index, nitrogen balance, mean corpuscular volume (MCV), and transferrin saturationPhysical examination dataThe 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.
60Weight Management and Eating Disorders Most adults maintain a constant weight but must eat and exercise consistently on a daily basisOverweight: obese if weight is 20% or more above ideal body weightUnderweight: weight is 15% to 20% or more below accepted weight standardsEating disorders fairly common among teenage girls and young women, and may persist into adulthoodChanging eating patterns takes motivation, hard work, and a willingness to control behavior over a long period of time.Obesity is associated with which disorder?
61Anorexia NervosaAn eating disorder characterized by self-imposed starvationGenerally girls in their midteens, although young adult women and men sometimes develop the disorderBecome obsessed with weight loss; distorted body imageThe 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?
62Bulimia Characterized by periods of binge eating followed by purging May alternate with periods of fastingOccurs more frequently than anorexia nervosa; also seen most often in young womenPeople with bulimia are usually of normal weight or are even overweight.What are the clinical signs of bulimia?
63Binge-Eating Disorder The intake of excessive calories at least twice a week for 6 monthsThe person with binge-eating disorder eats very rapidly, sometimes consuming as much as 20,000 calories in one sitting.
64Nutritional Support with Supplemental Feedings Sometimes a person’s nutritional needs cannot be met by oral feeding and a nutritional supplement is requiredLiquid or powdered milk, powdered whole eggs, and powdered egg albumin as concentrated protein sourcesExamples: Ensure, Compleat, Sustacal, Criticare HN, Pulmocare, Trauma Cal, Travasorb HN, and Travasorb RenalLiquid feedings can meet the nutritional requirements of patients who are unable to take solid food.What is the preferred method of meeting nutritional requirements?
65Enteral Tube FeedingsBypass the mouth and deliver nutrients directly into the stomach or small intestine through inserted tubesTubes can be inserted into the stomach, duodenum, or jejunum through the nose or through the abdominal wallComplicationsNausea or vomiting, diarrhea, gastrointestinal bleeding, aspiration pneumonia, hyperkalemia, hyponatremia, hyperglycemia, or nutritional deﬁciencyDumping syndromePatients 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?
67Parenteral Nutrition Peripheral parenteral nutrition Intravenous therapyMay be composed of dextrose (5%-10%), amino acids, vitamins, minerals, and electrolytesAt most it supplies 1800 kcal/dayTotal nutritional requirements usually are not met with PPN therapy.What is the most kcal/day that PPN may supply?
68Parenteral Nutrition Total parenteral nutrition Used for patients who are unable to obtain adequate nutrition enterally or with PPNCan supply up to 4000 kcal/dayComplications: 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 hypoglycemiaPatients 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.
69Transitional Feeding Nutrition changed from one method to another Important that it be done graduallyNutritional recovery syndrome my occur if given food too quicklyModerate in carbohydrates, low in sodium, lactose free, and supplemented with phosphorus and potassiumWhat may cause hypophosphatemia?Refeeding of the malnourished patient disrupts the adaptive state of starvation and therefore must proceed slowly with close patient monitoring.
70Transitional 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 offEnteral to oral feedingsChange the enteral feeding from a continuous drip to an intermittent feeding; allows patient to get hungry