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Nutrition for Nurses

17.1 Assess and Analyze the Impact of Nutrition on the Gastrointestinal System

Nutrition for Nurses17.1 Assess and Analyze the Impact of Nutrition on the Gastrointestinal System

Learning Outcomes

By the end of this section, you should be able to:

  • 17.1.1 Recognize the normal function of the gastrointestinal system.
  • 17.1.2 Recognize cues of nutritional impact on the gastrointestinal system.
  • 17.1.3 Analyze cues of nutritional impact on the gastrointestinal system.

Normal Function of the Gastrointestinal System

The gastrointestinal system comprises the organs in the upper gastrointestinal tract—the mouth, esophagus, stomach, and duodenum—and the organs in lower gastrointestinal tract—the small intestine, large intestine (or colon), rectum, and anus. The gastrointestinal system is aided by the teeth, tongue, salivary glands, and the pancreas, liver, and gallbladder, which are also known as ancillary digestive organs. The sensory system, the nervous system, the mucous membranes, and glands (digestive and adrenal) also have roles to play.

There are four main functions of the gastrointestinal system: ingestion, digestion, absorption, and metabolism. Ingestion is the swallowing and absorbing of substances into the body. This process starts with the sensory organs before food even enters the oral cavity: The smell or sight of appealing food can trigger the salivary glands to release saliva. That process, combined with hunger, can increase the desire to ingest the food. Once the food is inside the mouth, its taste, sensed through the papillae on the tongue, can either encourage or inhibit its further ingestion. Foods that register an unappetizing taste encourage expulsion from the oral cavity.

Digestion occurs when the body breaks down what is ingested into absorbable substances. This, too, starts in the oral cavity. The tongue and teeth start the digestion of food using mostly mechanical and some chemical processes known collectively as mastication. Mastication employs the use of the tongue for mechanical compression, abrasion, and distortion; secretion of mucins and lingual lipase, which assist in breaking down lipids; and manipulation to assist with movement during chewing and swallowing (Ogobuiro et al., 2023). The teeth are used strictly for mechanical processes during mastication as they cut, tear, grind, and chew food to break it down physically into smaller pieces.

Chemical digestion and lubrication in the oral cavity to aid in food movement are accomplished by the tongue and salivary glands. There are three pairs of salivary glands in the mouth: the parotid glands, which release salivary amylase to break down complex carbohydrates; sublingual glands, which release a mucus secretion that acts as a buffer and a lubricant; and the submandibular glands, which release a mixture of salivary amylase, buffers, and glycoproteins called mucins (Figure 17.2) (Ogobuiro et al., 2023).

The food is broken down and lubricated enough during mastication to be swallowed and moved to the next phase of digestion. The swallowing reflex is aided by the tongue, allowing food to travel down the esophagus via peristalsis and empty into the stomach through the lower esophageal sphincter.

A diagram of the mouth illustrating where the different glands and ducts are located. The parotid salivary gland is located at the back of the mouth; it is connected to the parotid duct. The submandibular salivary gland is located toward the back of the bottom of the mouth, below the teeth. It is connected to the submandibular duct. The sublingual salivary gland is also located below the teeth, but more toward the front of the mouth. It is connected to the sublingual ducts.
Figure 17.2 The salivary glands aid in chemical breakdown of food in the oral cavity. (credit: modification of work from Anatomy and Physiology 2e. attribution: Copyright Rice University, OpenStax, under CC BY 4.0 license)

Some digestion, both mechanical and chemical, occurs in the stomach, which also temporarily stores food. Food exits the stomach as chyme, a blend of gastric juices and digested food particles. The stomach also synthesizes proteins that are needed for vitamin absorption and microbial defenses, propagates the peristaltic reflex, and releases intrinsic factor from the parietal cells, which enables the small intestine to absorb vitamin B12 (Hsu et al., 2023). When chyme exits the stomach, simple carbohydrates have been digested. Larger molecules such as complex carbohydrates, fats, and proteins have not yet been broken down.

The duodenum breaks down larger molecules. In the duodenum, at the sphincter of Oddi, there is a release of digestive secretions by the ancillary organs (Ogobuiro et al., 2023), specifically from the gallbladder and the pancreas. The pancreas releases active alpha-amylase, colipase, and lipase, and the gallbladder releases bile, produced in the liver, to break down fats, proteins, and complex carbohydrates.

Absorption refers to the taking in of the broken-down substances into the cells. Very few substances are absorbed by the stomach. The small intestine handles 90% of food absorption as food travels through its three segments, the duodenum, jejunum, and ileum (Ogobuiro et al., 2023). The innermost layer of the mucosa of the small intestine is composed of absorptive cells known as enterocytes, goblet cells, and enteroendocrine cells (Fish & Burns, 2022). Enterocytes are effective at absorption because each one has around 3,000 microvilli that expand their available surface area (Figure 17.3).

Absorptive cells line the small intestine's enterocyte. Some absorptive cells contain goblet cells. The absorbative cells have many tiny microvilli, also known as a brush border. Multiple long, vertical lacteal  branch off from the lymphatic vessel; these are surrounded by a capillary and artery. The indentation between each lacteal branch is the intestinal crypt. Above the lymphatic vessel is the muscularis mucosae; below it is the duodenal gland.
Figure 17.3 In the small intestine, goblet cells have microvilli to better absorb nutrients. (credit: modification of work from Anatomy and Physiology 2e. attribution: Copyright Rice University, OpenStax, under CC BY 4.0 license)

The duodenum is the site for iron absorption and some vitamin B9 (folate) absorption, but the major site for vitamin B9 absorption is the jejunum (Fish & Burns, 2022). Minerals and vitamins A, D, E, and K are absorbed through the small intestine. The small intestine absorbs 90% of the water from digested food (Fish & Burns, 2022). The last segment of the small intestine, the ileum, is responsible for the absorption of bile salts and vitamin B12 (cobalamin;) (Fish and Burns, 2022). Each broken-down substance is now in a new, more usable form for use by the body's metabolic processes (Table 17.1).

Macronutrient Before Digestion After Digestion
Carbohydrate: polysaccharides (starchy foods) Amylose Monosaccharides
Carbohydrate: disaccharides Lactose, sucrose, maltose, trehalose Glucose, fructose, galactose
Protein Large-chain amino acids joined by peptide bonds Separate amino acids and peptides (oligopeptides, dipeptides, tripeptides)
Fat Triglycerides Monoglycerides, fatty acids
Table 17.1 Nutrients Before and After Digestion for the Body’s Metabolic Use (source: Fish & Burns, 2022)

The last part of the absorption process takes place in the large intestine. It has three main functions in digestion: absorption of the remaining water and electrolytes, absorption and production of vitamins, and formation and movement of feces to the rectum for elimination. The first portion of the large intestine, the ascending colon, removes any remaining water and key nutrients from the indigestible material passing through it while solidifying this waste to form stool.

During this part of digestion, water osmosis causes absorption of the remaining water, sodium is absorbed via sodium channels, potassium absorption is regulated by its concentration in the lumen, and chloride and bicarbonate ions are exchanged. In addition, the large intestine houses trillions of bacteria, which produce many vitamins, including vitamin K, B vitamins, and biotin, through fermentation (Azzouz & Sharma, 2023).

Metabolism refers to the chemical processes by which the body converts absorbed substances to energy. Catabolic reactions release large amounts of protons, which are transported to mitochondria in the cells to produce adenosine triphosphate (ATP), the body’s chemical carrier of energy (Sanchez Lopez de Nava & Raja, 2022). An imbalance between energy spent and energy used, or between anabolism and catabolism, can result in obesity or cachexia (Sanchez Lopez de Nava & Raja, 2022). Obesity is clinically defined as an excessive or abnormal accumulation of fat in the body that can increase an individual’s health risks. Cachexia refers to muscle loss with or without fat mass loss.

For these processes to take place effectively and provide balanced nutrition and appropriate energy, the individual must first ingest the proper mix of the required nutrients and water.

Assessment of the Normal Gastrointestinal System

Assessment of the gastrointestinal organs and normal expected findings are explained in detail in The Digestive Process. This section will cover expected physical assessment findings in clients who demonstrate normal nutritional status. Overall normal physical assessment findings in addition to normal gastrointestinal organ–specific findings can help confirm a fully functioning gastrointestinal system (Table 17.2).

Organ Assessed Expected Findings
  • Symmetric, soft, moist, smooth textured, uniform in color and with expected color for race (pink for fairer-skinned and darker for darker-skinned individuals), symmetrically contoured, symmetrically pursed when individual is asked to purse the lips
Buccal mucosa and inner lips
  • Uniform pink or freckled brown in darker-skinned individuals, moist (may be slightly drier in older clients because of decreased salivation), glistening, smooth, elastic texture
  • Moist and firm without retraction from the teeth; older clients may show some hyperpigmentation and receding of the gumline
  • Central resting position in the mouth but able to move freely; no tenderness, swelling, or lesions; smooth with lateral margins and raised papillae (taste buds); base should be smooth and prominent with veins and no ulcerations
  • Smooth and pink at the posterior wall; uvula midline at the back of the soft palate and freely movable; tonsils (if present) smooth, colored appropriately for race, of normal size (usually larger in children than in adults) or not visible, without discharge; gag reflex present
  • Smooth and white with shiny enamel; older adults may have teeth staining, chipping, erosions, or abrasions due to the aging process and wearing of teeth; older children and adults may have dental appliances; any dentures or bridges should be smooth and intact
    Expected number of teeth: adults, 32; children by the age of 3 years, 20; children and young adults aged 6–20 years can have a varying number as they lose primary teeth and gain permanent teeth; newborns should not have teeth
Soft palate and hard palate
  • Light>Light pink or colored appropriately for race; the soft palate should be smooth and the hard palate more irregularly textured; newborns may have Epstein pearls, Bohn nodules, or gingival cysts
Abdomen: inspection
  • Skin: intact, uniform in color and consistent with race, no ecchymosis or jaundice, silver–white striae (stretch marks) may be present (may be purple–pink in pregnant client), surgical scars may be present
    Flat, rounded but not distended or scaphoid (sunken); no protrusions or evidence of spleen or liver enlargement; no visible vascular patterns (except in pregnancy); respirations should cause symmetric movements of the abdomen; in very lean client, aortic pulsations may be visible at the epigastric area, and peristalsis may also be visible; umbilical stump should be present in newborns
Abdomen: auscultation
  • Bowel sounds present in all quadrants, low pitched and gurgling and occurring at a rate of 2–5 per minute, lasting from less than 1 second to several seconds each; no bruits or friction rub; no succussion splash
Abdomen: percussion
  • Dull, flat, or decreased sounds over organs; more tympanitic (louder and higher pitched) over areas of air or gas
Abdomen: palpation
  • No pain, crepitus, tenderness, bulging, masses, inflammation, or muscle guarding; deep palpation should reveal normal-sized organs without masses, nodules, or tenderness
  • Skin intact, hairless, and slightly moister, coarser, and more pigmented than surrounding skin; patent anal canal
  • No masses or fissures; prostate in male client should be firm, smooth, not enlarged
Table 17.2 Expected Normal Findings During Physical Assessment of the Gastrointestinal System (sources: Diaz de Ortiz & Mendez, 2022; Gantan & Wiedrich, 2022; Mealie et al., 2022)

In addition to assessing individual organs, the nurse should conduct a general physical assessment, being alert for specific findings that indicate adequate nutrition (Table 17.3). Such findings also help demonstrate that the gastrointestinal system is functioning correctly.

Feature Assessed Expected Findings
General appearance Alert, conscious, and ambulatory within the confines of client’s ability; no general emaciation
Height, weight, and body mass index Body mass index of 18.5–24.9 kg/m2; 30 and over is considered obesity, with Class 3 obesity being 40 or greater
Vital signs Vital signs that fall within expected ranges can indicate good nutritional status, but many pathologies can affect vital signs without regard to nutrition. Blood pressure and pulse can indicate hydration status; low blood pressure (less than 90/60 mm Hg) and tachycardia (heart rate greater than 100 beats per minute) can indicate hypovolemia
Eyes No pallor of the palpebral conjunctiva, icterus (yellowing) of the sclera, Bitot’s spots (oval or triangular patches on the conjunctiva of built-up keratin), xerosis (dryness) of the cornea, or xanthelasmas (yellow plaques on or near the eyelids)
Skin No xeroderma (dry skin), petechiae, purpura, ecchymosis, jaundice, carotenoderma (yellow–orange skin discoloration), poorly healing wounds, pigmentation or rashes in sun-exposed areas (such as around the neck or on the extremities, where pigmentation might look like gloves or stockings), xanthomas (localized lipid deposits), or loss of subcutaneous adipose tissue
Hair No dryness, brittleness, or unexpected discoloration; not easy to pluck; no patches of baldness or extreme thinness
Nails No dryness, brittleness, discoloration, clubbing, or koilonychia (soft nails that are concave in the center and appear to be “scooped out”)
Extremities No edema, weakness, paresthesia, sensation loss, bowing, ulcerations, poorly healing wounds, neuropathies, or muscle atrophy or wasting
Odor No unusual odors; fruity acetone, musty, and sweet, burnt sugary odors can indicate specific nutritional issues due to pathologies
Function Ability to perform functions at the client’s baseline for their age; deficits from baseline or, in infants and children, delays in development, growth, or weight can indicate poor nutritional status
Table 17.3 Expected Normal Findings During General Physical Assessment (sources: Castera & Borhade, 2022; Cleveland Clinic, n.d.-b; Feroze & Kaufman, 2023; Johnson, 2021; Kesari & Noel, 2023; Rosenthal, 2020; Schneider & Gibbs, 2022; UPMC, n.d.)

Nutritional Deficiencies Related to Abnormal Assessment Findings in the Gastrointestinal System

Abnormal findings in an assessment of the gastrointestinal system and other systems can indicate the presence of disease or nutritional deficit. To best plan nutritional strategies for the client, the nurse should know what each abnormal finding, in conjunction with laboratory results and dietary recall, could indicate. Some abnormal findings and nutritional deficiencies and toxicities related to them are shown in Table 17.4.

Organ Assessed Abnormal Findings Nutritional Deficiency or Toxicity
Lips Fissures, crusts, or scales on the lips or in the corners of the lips, cracked lips, angular cheilitis Deficiency of vitamin B1 (thiamine), vitamin B12 (cobalamin), and/or iron
Tongue Inflammation of the tongue Deficiency of vitamin B2 (riboflavin) and/or B3 (niacin)
Loss of taste Deficiency of zinc
Halitosis Deficiency of vitamin B12 (cobalamin)
Red, painful tongue that has a burning sensation Deficiency of iron
Gums/mouth Ulcerative gingivitis Deficiency of vitamin B2 (riboflavin) and/or B3 (niacin)
Hemorrhagic gingivitis, painful mouth ulcers Deficiency of vitamin B12 (cobalamin)
Bleeding gingivitis Deficiency of vitamin C
Stomatitis (mouth inflammation) Deficiency of vitamin B complex
Salivary gland dysfunction, dysphagia Deficiency of iron
Recurrent aphthous stomatitis (canker sores) Deficiency of zinc
Salivary glands Dry salivary glands Dehydration or iron deficiency
Teeth Pits, grooves, or missing areas in enamel of the teeth, giving teeth a translucent appearance Deficiency of vitamin A
Periodontal disease Deficiency of vitamin B6 (pyridoxine) and/or B12 (cobalamin)
Abnormal bone patterns and shapes Deficiency of vitamin D
Dental caries (cavities) Deficiency of vitamin D and/or fluoride
Oropharynx Recurrent tonsillitis Deficiency of vitamin D
Pharyngitis Deficiency of vitamin B2 (riboflavin)
Inflammation of the hard and soft palates Deficiency of iron, vitamin B2 (riboflavin), B6 (pyridoxine), B9 (folate), and/or B12 (cobalamin), D, and zinc
Abdomen Constipation (hypoactive bowel sounds, decreased frequency of bowel movements, hard stools, straining with bowel movements, increased flatus, mild abdominal distention, mild abdominal tenderness) Deficiency of potassium, magnesium, vitamin B9 (folate), fiber, and/or fluid volume
Diarrhea (hyperactive bowel sounds, increased frequency of bowel movements, loose or watery stools, increased flatus, abdominal tenderness, symptoms of fluid volume deficit from losses) Deficiency of vitamin B3 (niacin) or excessive intake of potassium
Abdominal muscle pain and cramping Deficiency of magnesium, potassium, sodium, vitamin B1 (thiamine), vitamin D, and/or calcium
Anus Hemorrhoids and fissures (caused by chronic constipation and straining to pass stools) Deficiency of fiber and/or fluid volume
General appetite/ weight Loss of appetite Deficiency of zinc
Weight loss Deficient caloric intake, protein deficiency, or impaired absorption
Skin Skin discoloration Excessive intake of protein, carotene-containing foods, or supplements (vitamin A), causing diffuse hyperpigmentation, or excessive intake of both protein and zinc, causing carotenoderma
Ecchymosis Deficiency of vitamin C, vitamin K, or zinc
Muscle Muscle pain, cramps Deficiency of magnesium, potassium, sodium, vitamin B1 (thiamine), vitamin D, and/or calcium
Eyes Pallor Deficiency of iron, protein, or vitamin B6 (pyridoxine), B9 (folate), B12 (cobalamin), or C
Bitot’s spots, xerosis Deficiency of vitamin A
Xanthelasmas Excessive caloric intake, obesity, or hypercholesterolemia
Hair Dry hair Deficiency of vitamin A or E
Brittle hair Deficiency of vitamin B7 (biotin)
Discolored, easily pluckable hair; hair loss Deficiency of protein or iron; overall severe malnutrition
Nails Dry and brittle nails Deficiency of vitamin B7 (biotin), zinc, or protein
Nail discoloration Overall poor nutritional status
Koilonychia Deficiency of iron, causing anemia
Extremities Edema Deficiency of vitamin B1 (thiamine) or protein; excessive sodium
Paresthesia, muscle weakness Deficiency of vitamin B1 (thiamine), B6 (pyridoxine), B12 (cobalamin), or E
Loss of sensation Deficiency of vitamin B12 (cobalamin) or E
Muscle atrophy and wasting Severe malnutrition
Bowing of the legs (caused by rickets) Deficiency of vitamin D
Table 17.4 Relationship of Abnormal Assessment Findings and Nutritional Deficiencies or Toxicities (sources: American Dental Association, 2023; Cleveland Clinic, n.d.-a; Gold & Schoenhaus, 2023; Hakes, 2021; Johnson, 2022; Kesari & Noel, 2023; Mount Sinai Icahn School of Medicine, n.d.; Plewa & Chatterjee, 2022; Sawar et al., 2021; Stewart, n.d.)

Unfolding Case Study

Part A

Read the following clinical scenario and then answer the questions that follow. This case study will evolve throughout the chapter.

Mrs. Azan tells the nurse that she has been having muscle weakness and cramping, abdominal pain, mouth and tongue swelling, and sores in her mouth. When the nurse assesses Mrs. Azan, the nurse finds that she has angular cheilitis, multiple canker sores in her buccal areas, a red and swollen tongue, and general pallor.

Based on both the objective and subjective assessment findings, what would the nurse rule out as a potential deficiency being experienced by this client?
  1. Potassium
  2. Magnesium
  3. Vitamin B12
  4. Vitamin A
Based on Mrs. Azan’s presentation, which additional laboratory test should the nurse expect the health care provider to order?
  1. Iron
  2. Vitamin D
  3. Calcium
  4. Vitamin E

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