Metabolic and Nutritional Disorders
INTRODUCTION
Metabolism is the physiologic process that allows cells to transform food into energy and continually rebuild body cells. Metabolism has two phases: catabolism and anabolism. In catabolism, the energy-producing phase of metabolism, the body breaks down large food molecules into smaller ones; in anabolism, the tissue-building phase, the body converts small molecules into larger ones (such as antibodies to keep the body capable of fighting infection). Both phases are accomplished by means of a chemical process using energy. A wide range of nutrients is metabolized to meet the body’s needs. (See Essential nutrients and their functions.) A person’s protein, vitamin, and mineral requirements usually remain the same as he ages, although calorie needs decline. Diminished activity may lower energy requirements by almost 200 calories per day for men and women ages 51 to 75, 400 calories per day for women older than age 75, and 500 calories per day for men older than age 75.
CARBOHYDRATES: PRIMARY ENERGY SOURCE
The body gets most of its energy by metabolizing carbohydrates, especially glucose. Glucose catabolism proceeds in three phases:
Glycolysis, a series of chemical reactions, converts glucose molecules into pyruvic or lactic acid.
The citric acid cycle removes ionized hydrogen atoms from pyruvic acid and produces carbon dioxide.
Oxidative phosphorylation traps energy from the hydrogen electrons and combines the hydrogen ions and electrons with oxygen to form water and the common form of biological energy, adenosine triphosphate (ATP).
Other essential processes in carbohydrate metabolism include glycogenesis—the formation of glycogen, a storage form of glucose—which occurs when cells become saturated with glucose-6-phosphate (an intermediate product of glycolysis); glycogenolysis, the reverse process, which converts glycogen into glucose-6-phosphate in muscle cells and liberates free glucose in the liver; and gluconeogenesis, or “new” glucose formation from protein amino acids or fat glycerols.
A complex interplay of hormonal and neural controls regulates glucose metabolism. Hormone secretions of five endocrine glands dominate this regulatory function:
Alpha cells of the islets of Langerhans secrete glucagon, which increases the blood glucose level by stimulating phosphorylase activity to accelerate liver glycogenolysis.
Beta cells of the islets of Langerhans secrete the glucose-regulating hormone insulin, which assists in glucose transport across cell membranes and storage of excess glucose as fat.
The adrenal medulla, as a physiologic response to stress, secretes epinephrine, which stimulates liver and muscle glycogenolysis to increase the blood glucose level.
Corticotropin and glucocorticoids also increase blood glucose levels. Glucocorticoids accelerate gluconeogenesis by promoting the flow of amino acids to the liver, where they’re synthesized into glucose.
Human growth hormone (hGH) limits the fat storage and favors fat catabolism; consequently, it inhibits carbohydrate catabolism and thus raises blood glucose levels.
Thyroid-stimulating hormone and thyroid hormone have mixed effects on carbohydrate metabolism and may raise or lower blood glucose levels.
FATS: CATABOLISM AND ANABOLISM
The breaking up of triglycerides—lipolysis— yields fatty acids and glycerol. Betaoxidation breaks down fatty acids into acetyl coenzyme A, which can then enter the citric acid cycle; glycerol can also undergo gluconeogenesis or enter the glycolytic pathways to produce energy. Conversely, lipogenesis is the chemical formation of fat from excess carbohydrates and proteins or from the fatty acids and glycerol products of lipolysis. Adipose tissue is the primary storage site for excess fat and thus is the greatest source of energy reserve. Certain unsaturated fatty acids are necessary for synthesis of vital body compounds. Because the body can’t produce these essential fatty acids, they must be provided through diet. Insulin, hGH, catecholamines, corticotropin, and glucocorticoids control fat metabolism in an inverse relationship with carbohydrate metabolism; large amounts of carbohydrates promote fat storage, and deficiency of available carbohydrates promotes fat breakdown for energy needs.
PROTEINS: ANABOLISM
The primary process in protein metabolism is anabolism. Catabolism is relegated to a supporting role in protein metabolism—a reversal of the roles played by these two processes in carbohydrate and fat metabolisms. By synthesizing proteins—the tissue-building foods—the body derives substances essential for life (such as
plasma proteins) and can reproduce, control cell growth, and repair itself. However, when carbohydrates or fats are unavailable as energy sources, or when energy demands are exceedingly high, protein catabolism converts protein into an available energy source. Protein metabolism consists of many processes, including:
plasma proteins) and can reproduce, control cell growth, and repair itself. However, when carbohydrates or fats are unavailable as energy sources, or when energy demands are exceedingly high, protein catabolism converts protein into an available energy source. Protein metabolism consists of many processes, including:
Essential nutrients and their functions
Nutrients are required for the body to work properly and avoid disease.
Nutrients | Functions |
Carbohydrates | ▪ Energy source |
Fats and essential fatty acids | ▪ Energy source; essential for growth, normal skin, and membranes |
Proteins and amino acids | ▪ Synthesis of all body proteins, growth, and tissue maintenance |
Water-soluble vitamins: | |
▪ Ascorbic acid (C) ▪ Thiamine (B1) ▪ Riboflavin (B2) ▪ Niacin ▪ Vitamin B12 ▪ Folic acid | ▪ Collagen synthesis, wound healing, antioxidation ▪ Coenzyme in carbohydrate metabolism ▪ Coenzyme in energy metabolism ▪ Coenzyme in carbohydrate, fat, energy metabolism, and tissue metabolism ▪ Deoxyribonucleic acid (DNA) and ribonucleic acid synthesis; erythrocyte formation. ▪ Coenzyme in amino acid metabolism; heme and hemoglobin formation; DNA synthesis; lowering homocysteine levels |
Fat-soluble vitamins: | |
▪ Vitamin A ▪ Vitamin D ▪ Vitamin E ▪ Vitamin K | ▪ Vision in dim light, mucosal epithelium integrity, tooth development, endocrine function ▪ Regulation of calcium and phosphate absorption and metabolism; renal phosphate clearance; musculoskeletal function ▪ Antioxidation; essential for muscle, liver, and red blood cell integrity ▪ Blood clotting (catalyzes synthesis of prothrombin by liver); skeletal function |
Deamination—a catabolic and energy-producing process occurring in the liver with the splitting off of the amino acid to form ammonia and a keto acid
Transamination—anabolic conversion of keto acids to amino acids
Urea formation—a catabolic process occurring in the liver, producing urea, the end product of protein catabolism
The male hormone testosterone and hGH stimulate protein anabolism; corticotropin prompts secretion of glucocorticoids, which, in turn, facilitate protein catabolism. Normally, the rate of protein anabolism equals the rate of protein catabolism—a condition known as nitrogen balance (because ingested nitrogen equals nitrogen waste excreted in urine, feces, and sweat). When excessive catabolism causes
the amount of nitrogen excreted to exceed the amount ingested, a state of negative nitrogen balance exists—usually the result of starvation and cachexia or surgical stress.
FLUID AND ELECTROLYTE BALANCE
A critical component of metabolism is fluid and electrolyte balance. Water is an essential body substance and constitutes almost 60% of an adult’s body weight and more than 75% of a neonate’s body weight. In both older and obese adults, the ratio of water to body weight drops; children and lean people have a higher proportion of water in their bodies.
Body fluids can be classified as intracellular (or cellular) or extracellular. Intracellular fluid constitutes about 40% of total body weight and 60% of all body fluid; it contains large quantities of potassium and phosphates but very little sodium and chloride. Conversely, extracellular fluid (ECF) contains mostly sodium and chloride but very little potassium and phosphates. Incorporating interstitial, cerebrospinal, intraocular, and GI fluids and plasma, ECF supplies cells with nutrients
and other substances needed for cellular function. The many components of body fluids have the important function of preserving osmotic pressure and acid-base and anion-cation balance.
and other substances needed for cellular function. The many components of body fluids have the important function of preserving osmotic pressure and acid-base and anion-cation balance.
Homeostasis is a stable state—the equilibrium of chemical and physical properties of body fluid. Body fluids contain two kinds of dissolved substances: those that dissociate in solution (electrolytes) and those that don’t. For example, glucose, when dissolved in water, doesn’t break down into smaller particles; but sodium chloride dissociates in solution into sodium cations (+) and chloride anions (-). The composition of these electrolytes in body fluids is electrically balanced so the positively charged ions (cations: sodium, potassium, calcium, and magnesium) equal the negatively charged ions (anions: chloride, bicarbonate, sulfate, phosphate, proteinate, and carbonic and other organic acids). Although these particles are present in relatively low concentrations, any deviation from their normal levels can have profound physiologic effects.
ELDER TIPInstitutionalized older people are at particularly high risk for dehydration because of their diminished thirst perception and any combination of physical, cognitive, speech, mobility, and visual impairment.
In homeostasis—an ever-changing but balanced state—water and electrolytes and other solutes move continually between cellular and extracellular compartments. Such motion is made possible by semipermeable membranes that allow diffusion, filtration, and active transport. Diffusion refers to the movement of particles or molecules from an area of greater concentration to one of lesser concentration. Normally, particles move randomly and constantly until the concentrations within given solutions are equal. Diffusion also depends on permeability, electrical gradient, and pressure gradient. Particles, however, can’t diffuse against any of these gradients without energy and a carrier substance (active transport). ATP is released from cells to aid particles needing energy to pass through the cell membrane.
The diffusion of water from a solution of low concentration to one of high concentration is called osmosis. The pressure that develops when a selectively permeable cell membrane separates solutions of different strengths of concentrations is known as osmotic pressure, expressed in terms of osmols or milliosmols (mOsm). Osmotic activity is described in terms of osmolality—the osmotic pull exerted by all particles per unit of water, expressed in mOsm/kg of water—or osmolarity, when expressed in mOsm/L of solution.
The normal range of body fluid osmolality is 285 to 295 mOsm/kg. Solutions of 50 mOsm above or below the high and low points of this normal range exert little or no osmotic effect (isosmolality). A solution below 240 mOsm contains a lower particle concentration than plasma (hypo-osmolar), whereas a solution over 340 mOsm has a higher particle concentration than plasma (hyperosmolar).
Rapid I.V. administration of isosmolar solutions to patients who are debilitated, are very old or very young, or have cardiac or renal insufficiency could lead to ECF volume overload and induce pulmonary edema and heart failure because particulate concentration is the same as plasma, so fluid shifting into and out of cells will occur.
Continuous I.V. administration of hypo-osmolar solutions decreases serum osmolality and leads to excess intracellular fluid volume (water intoxication), whereas continuous I.V. administration of hyperosmolar solutions results in intracellular dehydration, increased serum osmolality and, eventually, ECF volume deficit due to excessive urinary excretion. These states occur because of fluid diffusion and the cell’s attempt to balance the particulate concentrations inside and outside the cell.
REGULATION OF PH
Primarily through the complex chemical regulation of carbonic acid by the lungs and of base bicarbonate by the kidneys, the body maintains the hydrogen ion concentration to keep the ECF pH between 7.35 and 7.45. Nutritional deficiency or excess, disease, injury, or metabolic disturbance can interfere with normal homeostatic mechanisms and raise pH (acidosis) or lower it (alkalosis).
ASSESSING HOMEOSTASIS
The goal of metabolism and homeostasis is to maintain the complex environment of ECF— the plasma—which nourishes and supports every body cell. This special environment is subject to multiple interlocking influences and readily reflects any disturbance in nutrition, chemical or fluid content, and osmotic pressure. Such disturbances can be detected by various laboratory tests. For example, measurements of albumin, prealbumin, and other blood proteins; electrolyte concentration; enzyme and antibody levels; and urine and blood chemistry levels (lipoproteins, glucose, blood urea nitrogen [BUN], creatinine, and creatinine-height index) reflect the state of metabolism, homeostasis, and nutrition
throughout the body. (See Laboratory tests: assessing nutritional status.) Results of such laboratory tests, of course, supplement the information obtained from dietary history and physical examination—which offer gross clinical information about the quality, quantity, and efficiency of metabolic processes. To support clinical information, anthropometry, heightweight ratio, and skin-fold thickness determinations specifically define tissue nutritional status.
throughout the body. (See Laboratory tests: assessing nutritional status.) Results of such laboratory tests, of course, supplement the information obtained from dietary history and physical examination—which offer gross clinical information about the quality, quantity, and efficiency of metabolic processes. To support clinical information, anthropometry, heightweight ratio, and skin-fold thickness determinations specifically define tissue nutritional status.
Laboratory tests: assessing nutritional status
Blood and urine tests provide the most precise data about nutritional status, often revealing nutritional problems before they’re clinically apparent. The list below explains some common tests and what their results mean.
Serum vitamins and minerals
Vitamin and mineral deficiencies commonly screened for include deficiencies in A, B, B12, folic acid, ascorbic acid, beta carotene, riboflavin and, sometimes, zinc, calcium, magnesium, iron, and other minerals.
Serum nutrients
Glucose levels help assess suspected diabetes or hypoglycemia. Glucose may be elevated with stress, acromegaly, Cushing’s syndrome, corticosteroid use, liver disease, sepsis, or overfeeding. Glucose may be decreased with fluid overload, adrenal insufficiency, liver disease, severe sepsis, insulinoma, or pancreatic disorders. Cholesterol and triglyceride levels help differentiate the type of hyperlipoproteinemia.
Nitrogen balance
A negative nitrogen balance indicates inadequate intake of protein or calories.
Hemoglobin and hematocrit
Decreased levels can occur in protein-calorie malnutrition, iron deficiency, overhydration, hemorrhage, and hemolytic disease; elevated levels in dehydration, polycythemia, and folate and vitamin B12 deficiency.
Serum albumin
Reduced levels may indicate overhydration or visceral protein depletion because of GI disease, liver disease, or nephrotic syndrome.
Elevated levels occur in dehydration.
Creatinine-height index (CHI)
This calculated value reflects muscle mass and estimates muscle protein depletion. Reduced CHI may indicate proteincalorie malnutrition or impaired renal function.
Serum prealbumin
This carrier protein for thyroxine is a sensitive indicator of visceral protein.
Total lymphocyte count
This provides an indication of immune status. Counts are low in malnutrition and acquired immunodeficiency syndrome.
The following measures can help you maintain your patient’s homeostasis:
Obtain a complete dietary history and nutritional assessment, including weight history and GI symptoms, to determine if carbohydrate, fat, protein, vitamin, mineral, and water intake are adequate for energy production and for tissue repair and growth. Remember that during periods of rapid tissue synthesis (growth, pregnancy, healing), protein needs increase.
Consult a dietitian about any patient who may be malnourished because of malabsorption syndromes, renal or hepatic disease, or clearliquid diets or who may possibly receive nothing by mouth for more than 5 days. Planned meals that provide adequate carbohydrates, fats, and protein are necessary for convalescence. Supplementary carbohydrates are often needed to spare protein and achieve a positive nitrogen balance.
Accurately record intake and output to assess fluid balance (this includes intake of oral liquids or I.V. solutions and urine, gastric, and stool output).
Weigh the patient daily—at the same time, with the same-type clothing, and on the same scale. Remember, a weight loss of 2.2 lb (1 kg) is equivalent to the loss of 1 L of fluid.
Observe the patient closely for insensible water or unmeasured fluid losses (such as through diaphoresis). Remember, fluid loss from the skin and lungs (normally 900 ml/day) can reach as high as 2,000 ml/day from hyperventilation or tachypnea, thus increasing insensible water losses.
ELDER TIPTeach elderly patients and others vulnerable to fluid imbalances the importance of maintaining adequate fluid intake.
Recognize I.V. solutions that are hypoosmolar, such as 0.45% NaCl (half-normal saline solution). Iso-osmolar solutions include normal saline solution (0.9% NaCl), 5% dextrose in 0.2% NaCl, Ringer’s solutions, and 5% dextrose in water. (The latter acts like a hypotonic solution because dextrose is quickly metabolized, leaving only free water.) Hyperosmolar solutions include 5% dextrose in normal saline solution, 10% dextrose in water, and 5% dextrose in Ringer’s lactate solution.
When continuously administering hypoosmolar solutions, watch for signs of water intoxication: headaches, behavior changes (confusion or disorientation), nausea, vomiting, rising blood pressure, and falling pulse rate.
When continuously administering hyperosmolar solutions, be alert for signs of hypovolemia: thirst, dry mucous membranes, slightly falling blood pressure, rising pulse rate and respirations, low-grade fever (99° F [37.2° C]), and elevated hematocrit, hemoglobin, and BUN levels.
Administer fluid cautiously, especially to the patient with cardiopulmonary or renal disease, and watch for signs of overhydration: constant and irritating cough, dyspnea, moist crackles, rising central venous pressure, and pitting edema (late sign). When the patient is in an upright position, neck and hand vein engorgement is a sign of fluid overload.
ELDER TIPMany older patients take drugs to treat a variety of conditions. Remember that drugs can affect the patient’s nutritional status by altering nutrient absorption, metabolism, utilization, or excretion. Likewise, various foods, beverages, and mineral or vitamin supplements can affect the absorption and effectiveness of drugs. Be aware of these potential interactions when evaluating the patient’s medication regimen and nutritional status.
NUTRITIONAL IMBALANCE
Vitamin A deficiency
A fat-soluble vitamin absorbed in the GI tract, vitamin A maintains epithelial tissue and retinal function. Consequently, deficiency of this vitamin may result in night blindness, decreased color adjustment, keratinization of epithelial tissue, and poor bone growth. Healthy adults have adequate vitamin A reserves to last up to a year; children often don’t.
CAUSES AND INCIDENCE
Vitamin A deficiency usually results from inadequate intake of foods high in vitamin A (liver, kidney, butter, milk, cream, cheese, and fortified margarine) or carotene, a precursor of vitamin A found in dark green leafy vegetables and yellow or orange fruits and vegetables. (Six mg of beta-carotene is equal to 1 mg of vitamin A.) The recommended daily allowance for vitamin A is 3,000 IU for adult males and 2,310 IU for adult females.
Less common causes of vitamin A deficiency include:
malabsorption due to celiac disease, sprue, cirrhosis, obstructive jaundice, cystic fibrosis, giardiasis, or habitual use of mineral oil as a laxative
massive urinary excretion caused by cancer, tuberculosis, pneumonia, nephritis, or urinary tract infection
decreased storage and transport of vitamin A due to hepatic disease.
Each year, more than 80,000 people worldwide—mostly children in underdeveloped countries—lose their sight from severe vitamin A deficiency. This condition is rare in the United States, although many disadvantaged children have substandard levels of vitamin A. With therapy, the chance of reversing symptoms of night blindness and milder conjunctival changes is excellent. When corneal damage is present, emergency treatment is necessary.
COMPLICATION
Corneal damage
SIGNS AND SYMPTOMS
Typically, the first symptom of vitamin A deficiency is night blindness (nyctalopia), which usually becomes apparent when the patient enters a dark place or is caught in the glare of oncoming headlights while driving at night. This condition can progress to xerophthalmia, or drying of the conjunctivas, with development of gray plaques (Bitot’s spots); if unchecked, perforation, scarring, and blindness may result. Keratinization of epithelial tissue causes dry, scaly skin; follicular hyperkeratosis; and shrinking and hardening of the mucous membranes, possibly leading to infections of the eyes and the respiratory or genitourinary tract. An infant with severe vitamin A deficiency shows signs of
failure to thrive and apathy, along with dry skin and corneal changes, which can lead to ulceration and rapid destruction of the cornea.
failure to thrive and apathy, along with dry skin and corneal changes, which can lead to ulceration and rapid destruction of the cornea.
DIAGNOSIS
Dietary history and typical ocular lesions suggest vitamin A deficiency. Carotene levels less than 40 mcg/dl also suggest vitamin A deficiency, but they vary with seasonal ingestion of fruits and vegetables.
CONFIRMING DIAGNOSISA serum level of vitamin A that falls below 10 mcg/dl confirms the diagnosis. Levels between 10 and 19 mcg/dl are also considered low, but the patient isn’t likely to have developed significant symptoms.
TREATMENT
Mild conjunctival changes or night blindness requires vitamin A replacement in the form of cod liver oil or halibut liver oil. Acute deficiency requires aqueous vitamin A solution I.M., or oral tablets, especially when corneal changes have occurred. Therapy for underlying biliary obstruction consists of administration of bile salts; for pancreatic insufficiency, pancreatin, or pancrelipase. Dry skin responds well to creambased or petroleum-based products.
In patients with chronic malabsorption of fat-soluble vitamins, and in those with low dietary intake, prevention of vitamin A deficiency requires aqueous I.V. supplements or an oral water-miscible preparation.
SPECIAL CONSIDERATIONS
Administer oral vitamin A supplements with or after meals or parenterally, as indicated. Watch for signs of hypercarotenemia (orange coloration of the skin and eyes) and hypervitaminosis A (rash, hair loss, anorexia, transient hydrocephalus, and vomiting in children; bone pain, hepatosplenomegaly, diplopia, and irritability in adults). If these signs occur, discontinue supplements and notify the physician immediately. (Hypercarotenemia is relatively harmless; hypervitaminosis A may be toxic.)
Recommended daily allowance of B-complex vitamins | |||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| |||||||||||||||||||||||||||||||||||
PREVENTIONBecause vitamin A deficiency usually results from dietary insufficiency, provide nutritional counseling. Tell the patient that vitamin A comes from animal sources, such as eggs, meat, milk, cheese, cream, liver, kidney, and cod and halibut fish oil, but that healthier choices, such as carrots, pumpkins, sweet potatoes, and most dark green, leafy vegetables are good sources of beta-carotene, vitamin A’s precursor form. Instruct the patient to choose intense-colored fruit or vegetables, which have high beta-carotene content. Provide referrals to appropriate community agencies if necessary.
Vitamin B deficiencies
Vitamin B complex is a group of water-soluble vitamins essential to normal metabolism, cell growth, and blood formation. (See Recommended daily allowance of B-complex vitamins.) The most common deficiencies involve thiamine (B1), riboflavin (B2), niacin (B3), pyridoxine (B6), and cobalamin (B12).
CAUSES AND INCIDENCE
Thiamine deficiency results from malabsorption or inadequate dietary intake of vitamin B1. It also results from alcoholism, prolonged diarrhea, or from increased requirement, which can occur in pregnancy, lactation, and hyperthyroidism. Beriberi, a serious thiamine-deficiency disease, is most prevalent in Asians, who subsist mainly
on diets of unenriched rice and wheat. Although this disease is uncommon in the United States, alcoholics may develop cardiac (wet) beriberi with high-output heart failure, neuropathy, and cerebral disturbances. In times of stress (e.g., pregnancy), malnourished young adults may develop beriberi; infantile beriberi may appear in infants on low-protein diets or in those breastfed by thiamine-deficient mothers.
on diets of unenriched rice and wheat. Although this disease is uncommon in the United States, alcoholics may develop cardiac (wet) beriberi with high-output heart failure, neuropathy, and cerebral disturbances. In times of stress (e.g., pregnancy), malnourished young adults may develop beriberi; infantile beriberi may appear in infants on low-protein diets or in those breastfed by thiamine-deficient mothers.
Riboflavin deficiency (ariboflavinosis) results from a diet deficient in milk, meat, fish, legumes, and green, leafy vegetables. Alcoholism or prolonged diarrhea may also induce riboflavin deficiency. Exposure of milk to sunlight or treatment of legumes with baking soda can destroy riboflavin.
Niacin deficiency, in its advanced form, produces pellagra, which affects the skin, central nervous system (CNS), and GI tract. (See Recognizing pellagra.) Although this deficiency is now seldom found in the United States, it was once common among Southerners who subsisted mainly on corn and consumed minimal animal protein. (Corn is low in niacin and in available tryptophan, the amino acid from which the body synthesizes niacin.) Niacin deficiency is still common in parts of Egypt, Romania, Africa, Serbia, and Montenegro, where corn is the dominant staple food. Niacin deficiency can also occur secondary to carcinoid syndrome or Hartnup disease.
Pyridoxine deficiency usually results from destruction of pyridoxine in infant formulas by autoclaving. A frank deficiency is uncommon in adults, except in patients taking pyridoxine antagonists, such as isoniazid and penicillamine.
Cobalamin deficiency most commonly results from an absence of intrinsic factor in gastric secretions, or an absence of receptor sites after ileal resection. Other causes include malabsorption syndromes associated with sprue, intestinal worm infestation, regional ileitis, and gluten enteropathy, and a diet low in animal protein.
SIGNS AND SYMPTOMS
Thiamine deficiency causes polyneuritis and, possibly, Wernicke’s encephalopathy and Korsakoff’s psychosis. In infants (infantile beriberi), this deficiency produces edema, irritability, abdominal pain, pallor, vomiting, loss of voice and, possibly, seizures. In wet beriberi, severe edema starts in the legs and moves up through the body; dry beriberi causes multiple neurologic symptoms and an emaciated appearance. Thiamine deficiency may also cause cardiomegaly, palpitations, tachycardia, dyspnea, and circulatory collapse. Constipation and indigestion are common; ataxia, nystagmus, and ophthalmoplegia are also possible.
Riboflavin deficiency characteristically causes cheilosis (cracking of the lips and corners of the mouth), sore throat, and glossitis. It may also cause seborrheic dermatitis in the nasolabial folds, scrotum, and vulva and, possibly, generalized dermatitis involving the arms, legs, and trunk. This deficiency can also affect the eyes, producing burning, itching, light sensitivity, tearing, and vascularization of the corneas. Latestage riboflavin deficiency causes neuropathy, mild anemia and, in children, growth retardation.
Niacin deficiency in its early stages produces fatigue, anorexia, muscle weakness, headache, indigestion, mild skin eruptions, weight loss, and backache. In advanced stages (pellagra), it produces dark, scaly dermatitis, especially on exposed body parts, that makes the patient appear to be severely sunburned. The mouth, tongue, and lips become red and sore, which may interfere with eating. Common GI symptoms include nausea, vomiting, and diarrhea. Associated CNS aberrations—confusion, disorientation, and neuritis—may become severe enough to induce hallucinations and paranoia. Because of this triad of symptoms, pellagra is sometimes called
a “3-D” syndrome—dementia, dermatitis, and diarrhea. If not reversed by therapeutic doses of niacin, pellagra can be fatal.
a “3-D” syndrome—dementia, dermatitis, and diarrhea. If not reversed by therapeutic doses of niacin, pellagra can be fatal.
Pyridoxine deficiency in infants causes a wide range of symptoms: dermatitis, occasional cheilosis or glossitis unresponsive to riboflavin therapy, abdominal pain, vomiting, ataxia, and seizures. This deficiency can also lead to CNS disturbances.
Cobalamin deficiency causes pernicious anemia, which produces anorexia, weight loss, abdominal discomfort, constipation, diarrhea, and glossitis; peripheral neuropathy; and, possibly, ataxia, spasticity, and hyperreflexia.
DIAGNOSIS
The following values confirm vitamin B deficiency.
Thiamine deficiency—commonly measured as micrograms per deciliter in a 24-hour urine collection. Deficiency levels are age-related: 1 to 3 years, less than 120; 4 to 6 years, less than 85; 7 to 9 years, less than 70; 10 to 12 years, less than 60; 13 to 15 years, less than 50; adults, less than 27; pregnant women, less than 23 (second trimester), less than 21 (third trimester).
Riboflavin deficiency—measured as micrograms per gram of creatinine in a 24-hour urine collection. Deficiency levels are age-related: 1 to 3 years, less than 150; 4 to 6 years, less than 100; 7 to 9 years, less than 85; 10 to 15 years, less than 70; adults, less than 27; pregnant women, less than 39 (second trimester), less than 30 (third trimester).
Niacin deficiency—measured by N-methyl nicotinamide in a 24-hour urine collection as micrograms per gram of creatinine. Deficiency levels in adults are less than 0.5; in pregnant women, less than 0.5 (first trimester), less than 0.6 (second trimester), and less than 0.8 (third trimester).
Pyridoxine deficiency—xanthurenic acid more than 50 mg/day in 24-hour urine collection after administration of 10 g of L-tryptophan; decreased levels of serum and red blood cell transaminases; reduced excretion of pyridoxic acid in urine.
Cobalamin deficiency—cobalamin serum levels less than 170 pg/ml. Tests to discover the deficiency’s cause include gastric analysis and hemoglobin studies. In addition, the Schilling test measures absorption of radioactive cobalamin with and without intrinsic factor; however, it is rarely used.
TREATMENT
Diet and supplementary vitamins can correct or prevent vitamin B deficiencies, as follows.
Thiamine deficiency—a high-protein diet, with adequate calorie intake, possibly supplemented by B-complex vitamins for early symptoms. Thiamine-rich foods include pork, peas, wheat bran, oatmeal, and liver. Alcoholic beriberi may require thiamine supplements or thiamine hydrochloride as part of a B-complex concentrate.
Riboflavin deficiency—supplemental riboflavin in patients with intractable diarrhea or increased need for riboflavin related to growth, pregnancy, lactation, or wound healing. Good sources of riboflavin are meats, enriched flour, milk and dairy products eggs, cereal, and green, leafy vegetables. Acute riboflavin deficiency requires daily oral doses of riboflavin alone or with other B-complex vitamins. Riboflavin phosphate can also be administered I.V. or I.M.
Niacin deficiency— supplemental B-complex vitamins and dietary enrichment in patients at risk because of marginal diets or alcoholism. Meats, fish, peanuts, brewer’s yeast, enriched breads, and cereals are rich in niacin; milk and eggs, in tryptophan. Confirmed niacin deficiency requires daily doses of niacinamide orally or I.V.
Pyridoxine deficiency—prophylactic pyridoxine therapy in infants and in children with a seizure disorder; supplemental B-complex vitamins in patients with anorexia, malabsorption, or those taking isoniazid or penicillamine. Some women who take hormonal contraceptives may have to supplement their diets with pyridoxine. Confirmed pyridoxine deficiencies require oral or parenteral pyridoxine. Children with seizures stemming from metabolic dysfunction may require daily doses of 200 to 600 mg pyridoxine.
Cobalamin deficiency—parenteral cobalamin in patients with reduced gastric secretion of hydrochloric acid, lack of intrinsic factor, some malabsorption syndromes, or ileum resections. Strict vegetarians may have to supplement their diets with oral vitamin B12. Depending on the deficiency’s severity, supplementary cyanocobalamin or methylcobalamin is usually given parenterally for 5 to 10 days, followed by monthly or daily vitamin B12 supplements.
SPECIAL CONSIDERATIONS
An accurate dietary history provides a baseline for effective dietary counseling.
Identify and observe patients who are at risk for vitamin B deficiencies—alcoholics, the elderly, pregnant women, oral hormonal contraceptive users (vitamins B6 and B12), and people on limited diets.
Administer prescribed supplements. Make sure patients understand how important it is that they adhere strictly to their prescribed treatment for the rest of their lives. Watch
for adverse effects from large doses of niacinamide, such as a flushed sensation or hot flashes, in patients with niacin deficiency. Remember, prolonged intake of niacin can cause hepatic dysfunction. Caution patients with Parkinson’s disease receiving pyridoxine that this drug can impair response to levodopa therapy.
Explain all tests and procedures. Reassure patients that, with treatment, the prognosis is good. Refer patients to appropriate assistance agencies if their diets are inadequate due to adverse socioeconomic conditions.
PREVENTION
Encourage the patient to follow a wellbalanced diet.
Vitamin B12 injections can prevent anemia after surgeries known to cause vitamin B12 deficiency.
Vitamin C deficiency
Vitamin C (ascorbic acid) deficiency leads to scurvy or inadequate production of collagen, an extracellular substance that binds the cells of the teeth, bones, and capillaries. It’s essential for wound healing and burn recovery. Vitamin C is also an important factor in metabolizing such amino acids as tyrosine and phenylalanine. It also acts as a reductant, activating enzymes in the body, as well as converting folic acid into useful components.
Severe vitamin C deficiency results in scurvy, evidenced by hemorrhagic tendencies and abnormal osteoid and dentin formation.
CAUSES AND INCIDENCE
This deficiency’s primary cause is a diet lacking in vitamin C-rich foods, such as citrus fruits, tomatoes, cabbage, broccoli, spinach, and berries. Because the body can’t store this watersoluble vitamin in large amounts, the supply needs to be replenished daily. Other causes include:
destruction of vitamin C in foods by overexposure to air or by overcooking
excessive ingestion of vitamin C during pregnancy, which causes the neonate to require large amounts of the vitamin after birth
marginal intake of vitamin C during periods of physiologic stress—caused by infectious disease, for example—which can deplete tissue saturation of vitamin C
Historically common among sailors and others deprived of fresh fruits and vegetables for long periods of time, vitamin C deficiency is uncommon today in the United States, except in alcoholics, people on restrictedresidue diets, and infants weaned from breast milk to cow’s milk without a vitamin C supplement.
COMPLICATION
Scurvy
SIGNS AND SYMPTOMS
Clinical features of vitamin C deficiency appear as capillaries become increasingly fragile. In an adult, it produces petechiae, ecchymoses, follicular hyperkeratosis (especially on the buttocks and legs), anemia, anorexia, limb and joint pain (especially in the knees), pallor, weakness, swollen or bleeding gums, loose teeth, lethargy, insomnia, poor wound healing, and ocular hemorrhages in the bulbar conjunctivae. (See Scurvy’s effect on gums and legs.) Vitamin C deficiency can also cause beading, fractures of the costochondral junctions of the ribs or epiphysis, and such psychological disturbances as irritability, depression, hysteria, and hypochondriasis.
In a child, vitamin C deficiency produces tender, painful swelling in the legs, causing the child to lie with his legs partially flexed. Other symptoms include fever, diarrhea, and vomiting.
DIAGNOSIS
CONFIRMING DIAGNOSISSerum ascorbic acid levels less than 0.2 mg/dl and white blood cell ascorbic acid levels less than 30 mg/dl help confirm the diagnosis.
Dietary history revealing an inadequate intake of ascorbic acid suggests vitamin C deficiency. A capillary fragility test may be performed on the patient’s forearm with a blood pressure cuff; it’s positive if more than 10 petechiae form after 5 minutes of pressure.
TREATMENT
Because scurvy may be fatal, treatment begins immediately to restore adequate vitamin C intake with daily doses of 100 to 200 mg synthetic vitamin C or orange juice in mild disease and with doses as high as 500 mg/day in severe disease. Symptoms usually subside in 2 to 3 days; hemorrhages and bone disorders, in 2 to 3 weeks.
SPECIAL CONSIDERATIONS
Administer ascorbic acid orally or by slow I.V. infusion, as indicated. Avoid moving the patient unnecessarily to avoid irritating painful joints and muscles. Encourage him to drink orange juice.
Explain the importance of supplemental ascorbic acid. Counsel the patient and his family about good dietary sources of vitamin C.
Advise against taking too much vitamin C. Explain that excessive doses of ascorbic acid may cause nausea, diarrhea, and renal calculi formation and may also interfere with anticoagulant therapy.
PREVENTIONPatients unable or unwilling to consume foods rich in vitamin C or those facing surgery should take daily supplements of ascorbic acid. The recommended daily allowance is 75 to 90 mg/day. Vitamin C supplementation may also prevent this deficiency in recently weaned infants or those drinking formula not fortified with vitamin C.
Vitamin D deficiency
Vitamin D deficiency, commonly called rickets, causes failure of normal bone calcification, which occurs through several mechanisms: decreased calcium and phosphorus (the major components of bone) from the intestines, increased excretion of calcium from renal tubules, and increased parathyroid secretion resulting in increased release of calcium from the bone. The deficiency results in rickets in infants and young children and osteomalacia in adults. With treatment, the prognosis is good. However, in rickets, bone deformities usually persist, whereas in osteomalacia, such deformities may disappear.
CAUSES AND INCIDENCE
Vitamin D deficiency results from inadequate dietary intake of preformed vitamin D, malabsorption of vitamin D, or too little exposure to sunlight.
Once a common childhood disease, rickets is now rare in the United States but occasionally appears in breast-fed infants who don’t receive a vitamin D supplement or in infants receiving a formula with a nonfortified milk base. This deficiency may also occur in overcrowded urban areas in which smog limits sunlight penetration. Incidence is highest in black children who, because of their skin color, absorb less sunlight. (Solar ultraviolet rays irradiate 7-dehydrocholesterol, a precursor of vitamin D, to form calciferol.)
Osteomalacia, also uncommon in the United States, is most prevalent in Asia, among young multiparas who eat a cereal diet and have minimal exposure to sunlight. Other causes include:
vitamin D-resistant rickets (refractory rickets, familial hypophosphatemia) from an inherited impairment of renal tubular reabsorption of phosphate (from vitamin D insensitivity)
conditions that lower absorption of fatsoluble vitamin D, such as chronic pancreatitis, celiac disease, Crohn’s disease, cystic fibrosis, gastric or small-bowel resections, fistulas, colitis, and biliary obstruction
hepatic or renal disease, which interferes with the formation of hydroxylated calciferol, necessary to initiate the formation of a calciumbinding protein in intestinal absorption sites
malfunctioning parathyroid gland (decreased secretion of parathyroid hormone), which contributes to calcium deficiency (normally, vitamin D controls calcium and phosphorus absorption through the intestine) and interferes with activation of vitamin D in the kidneys
COMPLICATIONS
Chronic skeletal pain
Skeletal deformities
Skeletal fractures
SIGNS AND SYMPTOMS
Early indications of vitamin D deficiency are profuse sweating, restlessness, and irritability. Chronic deficiency induces numerous bone malformations due to softening of the bones: bowlegs, knock-knees, rachitic rosary (beading of ends of ribs), enlargement of wrists and ankles, pigeon breast, delayed closing of the fontanels, softening of the skull, and bulging of the forehead. (See Recognizing bowlegs.)
Other rachitic features are poorly developed muscles (potbelly) and infantile tetany. Bone deformities may cause difficulty in walking and in climbing stairs, spontaneous multiple fractures, and lower back and leg pain.
DIAGNOSIS
Physical examination, dietary history, and laboratory tests establish the diagnosis. Test results that suggest vitamin D deficiency include plasma calcium serum levels less than 7.5 mg/dl, serum inorganic phosphorus levels less than 3 mg/dl, serum citrate levels less than 2.5 mg/dl, and alkaline phosphatase levels less than 4 Bodansky units/dl.
CONFIRMING DIAGNOSISX-rays confirm the diagnosis by showing characteristic bone deformities and abnormalities such as Looser’s zones (pseudofractures).
TREATMENT
For osteomalacia and rickets—except when caused by malabsorption—treatment consists of oral doses of vitamin D or sources such as fish, liver, and processed milk. Exposure to sunlight is encouraged. For rickets refractory to vitamin D or in rickets accompanied by hepatic or renal disease, treatment includes 25-hydroxycholecalciferol, 1,25-dihydroxycholecalciferol, or a synthetic analog of active vitamin D. Replacement of deficient calcium and phosphorus also helps to eliminate most symptoms of rickets. Positioning or bracing may be used to reduce or prevent deformities; some skeletal deformities may require corrective surgery.
SPECIAL CONSIDERATIONS
Obtain a dietary history to assess the patient’s current vitamin D intake. Encourage him to eat foods high in vitamin D—fortified milk, fish liver oils, herring, liver, and egg yolks—and get sufficient sun exposure. If deficiency is due to socioeconomic conditions, refer the patient to appropriate community agencies.
If the patient must take vitamin D for a prolonged period, tell him to watch for signs of vitamin D toxicity (headache, nausea, constipation and, after prolonged use, renal calculi).
PREVENTION
Administer supplementary aqueous preparations of vitamin D for chronic fat malabsorption, hydroxylated cholecalciferol for refractory rickets, and supplemental vitamin D for breast-fed infants.
Consider genetic counseling for a patient with a family history of inherited disorders that can cause rickets.
Vitamin E deficiency
Vitamin E (tocopherol) appears to act primarily as an antioxidant, preventing intracellular
oxidation of polyunsaturated fatty acids and other lipids. It protects body tissue from damage caused by unstable substances called free radicals, which can harm cells, tissues, and organs and are believed to be one of the causes of aging’s degenerative process. Vitamin E is also important in the formation of red blood cells (RBCs) and helps the body to use vitamin K. Vitamin E deficiency usually manifests as hemolytic anemia in low-birth-weight or premature neonates. With treatment, prognosis is good.
oxidation of polyunsaturated fatty acids and other lipids. It protects body tissue from damage caused by unstable substances called free radicals, which can harm cells, tissues, and organs and are believed to be one of the causes of aging’s degenerative process. Vitamin E is also important in the formation of red blood cells (RBCs) and helps the body to use vitamin K. Vitamin E deficiency usually manifests as hemolytic anemia in low-birth-weight or premature neonates. With treatment, prognosis is good.
CAUSES AND INCIDENCE
Vitamin E deficiency in infants usually results from consuming formulas high in polyunsaturated fatty acids that are fortified with iron but not vitamin E. Such formulas increase the need for antioxidant vitamin E because the iron supplement catalyzes the oxidation of RBC lipids. A neonate has low tissue concentrations of vitamin E to begin with because only a small amount passes through the placenta; the mother retains most of it. Because vitamin E is a fat-soluble vitamin, deficiency develops in conditions associated with fat malabsorption, such as kwashiorkor, celiac disease, or cystic fibrosis. These conditions may induce megaloblastic or hemolytic anemia and creatinuria, all of which are reversible with vitamin E administration.
Vitamin E deficiency is uncommon in adults but is possible in people whose diets are high in polyunsaturated fatty acids, which increase vitamin E requirements, and in people with vitamin E malabsorption, which impairs RBC survival.
COMPLICATION
Hemolytic anemia
SIGNS AND SYMPTOMS
Vitamin E deficiency is difficult to recognize, but its early symptoms include edema and skin lesions in infants and muscle weakness or intermittent claudication in adults. In premature neonates, vitamin E deficiency produces hemolytic anemia, thrombocythemia, and erythematous papular skin eruption, followed by desquamation.
DIAGNOSIS
CONFIRMING DIAGNOSISDietary and medical histories suggest vitamin E deficiency. Serum alpha-tocopherol levels below 0.5 mg/dl in adults and below 0.2 mg/dl in infants confirm it. Creatinuria, increased creatine kinase levels, hemolytic anemia, and an elevated platelet count generally support the diagnosis.
TREATMENT
Replacement of vitamin E with a water-soluble supplement, either oral or parenteral, is the only appropriate treatment.
SPECIAL CONSIDERATIONS
As indicated, prevent deficiency by providing vitamin E supplements for low-birth-weight neonates receiving formulas not fortified with vitamin E and for adults with vitamin E malabsorption. Many commercial multivitamin supplements are easily absorbed by patients with vitamin E malabsorption.
If vitamin E deficiency is related to socioeconomic conditions, refer the patient to appropriate community agencies.
Inform new mothers who plan to breastfeed that human milk provides adequate vitamin E.
Encourage adult patients to eat foods high in vitamin E; good sources include vegetable oils (corn, safflower, soybean, cottonseed); whole grains; dark green, leafy vegetables; nuts; and legumes. Tell them that heavy consumption of polyunsaturated fatty acids increases the need for vitamin E.
Vitamin K deficiency
Deficiency of vitamin K, an element necessary for formation of prothrombin and other clotting factors in the liver, produces abnormal bleeding. If the deficiency is corrected, the prognosis is excellent.
CAUSES AND INCIDENCE
Vitamin K deficiency is common among neonates in the first few days postpartum due to poor placental transfer of vitamin K and inadequate production of vitamin K-producing intestinal flora. Its other causes include prolonged use of drugs, such as the anticoagulant warfarin and antibiotics that destroy normal intestinal bacteria; decreased flow of bile to the small intestine from obstruction of the bile duct or bile fistula; malabsorption of vitamin K due to sprue, pellagra, bowel resection, ileitis, or ulcerative colitis; chronic hepatic disease, with impaired response of hepatic ribosomes to vitamin K; and cystic fibrosis, with fat malabsorption. Vitamin K deficiency seldom results from insufficient dietary intake of this vitamin.
SIGNS AND SYMPTOMS
DIAGNOSIS
CONFIRMING DIAGNOSISA PT that’s 25% longer than the normal range of 10 to 20 seconds, measured by the Quick method, confirms the diagnosis of vitamin K deficiency after other causes of prolonged PT (such as anticoagulant therapy or hepatic disease) have been ruled out. The International Normalized Ratio (normal value, 0.8 to 1.2) is the more common method of assessing PT adequacy.
Repetition of testing in 24 hours (and regularly during treatment) monitors the therapy’s effectiveness.
TREATMENT
Administration of vitamin K I.V. or I.M. corrects abnormal bleeding tendencies.
SPECIAL CONSIDERATIONS
Administer vitamin K to neonates and patients with fat malabsorption or with prolonged diarrhea from colitis, ileitis, or long-term antibiotic drug therapy.
If the deficiency has a dietary cause, help the patient and his family plan a diet that includes important sources of vitamin K, such as cauliflower, tomatoes, cheese, egg yolks, liver, and green, leafy vegetables.
Warn against self-medication with or overuse of antibiotics, because these drugs destroy the intestinal bacteria needed to generate significant amounts of vitamin K.
Important facts about vitamins A and D
This table illustrates good sources of vitamins A and D, their recommended daily allowances, and the actions they produce.
Vitamin | Sources | Recommended dietary allowance | Action |
Vitamin A | ▪ Carrots; sweet potatoes; dark green, leafy vegetables; butter; margarine; liver; egg yolk | ▪ Ages 1-13: 1,000 to 2,000 international units ▪ Ages ≥ 14: 2,300 to 3,000 international units ▪ Lactating women: 4,000 to 4,300 international units | ▪ Produces retinal pigment and maintains epithelial tissue |
Vitamin D | ▪ Ultraviolet light; fortified foods (especially milk) | ▪ 600 international units daily | ▪ Promotes absorption and regulates metabolism of calcium and phosphorus |
Hypervitaminoses A and D
Hypervitaminosis A is excessive accumulation of vitamin A; hypervitaminosis D, of vitamin D. Although these are toxic conditions, they usually respond well to treatment. They’re most prevalent in infants and children, usually as a result of accidental or misguided overdosage by parents. A related, benign condition called hypercarotenemia results from excessive consumption of carotene, a chemical precursor of vitamin A.
CAUSES AND INCIDENCE
Vitamins A and D are fat-soluble vitamins that accumulate in the body because they aren’t dissolved and excreted in the urine. (See Important facts about vitamins A and D.) In most cases, hypervitaminoses A and D result from ingestion of excessive amounts of supplemental vitamin preparations. A single dose of more than 1 million units of vitamin A can cause acute toxicity; daily doses of 15,000 to 25,000 units taken over weeks or months have proven toxic in infants and children. For the same dose to produce toxicity in adults, ingestion over years is necessary. Doses of 100,000 international units of vitamin D daily for several months can cause toxicity in adults. Individuals who are at risk include those with hyperparathyroidism, kidney disease, sarcoidosis, tuberculosis, or histoplasmosis.
PEDIATRIC TIPIn infants, giving 40,000 international units daily of vitamin D can cause toxicity in 1 to 4 months.
Hypervitaminosis A may occur in patients receiving pharmacologic doses of vitamin A for dermatologic disorders. Hypervitaminosis D may occur in patients receiving high doses of the vitamin as treatment for hypoparathyroidism, rickets, and the osteodystrophy of chronic renal failure, and in infants who consume fortified milk and cereals plus a vitamin supplement. Concentrations of vitamin A in common foods are generally too low to pose a danger of excessive intake. However, hypercarotenemia results from excessive consumption of vegetables high in carotene (a protovitamin that the body converts into vitamin A), such as carrots, sweet potatoes, and dark green, leafy vegetables.
SIGNS AND SYMPTOMS
Chronic hypervitaminosis A produces anorexia, irritability, headache, hair loss, malaise, itching, vertigo, bone pain, bone fragility, and dry, peeling skin. It may also cause hepatosplenomegaly and emotional lability. Acute toxicity may also produce transient hydrocephalus and vomiting. (Hypercarotenemia produces yellow or orange skin coloration.) Hypervitaminosis D causes anorexia, headache, nausea, vomiting, weight loss, polyuria, and polydipsia. Because vitamin D promotes calcium absorption, severe toxicity can lead to hypercalcemia, including calcification of soft tissues, as in the heart, aorta, and renal tubules. Lethargy, confusion, and coma may accompany severe hypercalcemia.
DIAGNOSIS
A thorough patient history suggests hypervitaminosis A.
CONFIRMING DIAGNOSISAn elevated serum vitamin A level (over 90 mcg/dl) confirms hypervitaminosis A.
Patient history and an elevated serum calcium level (over 10.5 mcg/dl) suggest hypervitaminosis D.
CONFIRMING DIAGNOSISAn elevated serum vitamin D level confirms hypervitaminosis D. In children, X-rays showing calcification of tendons, ligaments, and subperiosteal tissues support this diagnosis.
CONFIRMING DIAGNOSISAn elevated serum carotene level (over 250 mcg/dl) confirms hypercarotenemia.
TREATMENT
Withholding vitamin supplements usually corrects hypervitaminosis A quickly and hypervitaminosis D gradually. Hypercalcemia may persist for weeks or months after the patient stops taking vitamin D. Treatment for severe hypervitaminosis D may include glucocorticoids to control hypercalcemia and prevent renal damage. In the acute stage, diuretics or other emergency measures for severe hypercalcemia may be necessary. Hypercarotenemia responds well to a diet free of high-carotene foods.
SPECIAL CONSIDERATIONS
Keep the patient comfortable, and reassure him that symptoms will subside after he stops taking the vitamin.
Make sure the patient or the parents of a child with these conditions understand that vitamins aren’t innocuous. Explain the hazards associated with excessive vitamin intake. Point out that vitamin A and D requirements can easily be met with a diet containing dark green, leafy vegetables; fruits; and fortified milk or milk products.
PREVENTIONMonitor serum vitamin A lev els in patients receiving doses above the recommended daily allowance and serum calcium levels in patients receiving pharmacologic doses of vitamin D.
Iodine deficiency
Iodine deficiency is the absence of sufficient levels of iodine to satisfy daily metabolic requirements. Because the thyroid gland uses most of the body’s iodine stores, iodine deficiency is apt to cause hypothyroidism and thyroid gland hypertrophy (endemic goiter). Other effects of deficiency range from dental caries to cretinism in neonates born to iodine-deficient mothers. Iodine deficiency is most common in pregnant or lactating women due to their exaggerated metabolic need for this element. Iodine deficiency responds readily to treatment with iodine supplements.
CAUSES AND INCIDENCE
Iodine deficiency usually results from insufficient intake of dietary sources of iodine, such as iodized table salt, seafood, and dark green, leafy vegetables. (Normal iodine requirements range from 35 mcg/day for infants to 150 mcg/day for lactating women; the average adult needs 1 mcg/kg of body weight.) Iodine deficiency may also result from an increase in metabolic demands during pregnancy, lactation, and adolescence.
COMPLICATIONS
Hypothyroidism
Goiter
SIGNS AND SYMPTOMS
Clinical features of iodine deficiency depend on the degree of hypothyroidism that develops (in addition to the development of a goiter). Mild deficiency may produce only mild, nonspecific symptoms, such as lassitude, fatigue, and loss of motivation. Severe deficiency usually generates the typically overt and unmistakable features of hypothyroidism: bradycardia; decreased pulse pressure and cardiac output; weakness; hoarseness; dry, flaky, inelastic skin; puffy face; thick tongue; delayed relaxation phase in deep tendon reflexes; poor memory; hearing loss; chills; anorexia; and nystagmus. In women, iodine deficiency may also cause menorrhagia and amenorrhea.
Cretinism—hypothyroidism that develops in utero or in early infancy—is characterized by failure to thrive, neonatal jaundice, and hypothermia. By age 3 to 6 months, the infant may display spastic diplegia and signs and symptoms similar to those seen in infants with Down syndrome.
DIAGNOSIS
CONFIRMING DIAGNOSISAbnormal laboratory test results include low thyroxine (T4) levels with high radioactive iodine (131I) uptake, low 24-hour urine iodine levels, and high thyroidstimulating hormone levels. Radioiodine uptake test traces131I in the thyroid 24 hours after administration; triiodothyronine-resin or T4-resin uptake test shows values 25% below normal.
TREATMENT
Severe iodine deficiency requires administration of iodine supplements (potassium iodide [SSKI]). Mild deficiency may be corrected by increasing iodine intake through the use of iodized table salt and consumption of iodine-rich foods (seafood and green, leafy vegetables).
SPECIAL CONSIDERATIONS
Administer SSKI preparation in milk or juice to reduce gastric irritation and mask its metallic taste. To prevent tooth discoloration, tell the patient to drink the solution through a straw. Store the solution in a light-resistant container.
PREVENTIONRecommend the use of iodized salt and consumption of iodine-rich foods for high-risk patients—especially adolescents and pregnant or lactating women.
Advise pregnant women that severe iodine deficiency may produce cretinism in neonates, and instruct them to watch for early signs of iodine deficiency, such as fatigue, lassitude, weakness, and decreased mental function.
Zinc deficiency
Zinc, an essential trace element that’s present in the bones, teeth, hair, skin, testes, liver, and muscles, is also a vital component of many enzymes. Zinc promotes synthesis of deoxyribonucleic acid, ribonucleic acid and, ultimately, protein, and maintains normal blood concentrations of vitamin A by mobilizing it from the liver. The prognosis is good with correction of the deficiency.
CAUSES AND INCIDENCE
Zinc deficiency usually results from excessive intake of foods (containing iron, calcium, vitamin D, and the fiber and phytates in cereals) that bind zinc to form insoluble chelates that prevent its absorption. Occasionally, it results from blood loss due to parasitism and low intake of foods containing zinc. Alcohol and corticosteroids increase renal excretion of zinc.
Zinc deficiency is most common in people from underdeveloped countries, especially in the Middle East. Children are most susceptible to this deficiency during periods of rapid growth.
SIGNS AND SYMPTOMS
Zinc deficiency produces hepatosplenomegaly, sparse hair growth, soft and misshapen nails, poor wound healing, anorexia, hypogeusesthesia (decreased taste acuity), dysgeusia (unpleasant taste), hyposmia (decreased odor acuity), dysosmia (unpleasant odor in nasopharynx), severe iron deficiency anemia, bone deformities and, when chronic, hypogonadism, dwarfism, and hyperpigmentation.
DIAGNOSIS
CONFIRMING DIAGNOSISFasting serum zinc levels below 70 mcg/dl confirm zinc deficiency and indicate altered phosphate metabolism, imbalance between aerobic and anaerobic metabolism, and decreased pancreatic enzyme levels.
TREATMENT
Treatment consists of correcting the deficiency’s underlying cause and administering zinc supplements, as necessary.
SPECIAL CONSIDERATIONS
Advise the patient to take zinc supplements with milk or meals to prevent gastric distress and vomiting.
PREVENTIONEncourage a balanced diet that includes seafood, oatmeal, bran, meat, eggs, nuts, and dry yeast and the correct use of calcium andiron supplements.
Obesity
Obesity is an excess of body fat, generally 20% above ideal body weight. The prognosis for correction of obesity is poor: Fewer than 30% of patients succeed in losing 20 lb (9 kg), and only half of these maintain the loss over a prolonged period.
CAUSES AND INCIDENCE
Obesity results from excessive calorie intake and inadequate expenditure of energy. Theories to explain this condition include hypothalamic dysfunction of hunger and satiety centers, genetic predisposition, abnormal absorption of nutrients, and impaired action of GI and growth hormones and of hormonal regulators such as insulin. An inverse relationship between socioeconomic status and the prevalence of obesity has been documented, especially in women. Obesity in parents increases the probability of obesity in children, from genetic or environmental factors, such as activity levels and learned patterns of eating. Psychological factors, such as stress or emotional eating, may also contribute to obesity. Rates of obesity are climbing, and the percentage of children and adolescents who are obese has doubled in the past 20 years.
COMPLICATIONS
Respiratory difficulties
Hypertension
Cardiovascular disease
Diabetes mellitus
Renal disease
Gallbladder disease
Psychosocial difficulties
Premature death
DIAGNOSTIC AIDS
Weight categories, overweight and obesity, are determined by using a person’s height and weight to calculate the body mass index (BMI). Overweight is defined as a BMI between 25.0 and 29.9. Obesity is defined as a BMI of 30 or higher. Measurement of the thickness of subcutaneous fat folds with calipers provides an approximation of total body fat. Although this measurement is reliable and isn’t subject to daily fluctuations, it has little meaning for the patient in monitoring subsequent weight loss.
TREATMENT
Successful management of obesity must decrease the patient’s daily calorie intake while increasing his activity level. Effective treatment must be based on a balanced, low-calorie diet that eliminates foods high in fat or sugar. Lifelong maintenance of these improved eating and exercise patterns is necessary to achieve long-term benefits.
The popular low-carbohydrate diets offer no long-term advantage; rapid early weight reduction is due to loss of water, not fat. These and other crash or fad diets have the overwhelming drawback that they don’t teach the patient long-term modification of eating patterns and often lead to the “yo-yo syndrome”—episodes of repeated weight loss followed by weight gain. This can be more detrimental than the obesity itself because of the severe stress it can place on the body.
Total fasting is an effective method of rapid weight reduction but requires close monitoring and supervision to minimize risks of ketonemia, electrolyte imbalance, hypotension, and loss of lean body mass. Prolonged fasting and verylow-calorie diets have been associated with sudden death, possibly resulting from cardiac arrhythmias caused by electrolyte abnormalities. These methods also neglect patient re-education, which is necessary for long-term weight maintenance. The best way to lose weight is to do so slowly, losing 1 to 2 pounds per week.
Treatment may also include behavior modification techniques, which promote fundamental changes in eating habits and activity patterns.
Orlistat and its over-the-counter version, Alli, are FDA-approved drug therapies for weight loss. These drugs promote weight loss by decreasing the absorption of dietary fat. They need to be combined with healthy eating and physical activity to be most effective.
Obesity may be treated surgically with restriction or malabsorptive procedures. Those with a BMI greater than 40 or with a BMI between 35 and 39.9 along with a weight-related health problem may qualify for weight-loss surgery. Vertical banded gastroplasty, gastric banding, and the sleeve procedure represent restrictive surgical procedures that aid in weight loss by decreasing the volume of food that the stomach can accommodate. Gastric bypass with a Rouxen-Y procedure produces weight loss by both restricting stomach capacity and inducing malabsorption; food is rerouted to bypass part of the
small intestine. Nutrition counseling before and after these procedures is recommended to enhance safe weight loss, educate the patient about proper diet advancement, and monitor for nutritional deficiencies. Psychological and social support are also beneficial before and after surgery.
small intestine. Nutrition counseling before and after these procedures is recommended to enhance safe weight loss, educate the patient about proper diet advancement, and monitor for nutritional deficiencies. Psychological and social support are also beneficial before and after surgery.
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
