# Nutrient Requirements

Nutrient Requirements is a topic covered in the Washington Manual of Medical Therapeutics.

To view the entire topic, please or .

The Washington Manual is an award-winning, complete mobile solution for nurses and students. Look up information on diseases, tests, and procedures; then consult the database with 5,000+ drugs or refer to 65,000+ dictionary terms. Explore these free sample topics:

-- The first section of this topic is shown below --

## Energy

• Total daily energy expenditure (TEE) is composed of resting energy expenditure (normally ∼70% of TEE), the thermic effect of food (normally ∼10% of TEE), and energy expenditure of physical activity (normally ∼20% of TEE).
• Use of predictive equations can provide a reasonable estimate of daily energy requirements that should be modified based on the factors that affect the patient’s metabolic rate.
• Malnutrition and hypocaloric feeding may decrease resting energy expenditure to 15%–20% below expected for actual body size, whereas metabolic stressors, such as inflammatory diseases or trauma, often increase energy requirements by ∼30%–50%.
• The Harris–Benedict equation provides a reasonable estimate of resting energy expenditure (in kilocalories [kcal] per day) in healthy adults. It takes into account the effects of body size and lean tissue mass (which are influenced by gender and age) on energy requirements and can be used to estimate total daily energy needs in hospitalized patients (where W is the weight in kilograms, H the height in centimeters, and A is the age in years).1
• Men = 66 + (13.7 × W ) + (5 × H ) − (6.8 × A)
• Women = 665 + (9.6 × W ) + (1.8 × H ) − (4.7 × A)
• Energy requirements per kilogram of body weight are inversely related to body mass index (BMI) (Table 2-1). The lower range within each category should be considered in insulin-resistant, critically ill patients unless they are depleted in body fat.
• Ideal body weight can be estimated based on height
• For men: 106 + 6 lb for each inch over 5 ft
• For women, 100 + 5 lb for each inch over 5 ft
Table 2-1: Estimated Energy Requirements for Hospitalized Patients Based on Body Mass Index
 Body Mass Index (kg/m2) Energy Requirements (kcal/kg/d) 15 35–40 15–19 30–35 20–24 20–25 25–29 15–20 ≥30 <15

Note: These values are recommended for critically ill patients and all obese patients; add 20% of total calories in estimating energy requirements in non–critically ill patients.

## Protein

• Protein intake of 0.8 g/kg/d meets the requirements of 97% of the adult population.
• Protein requirements are affected by several factors, including the amount of nonprotein calories provided, overall energy requirements, protein quality, baseline nutritional status, and the presence of inflammation and metabolic stressors (Table 2-2).
• Inadequate amounts of any essential amino acid results in inefficient utilization.
• Illness increases the efflux of amino acids from skeletal muscle; however, increasing protein intake to >1.2 g/kg/d of prehospitalization body weight in critically ill patients may not reduce the loss of lean body mass.2
Table 2-2: Recommended Daily Protein Intake
 Clinical Condition Protein Requirements (g/kg IBW/d)a Normal 0.8 Metabolic stress (illness/injury) 1.0–1.5 Acute renal failure (undialyzed) 0.8–1.0 Hemodialysis 1.2–1.4 Peritoneal dialysis 1.3–1.5

IBW, ideal body weight.

aAdditional protein intake may be needed to compensate for excess protein loss in specific patient populations such as those with burn injury, open wounds, and protein-losing enteropathy or nephropathy. Lower protein intake may be necessary in patients with chronic renal insufficiency who are not treated by dialysis and certain patients with hepatic encephalopathy.

## Essential Fatty Acids

• Humans lack the desaturase enzyme needed to produce the ω-3 and ω-6 fatty acids. Therefore, linoleic acid should constitute at least 2% and linolenic acid at least 0.5% of the daily caloric intake to prevent deficiency.
• The plasma pattern of increased triene-to-tetraene ratio (>0.4) can be used to detect essential fatty acid deficiency.

## Carbohydrate

Certain tissues, such as bone marrow, erythrocytes, leukocytes, renal medulla, eye tissues, and peripheral nerves, cannot metabolize fatty acids and require glucose (∼40 g/d) as a fuel. Endogenous protein and glycerol from lipid stores can undergo gluconeogenesis to supply glucose-requiring organs.

## Major Minerals

Major minerals such as sodium, potassium, and chloride are important for ionic equilibrium, water balance, and normal cell function.

## Micronutrients (Trace Elements and Vitamins)

Trace elements and vitamins are essential constituents of enzyme complexes. The recommended dietary intake for trace elements, fat-soluble vitamins, and water-soluble vitamins is set at two standard deviations above the estimated mean as to meet the needs of 97% of the healthy population.

See Table 2-3 for specifics regarding the assessment of micronutrient nutritional states as well as signs and symptoms of micronutrient deficiency and toxicity.

Table 2-3: Trace Minerals, Fat-Soluble Vitamins, and Water-Soluble Vitamins: Recommended Daily Intake, Deficiency, At-Risk Populations, Toxicity, and Status Evaluation
 Nutrient Recommended Daily Enteral Intake3/Parenteral Intake4 Signs and Symptoms of Deficiency5,6,7,8,9,10,11,12,13,14,15,16 Populations at Risk for Deficiency Signs and Symptoms of Toxicity Status Evaluation3,17 Chromium (Cr3+) 30–35 μg/10–15 μg Glucose intolerance, peripheral neuropathya Nonea,5 PO: gastritisIV: skin irritationCr6+: (steel, welding) lung carcinogen if inhaled Chromiums Copper (Cu2+) 900 μg/300–500 μg Hypochromic normocytic or macrocytic anemia (rarely microcytic), neutropenia, thrombocytopenia, diarrhea, osteoporosis/pathologic fracturesaIntrinsic: Menkes disease18 Chronic diarrhea, high-zinc/low-protein diets17,19 PO: gastritis, nausea, vomiting, coma, movement/neurologic abnormalities, hepatic necrosisIntrinsic: Wilson disease Coppers,uCeruloplasminp Iodine (I−) 150 μg/70–140 μg (not routinely added) Thyroid hyperplasia (goiter) + functional hypothyroidismIntrinsic in utero: cretinism, poor CNS development, hypothyroidism Those without access to fortified salt, grain, milk, or cooking oil20 Deficiency: causes hypothyroidismExcess: acutely causes hypothyroidism; chronic excess: hyperthyroidism TSHs, iodineu (24-h intake and iodine: Cr ratio are more representative than a single sample)Thyroglobulins6,20 Iron (Fe2+,3+) 8 mg/1.0–1.5 μg (not routinely added) Fatigue, hypochromic microcytic anemia, glossitis, koilonychia Reproductive-age females, pregnant females, chronic anemias, hemoglobinopathies, post–gastric bypass/duodenectomy, alcoholics PO or IV: hemosiderosis, followed by deposition in liver, pancreas, heart, and glandsIntrinsic: hereditary hemochromatosis Ferritins, TIBCs, % transferrin saturationc, irons Manganese (Mn2+) 2.3 mg/60–100 μg Hypercholesterolemia, dermatitis, dementia, weight lossb Chronic liver disease, iron-deficient populations PO: nonebInhalation: hallucination, Parkinsonian-type symptoms21 No reliable markersManganeses does not reflect bodily stores, especially in the CNS Selenium 55 μg/20–60 μg Myalgias, cardiomyopathyaIntrinsic: Keshan disease (Chinese children), Kashin–Beck disease, myxedematous endemic cretinism22 Endemic areas of low soil content include certain parts of China and |New Zealand10 PO: nausea, diarrhea, AMS, irritability, fatigue, peripheral neuropathy, hair loss, white splotchy nails, halitosis (garlic-like odor) Seleniums, glutathione peroxidase activityb Zinc (Zn2+) 11 mg/2.5–5.0 mg Poor wound healing, diarrhea (high fistula risk), dysgeusia, teratogenicity, hypogonadism, infertility, acrofacial and oral skin lesions (glossitis, alopecia), behavioral changesIntrinsic: acrodermatitis enteropathica Chronic diarrhea, cereal-based diets, alcoholics, chronic liver disease, sickle cell, HIV, pancreatic insufficiency/any intestinal malabsorptive states, fistulas/ostomies, nephrotic syndrome, diabetes, post–gastric bypass/duodenectomy, anorexia, pregnancy19Intrinsic: acrodermatitis enteropathica PO: nausea, vomiting, gastritis, diarrhea, low HDL, gastric erosionsCompetition with GI absorption can precipitate Cu2+ deficiencyInhaled: hyperpnea, weakness, diaphoresis Zincs,p, alkaline phosphatases (good for those on TPN, but in general Zincs,p hair, RBC, WBC levels can be misleading)Zinc radioisotope studies (most accurate tests at present; limited by cost and availability)7 Vitamin ARetinol 900 μg/3300 IU Conjunctival xerosis, keratomalacia, follicular hyperkeratosis, night blindness, Bitot spots, corneal + retinal dysfunction Any malabsorptive state involving proximal small bowel, vegetarians, chronic liver disease Acute: teratogenic, skin exfoliation, intracranial hypertension, hepatocellular necrosisChronic: alopecia, ataxia, cheilitis, dermatitis, conjunctivitis, pseudotumor cerebri, hyperlipidemia, hyperostosis Retinols, retinol estersp, electroretinogram, liver biopsy (diagnostic for toxicity), retinol binding protein (useful in ESRD; accurately assesses blood levels)23 Vitamin DErgocalciferol 5–15 μg/200 IU Rickets/osteomalacia Any malabsorptive state involving proximal small bowel, chronic liver diseaseOf note: those with higher skin melanin content (i.e., darker skin) have low baseline 25-OH vitamin D levels; it is unclear whether this merits their inclusion as an “at-risk” population23 Hypercalcemia, hyperphosphatemia, which can lead to CaPO4 precipitation, systemic calcification +/− AMS +/− AKI 25-OH vitamin DsOf note: lively debate between IOM and Endocrine Society regarding definitions of deficiency, goal serum 25-OH levels, and at-risk populations24,25 Vitamin E(α,γ)-Tocopherol 15 mg/10 IU Hemolytic anemia, posterior column degeneration, ophthalmoplegia, peripheral neuropathySeen in severe malabsorption, abetalipoproteinemia Any malabsorptive state involving proximal small bowel, chronic liver disease Possible increased risk in hemorrhagic CVA, functional inhibition of vitamin K–mediated procoagulants TocopherolMust account for cholesterol/triglyceride ratio: otherwise, higher cholesterol/triglyceride ratio overestimates vitamin E, lower cholesterol/triglyceride ratio underestimates vitamin E16,c Vitamin KPhylloquinone 120 μg/150 IU Hemorrhagic disease of newborn, coagulopathy Any malabsorptive state involving proximal small bowel, chronic liver disease In utero: hemolytic anemia, hyperbilirubinemia, kernicterusIV: flushing, dyspnea, hypotension (possibly related to dispersal agent) Prothrombin timep Vitamin B1Thiamine 1.2 mg/6 mg Irritability, fatigue, headacheWernicke encephalopathy, Korsakoff psychosis, “wet” beriberi, “dry” beriberi Alcoholics, severely malnourished IV: lethargy and ataxia RBC transketolase activityb, thiamineb,u Vitamin B2Riboflavin 1.3 mg/3.6 mg Cheilosis, angular stomatitis, glossitis, seborrheic dermatitis, normocytic normochromic anemia Alcoholics, severely malnourished Noneb RBC glutathione reductase activityp Vitamin B3Niacin 16 mg/40 mg Pellagra dysesthesias, glossitis, stomatitis, vaginitis, vertigoIntrinsic: Hartnup disease Alcoholics, malignant carcinoid syndrome, severely malnourished Flushing, hyperglycemia, hyperuricemia, hepatocellular injuryb N-methyl-nicotinamideu Vitamin B5Pantothenic acid 5 mg/15 mg Fatigue, abdominal pain, vomiting, insomnia, paresthesiasb Alcoholics3 PO: diarrhea Pantothenic acidu Vitamin B6Pyridoxine 1.3–1.7 mg/6 mg Cheilosis, stomatitis, glossitis, irritability, depression, confusion, normochromic normocytic anemia Alcoholics, diabetics, celiac sprue, chronic isoniazid or penicillamine use15 Peripheral neuropathy, photosensitivity Pyridoxal phosphatep Vitamin B7Biotin 30 μg/60 μg Mental status changes, myalgias, hyperesthesias, anorexiac,26 (excessive egg white consumption results in avidin-mediated biotin inactivation) Alcoholics Noneb,26 Biotinp, methyl-citrateu, 3-methyl- crotonyglycineu, 3-hydroxyisovalerateu Vitamin B9Folic acid 400 μg/600 μg Bone marrow suppression, macrocytic megaloblastic anemia, glossitis, diarrheaCan be precipitated by sulfasalazine + phenytoin Alcoholics, celiac or tropical sprue, chronic sulfasalazine use PO: may lower seizure threshold in those taking anticonvulsants Folic acids, RBC folic acidp Vitamin B12Cobalamin 2.4 μg/5 μg Bone marrow suppression, macrocytic megaloblastic anemia, glossitis, diarrhea, posterolateral column demyelination, AMS, depression, psychosis Vegetarians, atrophic gastritis, pernicious anemia, celiac sprue, Crohn disease, patients postgastrectomy or ileal resection Noneb Cobalamin (B12)s, methylmalonic acids,p Vitamin CAscorbic acid 90 mg/200 mg Scurvy, ossification abnormalitiesTobacco lowers plasma and WBC vitamin C13Sudden cessation of high-dose vitamin C can precipitate scurvy Fruit-deficient diet, smokers,13ESRD27 Nausea, diarrhea, increased oxalate synthesis (theoretical nephrolithiasis risk) Ascorbic acidp, leukocyte ascorbic acid

AKI, acute kidney injury; AMS, altered mental status; CNS, central nervous system; CVA, cerebrovascular accident; ESRD, end-stage renal disease; IOM, Institute of Medicine; GI, gastrointestinal; HDL, high-density lipoprotein (cholesterol); RBC, red blood cell; TIBC, total iron bonding capacity; TPN, total parenteral nutrition; TSH, thyroid-stimulating hormone; WBC, white blood cell.

Subscript: b, blood; c, calculated; p, plasma; s, serum; u, urine.

aOnly reported in patients on long-term TPN.

bNever demonstrated in humans.

cOnly able to induce under experimental conditions and/or only been able to induce in animals.

## Special Considerations

• Both the amount and location of prior gut resection influence nutrient needs. Patients with a reduced length of functional small bowel may require additional vitamins and minerals if they are not receiving parenteral nutrition. Table 2-4 provides guidelines for supplementation in these patients.
• Ileal inflammation, resection, inflammatory bowel disease (IBD), and bypass (ileojejunal bypass) can cause B12 deficiency and bile salt loss. Diarrhea in this setting may be improved with oral cholestyramine.
• Proximal gut resection (stomach or duodenum) via partial gastrectomy, Billroth I and II, duodenal switch/biliopancreatic diversion, Roux-en-Y gastric bypass, pancreaticoduodenectomy (Whipple), and sleeve gastrectomy may impair absorption of divalent cations such as iron, calcium, and copper. Copper deficiency is extremely common in post–gastric bypass patients who do not receive routine supplementation.28
• Patients with excessive gastrointestinal (GI) tract losses require additional fluids and electrolytes. An assessment of fluid losses due to diarrhea, ostomy output, and fistula volume should be made to help determine fluid requirements. Intestinal mineral losses may be calculated by multiplying the volume of fluid loss by the fluid electrolyte concentration (Table 2-5).
• Hyperammonemic encephalopathy is an uncommon but serious complication of Roux-en-Y gastric bypass with an estimated mortality rate of 50%.29 Laboratory hallmarks include elevated ammonia, elevated plasma glutamate, hypoalbuminemia, nutritional and essential amino acid deficiencies, and low zinc.30 It does not appear to resolve with replacement of trace elements. Some reports suggest improvement with total parental nutrition after several months; however, data remain limited.31
Table 2-4: Guidelines for Vitamin and Mineral Supplementation in Patients with Severe Malabsorption
 Supplement Dose Route Prenatal multivitamin with mineralsa 1 tablet daily PO Vitamin Da 50,000 units 2–3 times per week PO Calciuma 500 mg elemental calcium tid–qid PO Vitamin B12b 1 mg daily PO – 100–500 μg q1–2 mo SC Vitamin Ab 10,000–50,000 units daily PO Vitamin Kb 5 mg/d PO – 5–10 mg/wk SC Vitamin Eb 30 units/d PO Magnesium gluconateb 108–169 mg elemental magnesium qid PO Magnesium sulfateb 290 mg elemental magnesium 1–3 times per week IM/IV Zinc gluconate or zinc sulfateb 25 mg elemental zinc daily plus 100 mg elemental zinc per liter intestinal output PO Ferrous sulfateb 60 mg elemental iron tid PO Iron dextranb Daily dose based on formula or table IV

aRecommended routinely for all patients.

bRecommended for patients with documented nutrient deficiency or malabsorption.

Table 2-5: Electrolyte Concentrations in Gastrointestinal Fluids
 Location Na (mEq/L) K (mEq/L) Cl (mEq/L) HCO3 (mEq/L) Stomach 65 10 100 – Bile 150 4 100 35 Pancreas 150 7 80 75 Duodenum 90 15 90 15 Mid–small bowel 140 6 100 20 Terminal ileum 140 8 60 70 Rectum 40 90 15 30

-- To view the remaining sections of this topic, please or --

## Energy

• Total daily energy expenditure (TEE) is composed of resting energy expenditure (normally ∼70% of TEE), the thermic effect of food (normally ∼10% of TEE), and energy expenditure of physical activity (normally ∼20% of TEE).
• Use of predictive equations can provide a reasonable estimate of daily energy requirements that should be modified based on the factors that affect the patient’s metabolic rate.
• Malnutrition and hypocaloric feeding may decrease resting energy expenditure to 15%–20% below expected for actual body size, whereas metabolic stressors, such as inflammatory diseases or trauma, often increase energy requirements by ∼30%–50%.
• The Harris–Benedict equation provides a reasonable estimate of resting energy expenditure (in kilocalories [kcal] per day) in healthy adults. It takes into account the effects of body size and lean tissue mass (which are influenced by gender and age) on energy requirements and can be used to estimate total daily energy needs in hospitalized patients (where W is the weight in kilograms, H the height in centimeters, and A is the age in years).1
• Men = 66 + (13.7 × W ) + (5 × H ) − (6.8 × A)
• Women = 665 + (9.6 × W ) + (1.8 × H ) − (4.7 × A)
• Energy requirements per kilogram of body weight are inversely related to body mass index (BMI) (Table 2-1). The lower range within each category should be considered in insulin-resistant, critically ill patients unless they are depleted in body fat.
• Ideal body weight can be estimated based on height
• For men: 106 + 6 lb for each inch over 5 ft
• For women, 100 + 5 lb for each inch over 5 ft
Table 2-1: Estimated Energy Requirements for Hospitalized Patients Based on Body Mass Index
 Body Mass Index (kg/m2) Energy Requirements (kcal/kg/d) 15 35–40 15–19 30–35 20–24 20–25 25–29 15–20 ≥30 <15

Note: These values are recommended for critically ill patients and all obese patients; add 20% of total calories in estimating energy requirements in non–critically ill patients.

## Protein

• Protein intake of 0.8 g/kg/d meets the requirements of 97% of the adult population.
• Protein requirements are affected by several factors, including the amount of nonprotein calories provided, overall energy requirements, protein quality, baseline nutritional status, and the presence of inflammation and metabolic stressors (Table 2-2).
• Inadequate amounts of any essential amino acid results in inefficient utilization.
• Illness increases the efflux of amino acids from skeletal muscle; however, increasing protein intake to >1.2 g/kg/d of prehospitalization body weight in critically ill patients may not reduce the loss of lean body mass.2
Table 2-2: Recommended Daily Protein Intake
 Clinical Condition Protein Requirements (g/kg IBW/d)a Normal 0.8 Metabolic stress (illness/injury) 1.0–1.5 Acute renal failure (undialyzed) 0.8–1.0 Hemodialysis 1.2–1.4 Peritoneal dialysis 1.3–1.5

IBW, ideal body weight.

aAdditional protein intake may be needed to compensate for excess protein loss in specific patient populations such as those with burn injury, open wounds, and protein-losing enteropathy or nephropathy. Lower protein intake may be necessary in patients with chronic renal insufficiency who are not treated by dialysis and certain patients with hepatic encephalopathy.

## Essential Fatty Acids

• Humans lack the desaturase enzyme needed to produce the ω-3 and ω-6 fatty acids. Therefore, linoleic acid should constitute at least 2% and linolenic acid at least 0.5% of the daily caloric intake to prevent deficiency.
• The plasma pattern of increased triene-to-tetraene ratio (>0.4) can be used to detect essential fatty acid deficiency.

## Carbohydrate

Certain tissues, such as bone marrow, erythrocytes, leukocytes, renal medulla, eye tissues, and peripheral nerves, cannot metabolize fatty acids and require glucose (∼40 g/d) as a fuel. Endogenous protein and glycerol from lipid stores can undergo gluconeogenesis to supply glucose-requiring organs.

## Major Minerals

Major minerals such as sodium, potassium, and chloride are important for ionic equilibrium, water balance, and normal cell function.

## Micronutrients (Trace Elements and Vitamins)

Trace elements and vitamins are essential constituents of enzyme complexes. The recommended dietary intake for trace elements, fat-soluble vitamins, and water-soluble vitamins is set at two standard deviations above the estimated mean as to meet the needs of 97% of the healthy population.

See Table 2-3 for specifics regarding the assessment of micronutrient nutritional states as well as signs and symptoms of micronutrient deficiency and toxicity.

Table 2-3: Trace Minerals, Fat-Soluble Vitamins, and Water-Soluble Vitamins: Recommended Daily Intake, Deficiency, At-Risk Populations, Toxicity, and Status Evaluation
 Nutrient Recommended Daily Enteral Intake3/Parenteral Intake4 Signs and Symptoms of Deficiency5,6,7,8,9,10,11,12,13,14,15,16 Populations at Risk for Deficiency Signs and Symptoms of Toxicity Status Evaluation3,17 Chromium (Cr3+) 30–35 μg/10–15 μg Glucose intolerance, peripheral neuropathya Nonea,5 PO: gastritisIV: skin irritationCr6+: (steel, welding) lung carcinogen if inhaled Chromiums Copper (Cu2+) 900 μg/300–500 μg Hypochromic normocytic or macrocytic anemia (rarely microcytic), neutropenia, thrombocytopenia, diarrhea, osteoporosis/pathologic fracturesaIntrinsic: Menkes disease18 Chronic diarrhea, high-zinc/low-protein diets17,19 PO: gastritis, nausea, vomiting, coma, movement/neurologic abnormalities, hepatic necrosisIntrinsic: Wilson disease Coppers,uCeruloplasminp Iodine (I−) 150 μg/70–140 μg (not routinely added) Thyroid hyperplasia (goiter) + functional hypothyroidismIntrinsic in utero: cretinism, poor CNS development, hypothyroidism Those without access to fortified salt, grain, milk, or cooking oil20 Deficiency: causes hypothyroidismExcess: acutely causes hypothyroidism; chronic excess: hyperthyroidism TSHs, iodineu (24-h intake and iodine: Cr ratio are more representative than a single sample)Thyroglobulins6,20 Iron (Fe2+,3+) 8 mg/1.0–1.5 μg (not routinely added) Fatigue, hypochromic microcytic anemia, glossitis, koilonychia Reproductive-age females, pregnant females, chronic anemias, hemoglobinopathies, post–gastric bypass/duodenectomy, alcoholics PO or IV: hemosiderosis, followed by deposition in liver, pancreas, heart, and glandsIntrinsic: hereditary hemochromatosis Ferritins, TIBCs, % transferrin saturationc, irons Manganese (Mn2+) 2.3 mg/60–100 μg Hypercholesterolemia, dermatitis, dementia, weight lossb Chronic liver disease, iron-deficient populations PO: nonebInhalation: hallucination, Parkinsonian-type symptoms21 No reliable markersManganeses does not reflect bodily stores, especially in the CNS Selenium 55 μg/20–60 μg Myalgias, cardiomyopathyaIntrinsic: Keshan disease (Chinese children), Kashin–Beck disease, myxedematous endemic cretinism22 Endemic areas of low soil content include certain parts of China and |New Zealand10 PO: nausea, diarrhea, AMS, irritability, fatigue, peripheral neuropathy, hair loss, white splotchy nails, halitosis (garlic-like odor) Seleniums, glutathione peroxidase activityb Zinc (Zn2+) 11 mg/2.5–5.0 mg Poor wound healing, diarrhea (high fistula risk), dysgeusia, teratogenicity, hypogonadism, infertility, acrofacial and oral skin lesions (glossitis, alopecia), behavioral changesIntrinsic: acrodermatitis enteropathica Chronic diarrhea, cereal-based diets, alcoholics, chronic liver disease, sickle cell, HIV, pancreatic insufficiency/any intestinal malabsorptive states, fistulas/ostomies, nephrotic syndrome, diabetes, post–gastric bypass/duodenectomy, anorexia, pregnancy19Intrinsic: acrodermatitis enteropathica PO: nausea, vomiting, gastritis, diarrhea, low HDL, gastric erosionsCompetition with GI absorption can precipitate Cu2+ deficiencyInhaled: hyperpnea, weakness, diaphoresis Zincs,p, alkaline phosphatases (good for those on TPN, but in general Zincs,p hair, RBC, WBC levels can be misleading)Zinc radioisotope studies (most accurate tests at present; limited by cost and availability)7 Vitamin ARetinol 900 μg/3300 IU Conjunctival xerosis, keratomalacia, follicular hyperkeratosis, night blindness, Bitot spots, corneal + retinal dysfunction Any malabsorptive state involving proximal small bowel, vegetarians, chronic liver disease Acute: teratogenic, skin exfoliation, intracranial hypertension, hepatocellular necrosisChronic: alopecia, ataxia, cheilitis, dermatitis, conjunctivitis, pseudotumor cerebri, hyperlipidemia, hyperostosis Retinols, retinol estersp, electroretinogram, liver biopsy (diagnostic for toxicity), retinol binding protein (useful in ESRD; accurately assesses blood levels)23 Vitamin DErgocalciferol 5–15 μg/200 IU Rickets/osteomalacia Any malabsorptive state involving proximal small bowel, chronic liver diseaseOf note: those with higher skin melanin content (i.e., darker skin) have low baseline 25-OH vitamin D levels; it is unclear whether this merits their inclusion as an “at-risk” population23 Hypercalcemia, hyperphosphatemia, which can lead to CaPO4 precipitation, systemic calcification +/− AMS +/− AKI 25-OH vitamin DsOf note: lively debate between IOM and Endocrine Society regarding definitions of deficiency, goal serum 25-OH levels, and at-risk populations24,25 Vitamin E(α,γ)-Tocopherol 15 mg/10 IU Hemolytic anemia, posterior column degeneration, ophthalmoplegia, peripheral neuropathySeen in severe malabsorption, abetalipoproteinemia Any malabsorptive state involving proximal small bowel, chronic liver disease Possible increased risk in hemorrhagic CVA, functional inhibition of vitamin K–mediated procoagulants TocopherolMust account for cholesterol/triglyceride ratio: otherwise, higher cholesterol/triglyceride ratio overestimates vitamin E, lower cholesterol/triglyceride ratio underestimates vitamin E16,c Vitamin KPhylloquinone 120 μg/150 IU Hemorrhagic disease of newborn, coagulopathy Any malabsorptive state involving proximal small bowel, chronic liver disease In utero: hemolytic anemia, hyperbilirubinemia, kernicterusIV: flushing, dyspnea, hypotension (possibly related to dispersal agent) Prothrombin timep Vitamin B1Thiamine 1.2 mg/6 mg Irritability, fatigue, headacheWernicke encephalopathy, Korsakoff psychosis, “wet” beriberi, “dry” beriberi Alcoholics, severely malnourished IV: lethargy and ataxia RBC transketolase activityb, thiamineb,u Vitamin B2Riboflavin 1.3 mg/3.6 mg Cheilosis, angular stomatitis, glossitis, seborrheic dermatitis, normocytic normochromic anemia Alcoholics, severely malnourished Noneb RBC glutathione reductase activityp Vitamin B3Niacin 16 mg/40 mg Pellagra dysesthesias, glossitis, stomatitis, vaginitis, vertigoIntrinsic: Hartnup disease Alcoholics, malignant carcinoid syndrome, severely malnourished Flushing, hyperglycemia, hyperuricemia, hepatocellular injuryb N-methyl-nicotinamideu Vitamin B5Pantothenic acid 5 mg/15 mg Fatigue, abdominal pain, vomiting, insomnia, paresthesiasb Alcoholics3 PO: diarrhea Pantothenic acidu Vitamin B6Pyridoxine 1.3–1.7 mg/6 mg Cheilosis, stomatitis, glossitis, irritability, depression, confusion, normochromic normocytic anemia Alcoholics, diabetics, celiac sprue, chronic isoniazid or penicillamine use15 Peripheral neuropathy, photosensitivity Pyridoxal phosphatep Vitamin B7Biotin 30 μg/60 μg Mental status changes, myalgias, hyperesthesias, anorexiac,26 (excessive egg white consumption results in avidin-mediated biotin inactivation) Alcoholics Noneb,26 Biotinp, methyl-citrateu, 3-methyl- crotonyglycineu, 3-hydroxyisovalerateu Vitamin B9Folic acid 400 μg/600 μg Bone marrow suppression, macrocytic megaloblastic anemia, glossitis, diarrheaCan be precipitated by sulfasalazine + phenytoin Alcoholics, celiac or tropical sprue, chronic sulfasalazine use PO: may lower seizure threshold in those taking anticonvulsants Folic acids, RBC folic acidp Vitamin B12Cobalamin 2.4 μg/5 μg Bone marrow suppression, macrocytic megaloblastic anemia, glossitis, diarrhea, posterolateral column demyelination, AMS, depression, psychosis Vegetarians, atrophic gastritis, pernicious anemia, celiac sprue, Crohn disease, patients postgastrectomy or ileal resection Noneb Cobalamin (B12)s, methylmalonic acids,p Vitamin CAscorbic acid 90 mg/200 mg Scurvy, ossification abnormalitiesTobacco lowers plasma and WBC vitamin C13Sudden cessation of high-dose vitamin C can precipitate scurvy Fruit-deficient diet, smokers,13ESRD27 Nausea, diarrhea, increased oxalate synthesis (theoretical nephrolithiasis risk) Ascorbic acidp, leukocyte ascorbic acid

AKI, acute kidney injury; AMS, altered mental status; CNS, central nervous system; CVA, cerebrovascular accident; ESRD, end-stage renal disease; IOM, Institute of Medicine; GI, gastrointestinal; HDL, high-density lipoprotein (cholesterol); RBC, red blood cell; TIBC, total iron bonding capacity; TPN, total parenteral nutrition; TSH, thyroid-stimulating hormone; WBC, white blood cell.

Subscript: b, blood; c, calculated; p, plasma; s, serum; u, urine.

aOnly reported in patients on long-term TPN.

bNever demonstrated in humans.

cOnly able to induce under experimental conditions and/or only been able to induce in animals.

## Special Considerations

• Both the amount and location of prior gut resection influence nutrient needs. Patients with a reduced length of functional small bowel may require additional vitamins and minerals if they are not receiving parenteral nutrition. Table 2-4 provides guidelines for supplementation in these patients.
• Ileal inflammation, resection, inflammatory bowel disease (IBD), and bypass (ileojejunal bypass) can cause B12 deficiency and bile salt loss. Diarrhea in this setting may be improved with oral cholestyramine.
• Proximal gut resection (stomach or duodenum) via partial gastrectomy, Billroth I and II, duodenal switch/biliopancreatic diversion, Roux-en-Y gastric bypass, pancreaticoduodenectomy (Whipple), and sleeve gastrectomy may impair absorption of divalent cations such as iron, calcium, and copper. Copper deficiency is extremely common in post–gastric bypass patients who do not receive routine supplementation.28
• Patients with excessive gastrointestinal (GI) tract losses require additional fluids and electrolytes. An assessment of fluid losses due to diarrhea, ostomy output, and fistula volume should be made to help determine fluid requirements. Intestinal mineral losses may be calculated by multiplying the volume of fluid loss by the fluid electrolyte concentration (Table 2-5).
• Hyperammonemic encephalopathy is an uncommon but serious complication of Roux-en-Y gastric bypass with an estimated mortality rate of 50%.29 Laboratory hallmarks include elevated ammonia, elevated plasma glutamate, hypoalbuminemia, nutritional and essential amino acid deficiencies, and low zinc.30 It does not appear to resolve with replacement of trace elements. Some reports suggest improvement with total parental nutrition after several months; however, data remain limited.31
Table 2-4: Guidelines for Vitamin and Mineral Supplementation in Patients with Severe Malabsorption
 Supplement Dose Route Prenatal multivitamin with mineralsa 1 tablet daily PO Vitamin Da 50,000 units 2–3 times per week PO Calciuma 500 mg elemental calcium tid–qid PO Vitamin B12b 1 mg daily PO – 100–500 μg q1–2 mo SC Vitamin Ab 10,000–50,000 units daily PO Vitamin Kb 5 mg/d PO – 5–10 mg/wk SC Vitamin Eb 30 units/d PO Magnesium gluconateb 108–169 mg elemental magnesium qid PO Magnesium sulfateb 290 mg elemental magnesium 1–3 times per week IM/IV Zinc gluconate or zinc sulfateb 25 mg elemental zinc daily plus 100 mg elemental zinc per liter intestinal output PO Ferrous sulfateb 60 mg elemental iron tid PO Iron dextranb Daily dose based on formula or table IV

aRecommended routinely for all patients.

bRecommended for patients with documented nutrient deficiency or malabsorption.

Table 2-5: Electrolyte Concentrations in Gastrointestinal Fluids
 Location Na (mEq/L) K (mEq/L) Cl (mEq/L) HCO3 (mEq/L) Stomach 65 10 100 – Bile 150 4 100 35 Pancreas 150 7 80 75 Duodenum 90 15 90 15 Mid–small bowel 140 6 100 20 Terminal ileum 140 8 60 70 Rectum 40 90 15 30

There's more to see -- the rest of this topic is available only to subscribers.