La nutrición es un determinante fundamental de la salud y la recuperación. Las necesidades nutricionales varían según la edad, el estado de salud, el nivel de actividad y las patologías. La enfermera desempeña un papel clave en la valoración nutricional, la detección de la malnutrición y la educación terapéutica.
- Macronutrientes: hidratos de carbono (4 kcal/g, fuente de energía principal), proteínas (4 kcal/g, reparación tisular), grasas (9 kcal/g, hormonas y vitaminas liposolubles)
- Micronutrientes: vitaminas hidrosolubles (C, grupo B — no se almacenan, aporte diario necesario) y liposolubles (A, D, E, K — se almacenan, riesgo de toxicidad en exceso)
- IMC (Índice de Masa Corporal): peso (kg) / talla² (m²) — normal: 18,5–24,9; sobrepeso: 25–29,9; obesidad: ≥ 30
- Malnutrición: déficit o exceso de nutrientes que afecta la función corporal — detectada por cribado nutricional (MNA, NRS-2002)
- Dietas terapéuticas: hiposódica (insuficiencia cardíaca, HTA), hiperproteica (heridas, quemaduras), diabética (control glucémico)
Nutrition Foundations for Nursing
Understand macronutrients and their caloric values, micronutrients and their roles, fluid requirements, dietary electrolytes, therapeutic diets for common conditions, nutrition label interpretation, and BMI/malnutrition screening in clinical practice.
Macronutrients: Carbohydrates, Proteins, and Fats
Energy sources and their roles in the body
The three macronutrients, carbohydrates, proteins, and fats, serve distinct roles in human physiology. Understanding their caloric density and functions is fundamental to nursing nutrition assessment and patient education.
Carbohydrates, 4 kcal/g
Primary energy source. Simple carbs (glucose, fructose, sucrose) provide rapid energy. Complex carbs (starches, fiber) provide sustained energy and promote GI health. The brain uses ~120g glucose/day. Sources: grains, fruits, vegetables, legumes, dairy. Recommended: 45-65% of total daily calories.
Proteins, 4 kcal/g
Building blocks for tissue repair and growth. Complete proteins (animal sources) contain all 9 essential amino acids. Incomplete proteins (plant sources) must be combined for complete amino acid profile. Functions: enzymes, antibodies, albumin (oncotic pressure), hormones. Recommended: 10-35% of total daily calories, or 0.8 g/kg/day for healthy adults.
Fats, 9 kcal/g
Most calorie-dense macronutrient. Essential for absorbing fat-soluble vitamins (A, D, E, K). Unsaturated fats (olive oil, fish, nuts) are heart-healthy. Saturated fats (animal products) raise LDL cholesterol. Trans fats (hydrogenated oils) are the most harmful. Recommended: 20-35% of total daily calories, <10% from saturated fat.
Macronutrient Functions and Energy
Macronutrients are nutrients needed in large quantities that provide energy (calories). Carbohydrates provide 4 kcal/g and are the body's preferred energy source, the brain relies almost exclusively on glucose. Proteins provide 4 kcal/g and are essential for tissue repair, immune function, enzyme production, and fluid balance (albumin maintains oncotic pressure). Fats provide 9 kcal/g, the most calorie-dense macronutrient, and are essential for hormone synthesis, cell membrane integrity, absorption of fat-soluble vitamins (A, D, E, K), and insulation. Alcohol provides 7 kcal/g but is not classified as a macronutrient because it offers no nutritional value.
Micronutrients and Fluid Requirements
Vitamins, minerals, and hydration
Micronutrients, vitamins and minerals, are required in small amounts but are essential for metabolic processes, immune function, and disease prevention. Adequate fluid intake is equally critical for cellular function, thermoregulation, and waste elimination.
Fat-Soluble Vitamins (A, D, E, K), stored in body fat
Vitamin A:Vision (especially night vision), immune function, skin integrity. Sources: liver, carrots, sweet potatoes. Deficiency: night blindness, xerophthalmia.
Vitamin D:Calcium absorption, bone health, immune modulation. Sources: sunlight, fortified milk, fatty fish. Deficiency: rickets (children), osteomalacia (adults).
Vitamin E:Antioxidant, protects cell membranes. Sources: nuts, seeds, vegetable oils. Deficiency: rare, causes hemolytic anemia.
Vitamin K:Blood clotting (synthesizes clotting factors II, VII, IX, X). Sources: leafy greens, liver. Deficiency: bleeding disorders. Note: interacts with warfarin.
Water-Soluble Vitamins (B-complex, C), not stored, need daily intake
B1 (Thiamine):Energy metabolism. Deficiency: Wernicke-Korsakoff syndrome (alcoholism).
B9 (Folate):DNA synthesis, RBC formation. Critical in pregnancy — deficiency causes neural tube defects.
B12 (Cobalamin):Nerve function, RBC maturation. Deficiency: pernicious/megaloblastic anemia, neuropathy.
Vitamin C:Collagen synthesis, wound healing, immune function, iron absorption. Deficiency: scurvy (bleeding gums, poor wound healing).
Daily Fluid Requirements
General recommendation: 30 mL/kg/day or approximately 2-3 liters/day for adults. Increased needs: fever (add 500 mL per degree above 37°C), burns, diarrhea, vomiting, drains, high environmental temperature, physical exertion. Restricted needs: heart failure, renal failure, SIADH. Monitor intake and output (I&O). Minimum urine output: 30 mL/hr (0.5 mL/kg/hr) indicates adequate renal perfusion.
Dietary Electrolytes
Key electrolytes obtained from diet include: Sodium (Na+), found in processed foods, table salt; regulates fluid balance and nerve impulses; normal: 135-145 mEq/L. Potassium (K+), found in bananas, oranges, potatoes, spinach; critical for cardiac function and muscle contraction; normal: 3.5-5.0 mEq/L. Calcium (Ca²+), found in dairy, leafy greens, fortified foods; essential for bone health, muscle contraction, blood clotting; normal: 8.5-10.5 mg/dL. Magnesium (Mg²+), found in nuts, seeds, whole grains; cofactor in 300+ enzymatic reactions; normal: 1.5-2.5 mEq/L. Phosphorus, found in dairy, meat, beans; partners with calcium for bone health; normal: 2.5-4.5 mg/dL.
Therapeutic Diets
Medical nutrition therapy for common conditions
Therapeutic diets are prescribed as part of the treatment plan for specific medical conditions. Nurses must understand diet modifications to provide accurate patient education, monitor compliance, and recognize when dietary intake may worsen a condition.
Common Therapeutic Diets
Nutrition Labels and Screening
Assessment tools and food label literacy
Nurses must be able to interpret nutrition labels for patient education and understand BMI classification and malnutrition screening tools to identify patients at nutritional risk.
Reading a Nutrition Label
Serving size:All values are per serving — check the number of servings per container.
Calories:Total energy per serving. General guide: 40 calories = low, 100 = moderate, 400+ = high.
% Daily Value (DV):Based on 2,000 calorie diet. 5% DV or less = low, 20% DV or more = high.
Limit these:Saturated fat, trans fat, sodium, added sugars.
Get enough of:Fiber, vitamin D, calcium, iron, potassium.
Ingredient list:Listed by weight in descending order — first ingredient is present in the greatest amount.
BMI and Malnutrition Screening
BMI categories: Underweight (<18.5), Normal (18.5-24.9), Overweight (25.0-29.9), Obese Class I (30.0-34.9), Obese Class II (35.0-39.9), Obese Class III (≥40.0). Malnutrition screening tools include the Malnutrition Screening Tool (MST), Subjective Global Assessment (SGA), and Mini Nutritional Assessment (MNA) for elderly patients. Key lab markers: serum albumin (<3.5 g/dL indicates chronic malnutrition, half-life 18-20 days), prealbumin (<17 mg/dL indicates recent nutritional changes, half-life 2-3 days, more sensitive to acute changes), and transferrin. Unintentional weight loss of >5% in 1 month or >10% in 6 months is clinically significant and warrants nutritional intervention.
Match the Nutrition Concept
Terms
Definitions
Nutrition Foundations Quiz
1/20Which macronutrient provides the most calories per gram?
Nursing Responsibilities
La enfermera valora el estado nutricional (peso, IMC, apetito, capacidad para alimentarse), identifica a los pacientes en riesgo de malnutrición y deriva a la dietista si es necesario. Vigila la tolerancia a las comidas y suplementos, asiste a los pacientes con dificultades para alimentarse y educa sobre las dietas prescritas. Monitoriza los signos de deficiencias vitamínicas o minerales (piel, cabello, mucosas).
Clinical Pearls
La vitamina K es antagonista de la warfarina — los pacientes anticoagulados deben mantener un aporte estable de verduras de hoja verde (no necesariamente evitarlas). El magnesio a menudo se olvida pero es esencial: su déficit agrava la hipopotasemia y la hipocalcemia. Los pacientes postoperatorios, quemados o con heridas crónicas tienen necesidades proteicas elevadas — hasta 1,5–2 g/kg/día.
Patient Education
Adapte los consejos a la dieta prescrita. Para una dieta hiposódica: identificar las fuentes ocultas de sal (conservas, embutidos, quesos). Para una dieta diabética: comprender el índice glucémico y la importancia de las comidas regulares. Valore los cambios progresivos en lugar de las restricciones estrictas para favorecer la adherencia.
Key Takeaways
- Las proteínas son esenciales para la cicatrización y la reparación tisular — las necesidades aumentan en caso de enfermedad o lesión
- Las vitaminas liposolubles (A, D, E, K) pueden acumularse y ser tóxicas — atención a la suplementación no controlada
- La valoración nutricional es un componente de la valoración enfermera completa — no solo de la dietética
- Las dietas terapéuticas deben ser comprendidas y aceptadas por el paciente para ser eficaces