Clinical meaning
Nutrition is fundamental to health, healing, and disease prevention. The practical nurse must understand the principles of balanced nutrition, perform nutritional assessment, identify patients at nutritional risk, and implement nutritional interventions as part of comprehensive patient care. Macronutrients provide energy: carbohydrates (4 kcal/g -- primary energy source, especially for the brain; sources include grains, fruits, vegetables, legumes), proteins (4 kcal/g -- essential for tissue building and repair, enzyme and hormone synthesis, immune function; sources include meat, fish, dairy, legumes, eggs), and fats (9 kcal/g -- energy storage, cell membrane structure, hormone synthesis, absorption of fat-soluble vitamins A, D, E, K; sources include oils, nuts, avocado, fatty fish). Micronutrients are vitamins and minerals required in smaller quantities but essential for metabolic functions: water-soluble vitamins (B-complex, vitamin C -- not stored significantly, require regular intake), fat-soluble vitamins (A, D, E, K -- stored in liver and adipose tissue, toxicity possible with excess supplementation), and minerals (calcium, iron, zinc, magnesium, potassium, sodium, phosphorus). Total daily energy requirements vary by age, sex, activity level, and clinical condition; basal metabolic rate accounts for approximately 60-70% of total energy expenditure. Nutritional requirements increase significantly during illness, surgery, wound healing, pregnancy, lactation, and growth periods. Malnutrition encompasses both undernutrition (inadequate caloric or nutrient intake) and overnutrition (excessive caloric intake leading to obesity), both of which adversely affect health outcomes.