Nutrition Assessment in Nursing Practice

Nutrition assessment is a core nursing skill used to identify malnutrition early and prevent complications such as poor wound healing, infection, muscle wasting, and prolonged hospitalization. This note reviews the four pillars of assessment — dietary history, physical exam, anthropometrics, and labs — along with high-yield thresholds and common exam traps.

Definition

Nutrition assessment is the systematic evaluation of a patient's nutritional status using dietary history, physical examination, anthropometric measurements, and laboratory data. Early identification of malnutrition prevents complications such as poor wound healing, infection, muscle wasting, and prolonged hospitalization.

Components of Nutrition Assessment

• Dietary history — food intake, preferences, allergies, restrictions (e.g., 24-hour recall, food diary).
• Physical examination — signs of malnutrition in hair, skin, nails, and mucous membranes (e.g., brittle hair, dry skin, glossitis).
• Anthropometric measurements — body size and composition (weight, height, BMI, skinfold thickness).
• Laboratory data — protein status, vitamins, minerals (albumin, prealbumin, hemoglobin, electrolytes).

Dietary History Methods

• 24-hour recall: patient lists all foods and beverages consumed in the past 24 hours. Quick, but relies on memory and honesty.
• Food frequency questionnaire: how often the patient eats specific foods. Useful for long-term patterns.
• Food diary: patient records all intake for 3–7 days. More accurate but requires cooperation.

Essential information to collect:

• Usual meal patterns
• Food allergies
• Dietary restrictions (religious, cultural, medical)
• Supplement use
• Appetite changes

For patients with poor intake, assess for dental problems, dysphagia, nausea, vomiting, diarrhea, or depression.

Physical Signs of Malnutrition

Key deficiency clues:

• Angular stomatitis (cracking at mouth corners) — riboflavin (B2) or iron deficiency.
• Glossitis (smooth, swollen tongue) — niacin, iron, or B12 deficiency.
• Koilonychia (spoon-shaped nails) — iron deficiency anemia.

Anthropometric Measurements

• Obtain a baseline weight on admission. Weigh at the same time each day, on the same scale, with the same clothing.
• Body Mass Index (BMI) = weight (kg) ÷ height (m)².

BMI Classification

Significant Weight Loss

• 5% loss in 1 month
• 7.5% loss in 3 months
• 10% loss in 6 months

Unintentional weight loss is more concerning than intentional loss.

Percent weight change = (usual weight − current weight) ÷ usual weight × 100.

Other measures:

• Mid-arm circumference — estimates muscle mass.
• Skinfold thickness — estimates body fat percentage.

Laboratory Markers

• Albumin — reflects long-term protein status (half-life 18–20 days). Low levels suggest chronic malnutrition, liver disease, or kidney disease.
• Prealbumin — reflects short-term protein status (half-life 2–3 days). More sensitive to recent nutrition changes but altered in renal failure.
• Hemoglobin/hematocrit — low in iron, B12, or folate deficiency anemias.
• Total lymphocyte count <1,500 cells/mm³ indicates immunosuppression from protein-calorie malnutrition.

Risk Factors for Malnutrition

• Older adults — decreased appetite, dental problems, social isolation, polypharmacy.
• Chronic diseases — cancer, COPD, heart failure, kidney disease, GI disorders.
• Post-operative patients — increased protein and calorie needs for wound healing.
• Prolonged NPO status or dysphagia — decreased intake.
• Alcohol use disorder — thiamine, folate, B12 deficiencies.
• Low socioeconomic status — limited access to nutritious food.

Mini Clinical Scenarios

Scenario 1

A patient has a normal BMI of 22 but reports unintentional weight loss of 8% over the past month. What is the priority interpretation?

Answer: Malnutrition is present despite normal BMI, because weight loss of ≥5% in one month is clinically significant.

Scenario 2

A patient with end-stage liver disease has an albumin of 2.5 g/dL (normal 3.5–5.0). Can you diagnose malnutrition based on this alone?

Answer: No. Albumin is affected by liver disease and hydration status. Do not rely on albumin alone to diagnose malnutrition in liver disease.

Common Exam Traps

• Do not rely on albumin alone — it is affected by hydration, liver disease, and kidney disease.
• Do not use prealbumin in patients with renal failure — levels are altered.
• Do not ignore unintentional weight loss — 5% in 1 month requires investigation.
• Do not assume normal BMI means adequate nutrition — micronutrient deficiencies can occur at any BMI.

Key takeaways

• Nutrition assessment has four pillars: dietary history, physical exam, anthropometrics, and labs.
• Significant weight loss thresholds: 5% in 1 month, 7.5% in 3 months, 10% in 6 months.
• Albumin = long-term protein status (half-life 18–20 days); prealbumin = short-term (half-life 2–3 days).
• Classic physical signs: brittle hair, dry skin, glossitis, angular stomatitis, koilonychia, poor wound healing.
• Malnutrition can occur even with a normal BMI when significant weight loss has occurred.
• Never rely on albumin alone, and never ignore unintentional weight loss.