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BI8.1-6 | Vitamins and Nutrition — Part 3
Nutritional Assessment
Key Biochemical Markers of Nutritional Status
| Marker | Normal Range | What It Measures | Half-Life | Limitations |
|---|---|---|---|---|
| Serum albumin | 3.5-5.0 g/dL | Chronic protein-calorie status | 20 days | Also falls in inflammation, liver disease, nephrotic syndrome |
| Prealbumin (transthyretin) | 15-35 mg/dL | Acute protein status changes | 2 days | Falls in inflammation (negative acute phase reactant) |
| Serum ferritin | 12-150 µg/L (female); 12-300 µg/L (male) | Iron stores | N/A (storage protein) | Rises in inflammation (acute phase reactant); normal ferritin does not exclude iron deficiency in infection |
| 25-OH-Vitamin D | 30-100 ng/mL (sufficient) | Vitamin D status (storage form) | 2-3 weeks | Does not reflect active calcitriol; varies seasonally |
| Serum B12 | >200 pg/mL (sufficient) | B12 stores | N/A | Can be falsely normal in liver disease; methylmalonic acid more specific |
| Retinol-binding protein | 3-6 mg/dL | Vitamin A transport; acute nutrition | 12 hours | Falls in zinc deficiency, liver disease |
Nutritional assessment is a core clinical skill (BI8.5, BI8.6). It uses four components — the ABCD framework:
Figure: Nutritional Assessment
A — Anthropometric measurements:
- Weight, height, BMI (kg/m²)
- Mid-upper arm circumference (MUAC) — field tool for acute malnutrition in children
- Waist circumference (central obesity risk)
- Skinfold thickness — estimates body fat
- Z-scores: weight-for-age, height-for-age, weight-for-height (WHO growth charts)
- Stunting (low height-for-age) = chronic undernutrition; Wasting (low weight-for-height) = acute
B — Biochemical markers:
- Serum albumin (half-life 20 days — chronic protein status)
- Serum transferrin / prealbumin (shorter half-life — acute protein status)
- Haemoglobin and iron studies (iron deficiency anaemia — India's largest nutritional deficiency)
- Serum vitamin levels (25-OH-D, retinol, B12, folate)
- Blood glucose, lipid profile
C — Clinical examination:
- Skin, hair, nails, mucous membranes, eyes — specific signs of vitamin/mineral deficiency
- Muscle wasting, oedema (kwashiorkor)
D — Dietary assessment:
- 24-hour dietary recall, food frequency questionnaire, food diary
- Compared against ICMR Recommended Dietary Intakes for Indians
India-specific context: India carries a double burden — undernutrition (50% of under-5 children stunted/wasted) AND overnutrition (diabetes, obesity epidemic in urban populations).
SELF-CHECK — : B Vitamins and Nutrition
A 25-year-old vegetarian presents with fatigue and tingling in both feet. Blood film shows macrocytic red cells and hypersegmented neutrophils. The MOST important next investigation is:
A. Serum folate
B. Serum B12
C. Serum ferritin
D. Thyroid function tests
Reveal Answer
Answer: B. Serum B12
A 2-year-old child has stunting (height-for-age Z-score −3.5) but normal weight-for-height. Which term best describes this child's nutritional status?
A. Acute wasting
B. Kwashiorkor
C. Chronic stunting (linear growth retardation)
D. Marasmus
Reveal Answer
Answer: C. Chronic stunting (linear growth retardation)