Educational profile — independent, evidence-informed overview. This content is not medical advice. Please consult your healthcare provider for personalised guidance.
🧬 Family & Essentiality
FamilyFat-soluble secosteroids
EssentialityEssential nutrient
FormsD3 (cholecalciferol), D2 (ergocalciferol)
🌿 Plain-Language Summary
Vitamin D helps regulate calcium and phosphate balance, supporting bone mineralisation, muscle function, and immune modulation. D3 can be produced in the skin via sunlight (UVB) or obtained from foods and supplements.
⚗️ Molecular & Chemical IDs
- D3: C₂₇H₄₄O (CAS 67-97-0)
- D2: C₂₈H₄₄O (CAS 50-14-6)
- Transported by vitamin D-binding protein
⚡ Functions
- Facilitates intestinal calcium & phosphate absorption
- Supports bone growth and remodelling
- Modulates immune and inflammatory responses
- Plays a role in muscle function
🍽️ Absorption & Bioavailability
D3Sunlight, fatty fish, liver, fortified foods — higher potency; absorbed with dietary fat
D2Fortified plant milks, UV-treated mushrooms — lower potency; shorter half-life
🇦🇺 Australian NRVs (NHMRC)
- 19–50 yrs: AI 5 µg/day (200 IU)
- 51–70 yrs: AI 10 µg/day (400 IU)
- 70+ yrs: AI 15 µg/day (600 IU)
- UL (adults): 80 µg/day (3200 IU)
AI assumes minimal sun exposure; needs vary with UV exposure, skin type, and lifestyle.
🚨 Deficiency & Excess
Deficiency
Rickets (children), osteomalacia (adults), muscle weakness.
Excess
Hypercalcaemia, kidney stress (usually from very high supplemental doses).
🥗 Food Sources
- Fatty fish, cod liver oil, egg yolks
- Fortified dairy & plant milks
- UV-exposed mushrooms (D2)
🧪 Testing & Monitoring
- Serum 25-hydroxyvitamin D [25(OH)D] is the primary status marker
- Deficiency cut-off: <50 nmol/L
- Typical target range: ~50–125 nmol/L
🔗 Interactions
- Fat-malabsorption reduces uptake
- Glucocorticoids & anticonvulsants may increase breakdown
- Excess vitamin A may antagonise bone effects
📊 Evidence Snapshot
- 🔬✅ Well-established: Calcium homeostasis; prevention of rickets & osteomalacia
- 🧪⚖️ Promising/mixed: Immune modulation; falls prevention in older adults
- ⚠️❌ Unproven/hype: Broad disease prevention in replete individuals
