Vitamin A

🧬 Family & Essentiality

🌿 Plain-Language Summary

Vitamin A supports vision, immune regulation, cell growth, and epithelial tissue integrity. Retinoids are active forms, while carotenoids are converted in the body to retinol as needed.

⚗️ Molecular & Chemical IDs

• Retinol: C₂₀H₃₀O (CAS 68-26-8)
• β-Carotene: C₄₀H₅₆ (CAS 7235-40-7)
• Solubility: Fat-soluble; absorption improves with dietary fat
• Storage: Primarily in the liver (stellate cells)

⚡ Functions

• Vision (rhodopsin formation in low-light vision)
• Supports mucosal integrity and immune defence
• Cellular differentiation, growth, and reproduction

🍽️ Absorption & Bioavailability

Conversion of dietary β-carotene to retinol is approximated at ~12:1, but varies by genetics, diet, and health status.

🇦🇺 Australian NRVs (NHMRC)

• Adult men: 900 µg RAE/day
• Adult women: 700 µg RAE/day
• Pregnancy: 800 µg RAE/day
• Lactation: 1100 µg RAE/day
• UL (adults): 3000 µg RAE/day

🚨 Deficiency & Excess

Deficiency

Night blindness, xerophthalmia, dry skin, and higher infection risk.

Excess

• Preformed retinoids: nausea, headaches, liver toxicity, teratogenic in pregnancy
• Carotenoids: benign carotenodermia (yellow-orange skin tint)

🥗 Food Sources

• Preformed: Liver, cod liver oil, dairy, eggs
• Provitamin A: Carrots, sweet potato, pumpkin, leafy greens, mango, apricot, capsicum

🧪 Testing & Monitoring

• Serum retinol (<0.7 µmol/L suggests deficiency)
• Retinol-binding protein (RBP) as a proxy
• Testing not routine unless risk factors present

🔗 Interactions

• Zinc status influences retinol transport
• Orlistat & bile acid sequestrants reduce absorption
• Excess alcohol depletes stores

📊 Evidence Snapshot

• 🔬✅ Well-established: Vision, epithelial integrity, immune function
• 🧪⚖️ Promising/mixed: Observational links with carotenoid intake
• ⚠️❌ Unproven/hype: Broad performance or anti-ageing claims