🧬 Family & Essentiality

🌿 Plain-Language Summary

Vitamin K₂ is a fat-soluble nutrient involved in calcium regulation and activation of proteins important for bone and vascular physiology. While K₁ is most associated with blood coagulation, K₂ is linked with directing calcium into bones and teeth and away from arteries and soft tissues.

⚗️ Forms of Vitamin K₂

🔬 Molecular & Chemical IDs

• MK-4: C₃₁H₄₀O₂ (CAS 863-61-6)
• MK-7: C₄₆H₆₄O₂ (CAS 2124-57-4)
• Solubility: Fat-soluble; absorption enhanced by dietary fat
• Storage: Found in liver, bone, and extrahepatic tissues

⚡ Functions

• Activates osteocalcin (supports bone mineralisation)
• Activates matrix Gla protein (MGP) (helps prevent vascular calcification)
• Involved in cell growth and apoptosis regulation pathways

🍽️ Absorption & Bioavailability

• Requires bile acids and dietary fat for absorption
• MK-7 has greater bioavailability and longer half-life than MK-4
• Gut microbiota produce small amounts of K₂

🇦🇺 Australian NRVs (NHMRC 2006)

No separate NRV for K₂ — included in total Vitamin K Adequate Intake (AI):

• Men: 70 µg/day
• Women: 60 µg/day
• Pregnancy: 60 µg/day
• Lactation: 60 µg/day

🚨 Deficiency & Excess

Deficiency

Rare; may cause easy bruising, prolonged bleeding, and contribute to reduced bone density.

Excess

No toxicity reported from foods. Caution advised with high-dose supplements in people using anticoagulants.

🥗 Food Sources

• MK-4: Chicken, beef, pork, egg yolks, dairy
• MK-7: Natto, some hard cheeses
• MK-8, MK-9: Certain fermented cheeses

🧪 Testing & Monitoring

• No routine test for Vitamin K₂ status
• PIVKA-II (Protein Induced by Vitamin K Absence/Antagonism-II) may indicate deficiency

🔗 Interactions

• Warfarin & other VKOR antagonists: Require consistent intake and close medical monitoring
• Broad-spectrum antibiotics may reduce K₂-producing gut bacteria

📊 Evidence Snapshot

• 🔬✅ Well-established: Activation of Gla proteins for bone and vascular health
• 🧪⚖️ Promising/mixed: Reduced fracture risk in some clinical trials
• ⚠️❌ Unproven/hype: Broad anti-ageing or cancer prevention claims