Vitamin K1 (Phylloquinone)
Essential Vitamins & Minerals · 8 specs
Direct Answer
Vitamin K1 is a fat-soluble naphthoquinone synthesized by photosynthetic plants. Adequate Intake (AI) is 120µg (men) / 90µg (women), acting as an essential cofactor for gamma-glutamyl carboxylase in blood clotting and osteocalcin bone mineralization.
Source: NIH Office of Dietary Supplements / USDA · Last reviewed Aug 28, 2026
Specs
| Nutrient Type | Fat-Soluble Naphthoquinone Vitamin |
| Adult Adequate Intake (AI) | 120 µg / day (Men) / 90 µg / day (Women) |
| Tolerable Upper Limit (UL) | None Established (No adverse effects reported) |
| Chemical Forms | Phylloquinone (K1 - Green Plants), Menaquinones (K2: MK-4, MK-7 - Ferments/Animal) |
| Primary Biological Function | Gamma-glutamyl carboxylase cofactor (Factors II, VII, IX, X), Osteocalcin carboxylation, Matrix Gla Protein (MGP) vascular calcification inhibitor |
| Deficiency Condition | Coagulopathy, Hemorrhage, Impaired bone density |
| Top Whole Food Sources | Spinach, Kale, Broccoli, Brussels Sprouts, Natto (K2 MK-7), Parsley |
| Warfarin / Anticoagulant Interaction | Direct competitive antagonist to Coumadin/Warfarin (requires consistent daily intake) |
Matrix Gla Protein (MGP) & Arterial Health
Vitamin K carboxylates Matrix Gla Protein (MGP) in blood vessel walls, actively preventing calcium from depositing as arterial plaque and directing it into bone hydroxyapatite.
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