What Is Vitamin K?
Vitamin K is a fat-soluble vitamin existing in two main forms: K1 (phylloquinone) from plants and K2 (menaquinone) from animal products and fermented foods. Vitamin K is critically important for bone metabolism — it activates osteocalcin, a protein that anchors calcium to the bone matrix.
📊 Forms of Vitamin K
| Form | Type | Sources | Function |
|---|---|---|---|
| Vitamin K1 (phylloquinone) | Plant-based | Leafy greens, spinach, cabbage | Blood clotting |
| Vitamin K2 MK-4 | Animal-based | Liver, egg yolks, butter | Bone metabolism, short half-life |
| Vitamin K2 MK-7 | Fermented | Natto (fermented soy) | Bone metabolism, long half-life (3 days) |
| Vitamin K2 MK-8/MK-9 | Fermented | Cheeses, sauerkraut | Bone and dental health |
🏋️ Benefits for Athletes
🦴 Bone Strengthening
Vitamin K2 activates osteocalcin, which binds calcium in the bones. This is especially important for runners, jumpers and strength athletes, whose bones experience high loads. K2 acts as a calcium driver — directing calcium where it is needed.
🫀 Heart Protection
Vitamin K2 activates MGP (Matrix Gla Protein), which prevents calcium from accumulating in the arteries. For athletes with high calcium intake, this helps prevent arterial calcification.
💪 Calcium Efficiency
Without vitamin K, calcium can accumulate in soft tissues rather than in bones. K2 directs calcium where it is needed, ensuring maximum benefit for bones and joints.
🩸 Injury Prevention
Sufficient vitamin K levels ensure faster bone healing after stress fractures — a common injury for athletes during running and contact sports.
📋 Recommended Doses
- RDA: 90-120 μg per day for adults (K1 only)
- For athletes: 100-200 μg K1 + 45-180 μg K2 (MK-7) per day
- Optimal K2 form: MK-7 (longest half-life, most effective for osteocalcin activation)
- Synergy: Vitamin K works synergistically with vitamin D and calcium. D3 increases osteocalcin production, and K2 activates it
- Warning: If you take blood-thinning medications (warfarin), you must consult a doctor before taking vitamin K
🛒 Recommended Products
🥗 Best Food Sources
| Product | Amount (100 g) | Type | Additional benefit |
|---|---|---|---|
| Natto (fermented soy) | 1,103 μg | K2 MK-7 | Protein, probiotics |
| Leafy cabbage (kale) | 817 μg | K1 | Calcium, antioxidants |
| Spinach (cooked) | 494 μg | K1 | Iron, magnesium |
| Broccoli (cooked) | 141 μg | K1 | Vitamin C, fiber |
| Egg yolk | 15-30 μg (1 pc.) | K2 MK-4 | Protein, choline |
| Gouda cheese | 75 μg | K2 MK-8/9 | Calcium, protein |
❓ FAQ
Is Vitamin K2 Necessary If I Take Vitamin D?
Highly recommended. Vitamin D increases calcium absorption but does not dictate where that calcium should go. Vitamin K2 directs calcium to the bones, not the arteries. The D3 + K2 combination is one of the most important for bone health.
How Do K1 and K2 Differ?
K1 is mainly used for blood clotting in the liver. K2 circulates longer and reaches the bones and blood vessels. K2 is 3-5 times more effective in bone mineralization than K1.
Can You Overdose on Vitamin K?
Vitamin K toxicity is very rare. No upper safe limit has been established. The only exception is people taking anticoagulants (warfarin).