Here's What You Should Know
Vitamin K exists in two primary forms with very different functions. Vitamin K1 (phylloquinone) concentrates in the liver and controls blood clotting. Vitamin K2 (menaquinone) directs calcium traffic throughout the body — specifically, it activates proteins that tell calcium to deposit in bone and teeth rather than in arteries, kidneys, and soft tissues where it causes harm.
This calcium-directing function makes K2 one of the most under-discussed nutrients in cardiovascular and bone health. Without K2, supplemental calcium and vitamin D have no guidance system — calcium absorbed from food and supplements may calcify arteries rather than bones. The Rotterdam Study found that people with the highest dietary vitamin K2 had a 57% lower risk of dying from heart disease and significantly less aortic calcification than those with the lowest intake.
Signs This May Be Part of Your Pattern
- Arterial calcification or calcium deposits visible on imaging
- Osteoporosis or low bone density despite calcium supplementation
- Kidney stones (calcium oxalate type — misrouted calcium)
- Dental calculus or frequent cavities (mineral routing issues)
- Symptoms worsening after taking high-dose vitamin D without K2
Why This Gets Missed
K2 is not present in most multivitamins in meaningful amounts, and is entirely absent from most standard diets. The primary food sources are fermented foods — particularly natto (fermented soybeans, the highest dietary source by far), certain aged cheeses (Gouda, Brie), and to a smaller extent eggs and butter from grass-fed animals. Grass-fed animal fat and fermented dairy contain MK-4; fermented foods contain MK-7. Most people in modern Western diets get virtually none.
The connection to vitamin D makes this particularly important: vitamin D substantially increases calcium absorption from the gut. If K2 is not simultaneously available to activate the Gla proteins (osteocalcin and matrix Gla protein) that route calcium correctly, the increased calcium absorption has no destination signal.
How It Connects to the Bigger Pattern
K2, vitamin D, calcium, and magnesium form an interdependent quartet for bone and cardiovascular health. Warfarin (the blood thinner) is a direct vitamin K antagonist — patients on warfarin are instructed to avoid vitamin K, but this specifically applies to K1 for clotting effects. K2's role in calcium routing is distinct, though interactions with anticoagulants still require clinical guidance before supplementation.
What to Start With
MK-7 (the fermented-food form) has a longer half-life in the body than MK-4 and is the form used in most research showing clinical benefit. A dose of 90–180 mcg/day MK-7 is the range used in bone density trials. If taking vitamin D3 at doses above 2000 IU daily, K2 should be considered a companion supplement rather than optional. Natto is the best dietary source by far — 100g contains over 1000 mcg of MK-7 — but it's a strong acquired taste.