Vitamin K2 (MK-7)
vitamin K2 · menaquinone · MK-7 · MK-4
A vitamin promoted for directing calcium to bones and away from arteries.
TypeSupplement / dietary
The grade answers: What does the human evidence support for: Bone & vascular health?
Grade
C
Limited
The grade rates evidence quality — it is not advice to take or buy.
- Class
- Fat-soluble vitamin
- Primary use
- Bone & vascular health
- Evidence strength
- low
- Last reviewed
- 2026-07-01
Bottom line
A plausible role in bone and vascular calcium handling, with mostly surrogate-marker evidence. Interesting and safe, but hard clinical-outcome data are limited.
What the evidence says
Vitamin K2 activates proteins (osteocalcin, matrix Gla protein) that help deposit calcium in bone and inhibit its deposition in arteries — a genuinely appealing mechanism. Human trials show it improves these markers and some bone-density measures, and it's often paired with vitamin D. But evidence on hard endpoints (fractures, cardiovascular events) is limited and mixed, and much of the enthusiasm is mechanistic. Grade C: sound biology, thin outcome proof.
Key studies
- [1]
- [2]
Vitamin K2 and arterial calcification · RCT
Signals on vascular markers; outcome evidence sparse.
Open on PubMed ↗ - [3]
Vitamin K-dependent proteins (review) · review
Explains the calcium-routing mechanism.
Open on PubMed ↗
Mechanism
Serves as a cofactor for γ-glutamyl carboxylation of vitamin-K-dependent proteins, activating osteocalcin (bone) and matrix Gla protein (vascular calcification inhibitor).
Safety
Well tolerated with a wide safety margin. Important caveat: vitamin K interacts with warfarin and similar anticoagulants — anyone on those drugs must not change vitamin K intake without medical supervision.
Dosage context
Supplements commonly provide ~90–200 µg/day of MK-7. The MK-7 form has a longer half-life than MK-4; optimal dose and long-term benefit are not settled.
Examples of application
- Taken as MK-7 (~90–200 µg/day), often alongside vitamin D.
- Must not be changed by anyone on warfarin without medical advice.
- Judged on markers; hard-outcome evidence is still limited.
From the field
K2 has one of the more elegant mechanisms in the supplement aisle — and one of the gaps between mechanism and outcomes. We grade it C and flag the warfarin interaction, which the marketing tends to skip.