Vitamin K2 (MK-7)

What it is

A long-chain form of vitamin K (menaquinone-7), distinct from vitamin K1 (phylloquinone, found in leafy greens), with a longer half-life in the body and specific interest for bone and cardiovascular health.

How it works

Activates vitamin K-dependent proteins, notably osteocalcin (which helps bind calcium into bone) and matrix Gla-protein (which helps prevent calcium deposition in arteries).

Who should take it

Adults interested in bone density support, particularly alongside vitamin D and calcium, and those interested in vascular calcification research (an active but still emerging area).

Who should avoid it

Anyone on warfarin or other vitamin K antagonist medications must coordinate any vitamin K intake changes closely with their prescribing physician, as it can significantly affect blood clotting control.

Evidence summary

Several RCTs (notably in postmenopausal women) show improved osteocalcin activation and some improvement in bone mineral density markers; cardiovascular calcification benefit is supported by observational data and some smaller trials, but large definitive outcome trials are still limited.

Scientific mechanism

Serves as a cofactor for gamma-glutamyl carboxylase, an enzyme that activates vitamin K-dependent proteins including osteocalcin (bone mineralization) and matrix Gla-protein (inhibits vascular calcification).

Moderate Evidence — based on high-quality human evidence including systematic reviews, meta-analyses, randomized controlled trials, and major clinical guidance where available.

Ratings reflect the overall quality and consistency of human evidence, not marketing claims. Where evidence is mixed, this is stated explicitly rather than rounded up.

Observational studies and some RCTs suggest MK-7 supports bone mineral density and arterial health by activating calcium-regulating proteins, but the evidence base is smaller and less definitive than for vitamin D or calcium — more large, long-term RCTs are needed.

• ★★★☆☆ Activates osteocalcin, supporting calcium incorporation into bone
• ★★☆☆☆ May help inhibit arterial calcification via matrix Gla-protein activation
• ★★★☆☆ Some evidence for improved bone mineral density markers in postmenopausal women
• ★★☆☆☆ Large, long-term cardiovascular outcome trials are still limited

Side effects

Very well tolerated; no significant side effects reported at studied doses.

Drug interactions

Critically important: antagonizes the effect of warfarin and other vitamin K antagonists — any change in vitamin K intake (including from diet) should be discussed with the prescribing physician and monitored via INR testing.

Who should avoid it / use caution

• With a meal containing some fat to aid absorption, as it is fat-soluble
• Consistent daily timing is more important than time of day for those on blood thinners, to keep intake stable

• Natto (fermented soybeans — highest source)
• Certain aged cheeses
• Egg yolks
• Fermented foods generally

• True dietary deficiency is rare in adults; low status has been associated in observational research with lower bone mineral density and vascular calcification markers, though causation isn't fully established

Key Research Papers

• Review: vitamin K2 as a promoter of bone and cardiovascular health (PMC)
• Systematic review: vitamin K intake and warfarin/VKA interaction (PMC)

General Reference Organizations

• NIH Office of Dietary Supplements — Fact Sheets
• PubMed — U.S. National Library of Medicine

⚕️ This page does not diagnose, treat, cure, or prevent any disease. Vitamin K2 (MK-7) is not a substitute for a varied diet or professional medical care. Always consult a qualified healthcare provider before starting any new supplement, especially if pregnant, breastfeeding, managing a health condition, or taking medication.