Vitamin K2
Vitamin K2 (Menaquinone-7)
Vitamin K2 (Menaquinone-7, or MK-7) is a fat-soluble vitamin derived primarily from fermented foods like natto and produced by gut bacteria, distinct from K1 (phylloquinone) in its longer side chain and superior bioavailability. It is primarily used to activate matrix Gla protein (MGP) and osteocalcin, directing calcium into bones and teeth while preventing pathological calcification of arteries and soft tissues. MK-7 is the preferred K2 form due to its extended half-life of approximately 72 hours compared to MK-4's 6-8 hours, making once-daily dosing effective.
Mechanism of Action
Vitamin K2 acts as an essential cofactor for the enzyme gamma-glutamyl carboxylase (GGCX), which carboxylates specific glutamate residues on vitamin K-dependent proteins (VKDPs) to produce biologically active Gla-proteins. The two most clinically relevant VKDPs are osteocalcin, which binds hydroxyapatite to mineralize bone matrix, and matrix Gla protein (MGP), the most potent known inhibitor of vascular calcification. MK-7 also activates protein S and Gas6, which have roles in anticoagulation and cellular survival signaling, and exhibits some activity through nuclear receptors including the pregnane X receptor (PXR).
Evidence by Health Goal(17 goals)
Dosing Protocols
With a fat-containing meal to optimize absorption
100mcg/day is the standard evidence-based dose for cardiovascular and bone health benefits. 180-200mcg/day has been used in clinical trials showing significant arterial stiffness reduction. Individuals taking high-dose vitamin D3 (>5000 IU/day) may benefit from the higher end of the range to ensure adequate carboxylation of osteocalcin. MK-7 specifically should be used over MK-4 for once-daily dosing due to longer half-life.
Safety & Side Effects
Vitamin K2 (MK-7) has an excellent safety profile at standard doses and no established tolerable upper limit has been set by regulatory agencies, as toxicity has not been demonstrated in human studies. However, it must be used with caution or avoided entirely by individuals on warfarin (Coumadin) or other vitamin K-antagonist anticoagulants, as even moderate doses can significantly alter anticoagulation status.
Possible Side Effects
- !Rare gastrointestinal discomfort at very high doses (>500mcg/day)
- !Potential procoagulant effect in individuals with warfarin-sensitive clotting disorders
- !Headache reported rarely in sensitive individuals
- !Skin rash or hypersensitivity reaction in rare cases
- !Interference with INR stability in anticoagulated patients
Interactions
- -Warfarin (Coumadin) and other vitamin K-antagonist anticoagulants: Even low doses of MK-7 can substantially reduce INR and undermine anticoagulation therapy - contraindicated without close medical supervision
- -High-dose Vitamin D3: Synergistic relationship - vitamin D increases osteocalcin synthesis, increasing demand for K2-dependent carboxylation; co-administration is generally recommended at higher D3 doses
- -Broad-spectrum antibiotics: May reduce gut bacteria that produce endogenous menaquinones, increasing relative K2 deficiency
- -Bile acid sequestrants (cholestyramine, colestipol): Impair absorption of fat-soluble vitamins including K2, reducing efficacy
- -Orlistat (Alli, Xenical): Blocks fat absorption and may significantly reduce K2 bioavailability
Cost & Where to Buy
Price varies significantly by brand, purity, and whether MK-7 is derived from natto (natural) or synthetic sources. Quality brands (e.g., Jarrow, Thorne, Life Extension) typically cost $15-25/month. Budget options exist but should specify MK-7 form and dose clearly on labeling.
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