Japanese fracture studies used prescription MK-4 45 mg/day for years; this is not an ordinary supplement dose
Reviewed · Published
Vitamin K
Required to carboxylate clotting factors and bone-related proteins.
Established functions
- Required to carboxylate clotting factors and bone-related proteins.
Dietary sources
- natto
- komatsuna
- broccoli
Claims and evidence
Claims that Vitamin K alone prevents or treats disease, or invariably improves health without deficiency, are unsupported.
Japanese reference amounts
- Japanese adults (age and sex as specified): Adults: 150 µg/day (AI)
Amounts studied
- Japanese fracture studies used prescription MK-4 45 mg/day for years; this is not an ordinary supplement dose
Tolerable upper limits
- No UL is established; anticoagulant interaction remains the key safety issue.
Forms and bioavailability
Supplement forms: phylloquinone K1, menaquinone-7 MK-7
- Fat-soluble; MK-7 has a longer blood half-life than K1, without proving clinical superiority.
Safety and interactions
Adverse effects
- few adverse effects at ordinary intakes
Medicine and nutrient interactions
- warfarin and other vitamin-K antagonists
Contraindications and cautions
- During anticoagulation, keep intake consistent and consult the prescriber.
Practical selection
- Compare Vitamin K amount per serving, form, allergens, and batch testing; prefer a single-ingredient product suited to the intended use.
Sources and review
- Dietary Reference Intakes for Japanese (2025)Ministry of Health, Labour and Welfare (Japan)
- NIH ODS vitamin fact sheetsNIH Office of Dietary Supplements
Daiki Minaki (editorial and evidence review) ·
Frequently asked questions
How is Vitamin K different from its broader supplement category?
Required to carboxylate clotting factors and bone-related proteins. Compare its named form and amount rather than assuming every category product supplies it.
View detailsWhat safety detail matters specifically for Vitamin K?
warfarin and other vitamin-K antagonists During anticoagulation, keep intake consistent and consult the prescriber.
View details