Table 1.

Vitamin K: Molecular Forms, Sources, and Contributions to Vitamin K Activity

Molecular Form of Vitamin K	Primary Sources	Dietary Contribution to Vitamin K Activity
Vitamin K1—Phylloquinone	Green leafy vegetables	Major, close to 90%41 Well-absorbed, less active than K2 as an MK-7 form; mainly supports homeostasis35
Vitamin K2—MK-4	Some meats, eggs, and cheeses	Minor as a direct dietary source of vitamin K41 Well-absorbed, less active than K2 as MK-7 form; activates K–dependent proteins outside the liver43
Vitamin K2—MK-7	Natto, cheeses	Minor as a direct dietary source of vitamin K in Europe, the United States, and Australia39,41 Well-absorbed; provides the highest vitamin K activity; activates K–dependent proteins outside the liver44
Long-chain menaquinones (eg, MK-10–MK-13)	Colon bacteria	Minor as a direct dietary source of vitamin K42 Poorly absorbed42 and provides little vitamin K activity37,40

Abbreviations: MK-4, menaquinone 4; MK-7, menaquinone 7; MK-10, menaquinone 10; MK-13, menaquinone 13.