What is Vitamin K?

Vitamin K food sources.

Vitamin K is a fat-soluble vitamin that can be found in five different forms. The "K" comes from the German word koagulations, which means coagulant in English. It is aptly named since vitamin K is necessary for blood to clot, a physiological process essential to human health.(1)

Why is Vitamin K Important?

Coagulation is a complex, multi-step mechanism in the blood called hemostasis. In order to survive an injury to blood vessels, the body must:(12)

Vitamin K is a crucial ingredient for the body to make the proteins in the liver needed for hemostasis. It is not stored in large quantities in the body, but there are many good sources of vitamin K in the food we eat.(12)

Sources and Types of Vitamin K

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Even though there are five different forms of vitamin K, only two of the five (K1 and K2) occur without further synthesis in nature. Vitamin K1 is considered the main dietary form. Parsley, kale, spinach, and broccoli are particularly good food sources for vitamin K1.(34)

Table 1: Vitamin K Types, Sources, and Uses
Form Source Commonly Used For and/or Known Benefits
  • Dark green vegetables.(5)
  • Yellow vegetables.(5)
  • Organ meat (e.g., liver).(6)
  • Oils and margarines made from plants.(1)

To treat:(1)

Vitamin K1 is also used to prevent hemorrhagic disease in babies and osteoporosis.(1)

  • Fermented foods (e.g., cheese and natto)(4)
  • Synthesized by bacteria in meat, cheese, and eggs.(1)
  • Some produced by bacteria in the lower bowel and colon.(13)
  • Some can be made from K1 in the pancreas, artery walls, and testes.(1)

Used to treat:(1)

K3 Synthetic form of vitamin K.(4)
K4 Water-soluble salt of vitamin K3.(1)
  • Used to treat clotting disorders caused by vitamin K deficiency.(1)
K5 Synthetic form of vitamin K.(8)
  • Antibacterial and antifungal properties.(9)
  • Antiviral.(10)
  • Food preservative.(8)
  • Kills chemoresistant cancer cells.(7)

Optimize Your Intake of Vitamin K

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Want to maximize how much vitamin K you get from your diet? Try adding butter (or other fats, such as oil) to your dark green or yellow veggies. Experts say it increases absorption of vitamin K.(1)

Also known as phylloquinone, 2-metyl-3-phytyl-1, 4-napthoquinone, phytonadione, methylphytyl naphthoquinone, and phytomenadione.(135)
Such as olive oil and canola oil; soybean is especially high in vitamin K.(4)
Also known as 2-methyl-3-multiprenyl-1,4 naphthoquinones, MK-1 through MK-13 menaquinones, and menatetrenone.(13)
Fermented soybeans.(4)
Also known as menadione, menadione sodium bisulfite, and 2-methyl-1,4-naphthoquinone.(1)
Also known as menadiol sodium diphosphate; menadiol diacetate; menadiol sodium phosphate; and menadiolum solubile methylnaphthohydroquinone.(1)
Also known as 4-amino-2-methyl-1-naphthol.(1)