Vitamin K

The fat-soluble vitamin K is essential for the functioning of several proteins involved in blood clotting (1). There are two naturally occurring forms of vitamin K: vitamin K1 (phylloquinone) is synthesized by plants; Vitamin K2 forms (menaquinones) can be found mainly in dairy products and are also produced to a minor extent by bacteria in the digestive tract of animals (2).

Next to its classical role in blood clotting, several potential health benefits are described for vitamin K. There is increasing scientific evidence that different forms of vitamin K have varying and accentuated impacts on disease risk reduction.

Authored by Dr Peter Engel in 2010, reviewed and updated by Dr Szabolcs Peter on 18.06.2017

Health functions

Vitamin K plays an essential role in blood clotting as well as healthy bone growth and development.

Disease risk reduction

Large epidemiological studies have demonstrated a relationship between vitamin K and age-related bone loss (osteoporosis).

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Things to know about Vitamin K

  • Intake recommendations

    The recommended dietary allowance (RDA) of vitamin K1 (phylloquinone) is dependent on age, gender, and other factors.

  • Supply situation

    Surveys in some European countries have provided estimated mean dietary intakes for vitamin K: in the United Kingdom, an average intake of 68 micrograms (mcg) per person per day was established (28), while in The Netherlands mean daily per capita intake was estimated to be up to 250 micrograms (mcg) (29).

  • Deficiency

    Overt vitamin K deficiency results in impaired blood clotting, usually demonstrated by laboratory tests that measure clotting time.

  • Sources

    Foods high in vitamin K (phylloquinone) include green leafy vegetables like kale, parsley, and broccoli, and some vegetable oils.

  • Safety

    In healthy subjects, there is no known safety risk associated with high doses of vitamin K1 (phylloquinone) or vitamin K2 (menaquinone) forms of vitamin K (27).

  • References

    Consult the full list of scientific references.