Vitamin K is a fat-soluble vitamin group needed for normal blood clotting and involved in bone metabolism. The main dietary form is vitamin K1, also called phylloquinone, found mainly in green leafy vegetables. Vitamin K2 refers to several menaquinones found in some animal and fermented foods and produced by bacteria.
Forms
- Vitamin K1, or phylloquinone, is the main form in most diets and is found in foods such as spinach, kale, broccoli, and vegetable oils.
- Vitamin K2, or menaquinones, includes several related compounds. Sources can include natto, some cheeses, meat, and bacterial production in the gut.
Both forms can support vitamin K-dependent processes, but they differ in food sources, absorption, and metabolism.
Functions
Vitamin K is required for the activation of proteins involved in haemostasis, the process that helps bleeding stop. Prothrombin is one of the vitamin K-dependent clotting proteins.
Vitamin K is also involved in proteins linked with bone metabolism, including osteocalcin. Research continues into how vitamin K status relates to bone health and vascular calcification, but this does not make vitamin K a general treatment for osteoporosis or heart disease.
Food Sources
Sources include:
- Kale, spinach, spring greens, broccoli, and Brussels sprouts.
- Soya bean, rapeseed, and other vegetable oils.
- Natto and some fermented foods.
- Some cheeses, meat, and eggs in smaller or variable amounts.
Because vitamin K is fat-soluble, absorption depends on normal fat digestion and bile flow.
Intake and Deficiency
NHS guidance states that adults need about 1 mcg of vitamin K a day for each kilogram of body weight and that most people should get enough from a varied diet.
Clinically important deficiency is rare in healthy adults. It is more likely in newborns who do not receive vitamin K, people with fat malabsorption, some liver or bile disorders, and people taking medicines that interfere with vitamin K metabolism.
Severe deficiency can cause bleeding because clotting proteins are not activated properly.
Medicine Interactions
Vitamin K interacts with warfarin and similar anticoagulants. People taking these medicines are usually advised to keep vitamin K intake consistent rather than suddenly eating much more or much less.
Newborn babies are commonly given vitamin K to prevent vitamin K deficiency bleeding.
See Also
References
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