The basics
Vitamin K is not a single vitamin, but a group of related fat-soluble vitamins. This group includes a compound called phylloquinone, also known as vitamin K1, and a series of menaquinones which are commonly referred to as vitamin K2.
What does vitamin K do?
Vitamin K is a trace nutrient essential for the normal function of several proteins in the body. These proteins have very specific roles that are needed for human health.
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Bone health
Vitamin K2 is involved in the body’s ability to produce, and maintain normal healthy bones, through its role in the formation osteocalcin - a protein produced in bone matrix. Osteocalcin binds with calcium and results in calcium being deposited into bones and bone mineralisation.
Some studies have suggested that low vitamin K levels may be associated with an increased risk of fractures, and reduced bone health
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Blood coagulation
Vitamin K is essential for several proteins involved in blood clotting. These vitamin K dependant blood-clotting factors form the ‘coagulation cascade’ which helps our blood to coagulate and stop us from bleeding
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What’s the difference between vitamin K1 and K2?
While they are related, there are many differences between vitamin K1 and vitamin K2 – including their chemical structure, the way they work in the body, how they are metabolised and the foods they can be found in.
After absorption Vitamin K1 is stored in the liver, and used to make clotting factors. However, vitamin K2 is packaged into lipoproteins and released into the bloodstream, where it then travels to the bones.
What foods contain vitamin K?
Vitamin K1 is found in green leafy vegetables such as spinach, broccoli, Brussels sprouts, and kale.
Vitamin K2 is primarily bacterial in origin and found in foods such as cheese, cheese curd and fermented foods – in particular Natto (a traditional Japanese fermented soy bean food).