RDI
Overdosing
Conception, pregnancy and breastfeeding
Food sources
Vitamin K is a fat-soluble vitamin that is needed for our bodies to form a substance called 'prothrombin'. Prothrombin is one (of many) essential blood components required to create our normal blood clotting mechanism, used to prevent and control excessive bleeding. If the vitamin K levels in our body are low, the person is said to have a 'Vitamin K Deficiency', giving them a tendency to bleed. Vitamin K is also thought to play a role in building strong bones.
Our bodies obtain vitamin K in two ways:
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A small amount comes from the foods that we eat, such as green, leafy vegetables and other green vegetables, cauliflower, vegetable oils, diary products, Soya beans and eggs. This is known as vitamin K1 (or 'phylloquinone'). |
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Most of our vitamin K is obtained through the synthesis of normal bacteria present inside our bowel, and then stored in our liver. This is called vitamin K2 (or 'menaquinone') and is produced in more than adequate amounts to protect us from bleeding, even if our diet is inadequate. |
Vitamin K deficiency is rare in adults. Antibiotics can kill the normal bacteria in the bowel that produce vitamin K and some drugs (such as some taken for epilepsy, barbiturates, drugs to treat tuberculosis and blood thinning medications such as Warfarin) can interfere with the action of vitamin K.
Newborn babies have a natural degree of vitamin K deficiency at birth (usually about 40 to 70% less than adult levels). These levels are usually adequate to protect babies from bleeding, but can be quickly depleted if the baby is unable to replace and build up their Vitamin K stores in the weeks and months following their birth. Babies are usually given an injection (or 3 oral doses) of vitamin K soon after birth. You can read more in
vitamin K.