Vitamin K

Vitamin K is a fat-soluble vitamin named after the initial from the German word, koagulation. Three types of compound have vitamin K activity: phylloquinone (K1), menaquinones (K2) and menadione (K3).

Bacteria in the gut produce some vitamin K2 which can be absorbed and used.

High doses of vitamin K are used to counteract over dose of the blood-thinning drug, warfarin. Seek medical advice before taking supplements containing vitamin K if you are taking warfarin treatment (e.g. for a previous blood clotting disorder). It is unlikely that dietary sources would provide enough vitamin K to interact with warfarin, e.g. you would have to eat the equivalent of 250g broccoli or cauliflower daily to have a significant effect.

Why you need it

Vitamin K is essential for normal blood clotting. It acts as an essential cofactor for the production of clotting proteins II, VII, IX, X, protein C and protein S in the liver.

A single dose of vitamin K (by injection or orally) is offered to all newborn infants to prevent a condition known as haemorrhagic disease of the newborn. This arises during the first few days of life and causes haemorrhage into the brain due to vitamin K deficiency. Some research initially suggested an increased risk of childhood leukaemia associated with giving vitamin K by injection (rather than orally) at birth, but this has now been refuted.

Vitamin K is also needed for the synthesis of osteocalcin - a calcium-binding protein found in bone matrix. Vitamin K is now recognized as being as important for bone health as the mineral, calcium.

Research

Lack of vitamin K has been linked to thinning bones and osteoporosis. In one study, when vitamin K supplements were given to postmenopausal women, bone loss was reduced and their bones became stronger. Research suggests vitamin K supplement can reduce loss of bone calcium in post-menopausal women by up to 50 per cent.

How much you need

No EC RDA for vitamin K is currently set. Requirements are thought to be around 1mcg per kilogram of body weight per day.

Symptoms that may be due to lack of vitamin K include:

prolonged bleeding time
easy bruising
recurrent nose bleeds
heavy periods
diarrhoea
osteoporosis

Foods containing vitamin K include:

cauliflower (richest source)
broccoli
dark green leafy vegetables
kelp
yoghurt
egg yolk
alfalfa
safflower, rapeseed, soya and olive oils
fish liver oils
liver
tomatoes
meat
potatoes
pulses

Bacteria in the gut produce some vitamin K which can be absorbed and used. Seek medical advice before taking supplements containing vitamin K if you are taking warfarin treatment (e.g. for a previous blood-clotting disorder).

Vitamin K

Add Comment