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  • Writer's pictureBeverley Mort

Vitamin K - What is it and why is it important?

Vitamin K is rarely talked about. Most of us know or have heard about vitamins A, B group, C, D and E, but vitamin K does not get that much press. Why is that?? Vitamin K is important mainly for blood clotting, bone formation, as well as for fighting infections and producing energy. We don’t hear about this vitamin because it is quite rare for a healthy adult to be deficient in vitamin K.

If you have ever had a baby, you might remember signing a consent form for your newborn to receive a vitamin K injection. I did, but I didn’t really know why. It’s because babies are born with a sterile gut (not colonised with bacteria). This happens when they start being exposed to the outside world and in particular if they are breast fed (Mum’s breast milk is the best for colonising baby’s gut with ‘friendly’ bacteria.) It is our gut bacteria that produce a key source of vitamin K, and new born babies are potentially at high risk of bleeding as they are vitamin K deficient, and have immature liver function and clotting of blood function. It’s the vitamin K that helps with the clotting of blood in these circumstances.

When talking about vitamin K though we need to consider that there are two sources; vitamin K1 (also known as phylloquinone), which can be obtained from a healthy well balanced diet rich in green leafy vegetables, kelp, lettuce, broccoli, peas and lentils, and vitamin K2 (also known as menaquinone) – this version is produced by our gut bacteria, but there are some dietary sources such as eggs, dairy and meat, as well as some fermented food – cheese and yoghurt. Our gut bacteria are also able to convert vitamin K1 from our diet to vitamin K2 as necessary.

It is quite rare for an individual to be deficient in vitamin K, however there is evidence to suggest that a poor diet containing very little green leafy vegetables, people who regularly use wide spectrum antibiotics, people with kidney disease or suffering from eating disorders, those taking anti-coagulation medication, and the elderly, are at risk.

There is little scientific research done looking at the benefits of vitamin K supplementation in healthy adults, but reviews of what research has been done has proven inconclusive. Most research is in adults suffering from health conditions such as cystic fibrosis and osteoporosis, as well as neonates and adults taking anti-coagulation medication. In these cases, (apart from those taking anti-coagulants) there is some evidence of benefits, but mainly results are inconclusive, so more research is needed.

The European Food Safety Authority recommends a so called adequate intake for men and women above the age of 18 years of 70 micrograms/day. There is not sufficient evidence of toxicity to set an upper limit for intake of vitamin K, so none is advised. It’s interesting to know that only 75g of cooked kale provides 531 micrograms of vitamin K1. So this vitamin can easily be obtained from following a healthy diet. But… this source of vitamin K can have a low bioavailability, so to enhance absorption its advised that dietary consumption is accompanied by a source of healthy fat or oil.

Care must be taken however that if an individual is taking anti-coagulant drugs such as warfarin then vitamin K intake should be controlled. It is therefore advised that such a person should seek advice from a GP or dietitian on vitamin K intake when taking anti-coagulant medication.

The best way to ensure you do not become vitamin K deficient is to ensure you are eating a healthy balanced diet that includes plenty of green leafy vegetables. I would also recommend taking a wide spectrum probiotic supplement to keep the balance of ‘friendly’ bacteria high so that production of vitamin K2 is optimised naturally in the body.


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