Vitamins and minerals - Vitamin K 

  • Overview

Vitamin K 

Vitamin K has several important functions. For example, it is needed for blood clotting, which means it helps wounds heal properly.

There is increasing evidence that vitamin K is also needed to help build strong bones.

Good sources of vitamin K

Vitamin K is found in:

  • green leafy vegetables, such as broccoli and spinach
  • vegetable oils
  • cereals

Small amounts can also be found in meat and dairy foods.

How much vitamin K do I need?

Adults need approximately 0.001mg a day of vitamin K for each kilogram of their body weight.

For example, someone who weighs 65kg would need 0.065mg a day of vitamin K, while a person who weighs 75kg would need 0.075mg a day.

You should be able to get all the vitamin K you need by eating a varied and balanced diet. 

Any vitamin K that your body does not need immediately is stored in the liver for future use, so you do not need it in your diet every day.

What happens if I take too much vitamin K?

There is not enough evidence to know what the effects might be of taking high doses of vitamin K supplements each day.

What does the Department of Health advise?

You should be able to get all the vitamin K you need by eating a varied and balanced diet. If you take vitamin K supplements, do not take too much because this might be harmful.

Taking 1mg or less of vitamin K supplements a day is unlikely to cause any harm.


Page last reviewed: 26/11/2012

Next review due: 26/11/2014

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The 4 comments posted are personal views. Any information they give has not been checked and may not be accurate.

PlantStrong said on 07 June 2013

@polyhedron

K2 is a con. K1 is converted in to K2 in the human body. So long as you eat enough K1 you will make enough K2. As for calcium Green leafy vegetables are high in these, par spinach, as spinach creates a chemical which stops the calcium in it being absorbed. But all Cruciferous Vegetables have high amounts of calcium and vitamin K1 enough to create enough K2. So don't worry about getting enough K2 if you eat plenty of Cruciferous Vegetables.

http://www.whfoods.com/genpage.php?tname=btnews&dbid=126

If you want to know where the K2 rumors started, here explains: http://www.quackwatch.com/11Ind/mercola.html

If you want to absorb calcium better don't eat spinach with high calcium foods either. Oxalates, a naturally occurring compound, found in many vegetables such as spinach, rhubarb, beet greens, and collard greens, have been found to reduce the absorption of dietary calcium from vegetables.

This explains more: http://askgeorgie.com/calcium-absorption-and-oxalates/

So basically for the best calcium absorption eat Cruciferous Vegetables on there own or with foods that have low Oxalates. :-)

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polyhedron said on 16 December 2012

I absolutely agree with Copo (above as I write).

K1 can indeed be found in green vegetables. But K2 seems to be more widely available from protein sources.

The vitamin K story is considerably more interesting and complicated than the above NHS article. As that story is continuing to develop, there is likely to be much more information available. So please go off and find out what the current state of knowledge is - and do not rely on what it says here.

Also, why on earth are the requirements presented in milligrams? - Which involves using a decimal point and zeroes after the decimal point. Using micrograms makes it so much easier to read. One microgram per kilogram of body weight rather than 0.001 mg per kilogram.

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polyhedron said on 16 December 2012

I absolutely agree with Copo (above as I write).

K1 can indeed be found in green vegetables. But K2 seems to be more widely available from protein sources.

The vitamin K story is considerably more interesting and complicated than the above NHS article. As that story is continuing to develop, there is likely to be much more information available. So please go off and find out what the current state of knowledge is - and do not rely on what it says here.

Also, why on earth are the requirements presented in milligrams? - Which involves using a decimal point and zeroes after the decimal point. Using micrograms makes it so much easier to read. One microgram per kilogram of body weight rather than 0.001 mg per kilogram.

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Copo said on 19 November 2011

No information here about the difference between K1 and K2.
Other sites suggest that K2 is THE vitamin that directs calcium to bones rather than arteries, which seems very important to me.

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