What is vitamin K for?

The origin of vitamin K


The vitamin K can be synthesized by plants and bacteria but not humans. The official nomenclature establishes the name of vitamins Kn (K1, K2) when the structure resembles a molecule called “phylloquinone” and of vitamins MKn (MK6, MK10, etc.) when the structure resembles a molecule called “menaquinone”.

But before this classification existed, there was talk of “vitamin K1-n” when the molecule was a phylloquinone and of “vitamin K2-n” when it was a menaquinone, “n” being a number that differentiates them. Without going into more detail, this is the reason why food supplements put names like “Vitamin K2 – menaquinone 7” on the label: they are using both nomenclatures.

The filoquinonas are of plant origin , while menaquinones are synthesized by bacteria . Different forms of vitamin K have different potencies in the body, with menoquinones being more potent than phylloquinones.

Although our intestinal bacteria are capable of synthesizing vitamin K, this activity is not enough, so we will need to obtain vitamin K from the diet.

In what foods do we find vitamin K?


Foods rich in vitamin K, especially rich in phylloquinones, are:

  • Broccoli
  • Cabbage
  • The kale
  • Lettuce
  • The spinach
  • The olive oil
  • Soybean oil


Foods rich in vitamin K, especially rich in menaquinones, are found in products fermented by bacteria such as:

  • The cheese
  • Sauerkraut
  • Pork products
  • Avian products

You can find more information about foods that are rich in vitamin K in our article: Foods rich in vitamin K.

What are the effects of a lack of vitamin K?


Lack of vitamin K causes coagulopathies, that is, difficulty in clotting the blood. This can cause subcutaneous bleeding and even anemia in more serious cases.

In humans, the risk of vitamin K deficiency is increased in older adults, in adults with chronic kidney problems, and in newborns.

The problem with newborns is that they do not have vitamin K reserves, they do not have an intestinal flora that synthesizes it, and breast milk is not very rich in vitamin K, so in the first three months of life there may be a risk of suffer from hemorrhagic disease of the newborn.

If you want to know the functions of vitamin K, you can read them in our article: The functions of vitamin K. 



How to avoid the problems of lack of vitamin K?


To avoid the lack of vitamin K in newborns, it has been chosen in many countries to give a dose of vitamin K intramuscularly to the newborn, rapidly increasing its reserves.

There are medical situations, such as in the case of some heart problems or venous thromboembolism, in which it is necessary to control blood clotting. To do this, drugs called “vitamin K antagonists” can be used, that is, drugs that will not allow vitamin K to act, preventing clotting. Among them are warfarin and acenocoumarol (Sintrom®).

In these cases, it is vitally important to control the amount of vitamin K in the diet, since changes in the daily or weekly dose of vitamin K may cause the amount of medicine to be changed.

Except in babies, in few cases supplementation with vitamin K is necessary, since it is rare that the diet does not contain the minimum amounts that are needed per day.

Recommended amount of vitamin K recommended in an adult


An adult needs between 50 and 120 micrograms of vitamin K per day, depending on age and sex, and it is easy to obtain with a balanced diet.

There is no established upper limit for vitamin K intake, although there are some reported cases of risk of kidney disease with continued and abusive use of phylloquinones.
Unless you are in a risk group, or your doctor advises, routine vitamin K supplementation is not necessary.