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Vitamin K: The underestimated vitamin

Almost everyone has heard or read something about the B vitamins and vitamins C, E or D - in contrast to the underestimated vitamin K. Although most vitamins have been researched more than once, this vitamin has been studied relatively little compared to the others. One thing is certain, however: according to current knowledge, it offers you numerous interesting benefits. You should therefore definitely get to know them.

What is vitamin K?

The vitamin belongs to the group of fat-soluble vitamins. These also include vitamins A, E and D. On the one hand, the vitamin itself is rather unknown, but on the other hand, one effect is very common - the formation of blood clotting factors. For this reason, it is administered prophylactically to newborn babies, for example, to prevent cerebral haemorrhages.

Note: Like other vitamins, the vitamin also occurs in various forms.

Vitamin K1

Vitamin K1 (also known as phylloquinone) is naturally present in some foods - predominantly in green leafy vegetables. It is first metabolised in the liver, where it subsequently forms blood clotting factors. Vitamin K1 is therefore also the form that is used to prevent bleeding in newborn babies.

Vitamin K2

In contrast to the other forms of vitamin, vitamin K2 (menaquinone) is even partially produced from animal or fermented foods by intestinal bacteria and then transported to the blood vessel walls or other tissues close to the liver. There, vitamin K2 takes on tissue-specific functions. The body can only produce small amounts of vitamin K2 itself, which is not sufficient for an adequate supply. It therefore makes sense to take food supplements. Our new product vitamin D3-K2 also contains menaquinone.

Vitamin K3

Menadione (vitamin K3) is neither found in food nor is it produced by intestinal bacteria. It is a synthetically produced vitamin that is not exactly harmless, as it even causes toxic side effects. This is why it is now banned for human consumption.

Benefits and functions

The vitamin is responsible for blood clotting. But what else is it responsible for?

Relieving menstrual cramps with vitamin K

A study of menstruating women aged 18-55 found the following: The group that supplemented with the vitamin suffered less heavy bleeding during their periods than the other group. The longer the study lasted, the more women experienced this effect.

Vitamin K for strong bones

Vitamin K activates osteocalcin, which is important as it promotes calcium incorporation in the bones. To do this, however, it needs the help of vitamin D, which converts the precursor of osteocalcin into the active form. Once this has happened, calcium can be incorporated into the bone. In this way, the vitamin also protects against weak bones and osteoporosis.

Vitamin K is good for the heart

The vitamin also ensures that calcium does not accumulate on the arterial walls, which counteracts arteriosclerosis. Put simply, this minimises the risk of cardiovascular disease and therefore leads to fewer heart attacks and strokes.

Lose weight more easily

Vitamin K is involved in several metabolic processes - energy metabolism in general as well as fat, glucose and insulin metabolism. The following question has been the subject of scientific debate for some time: Does the vitamin influence weight? This question was therefore investigated in a study involving women aged 55-65. The result: A high intake of the vitamin did indeed reduce the body weight of the women. In addition - in contrast to the women in the placebo group - external and internal abdominal fat was reduced.

Vitamin K for breast cancer

Different effects of the various forms of the vitamin have been investigated in various studies. For a long time, for example, it was assumed that all forms were functionally equivalent. However, the opposite is the case and there is debate as to whether the dietary guidelines for vitamin K should be changed. A recent study from 2019, for example, found different effects of vitamin K1 and vitamin K2 on the growth of breast cancer cells. The study came to the conclusion that vitamin K1 promotes tumours and vitamin K2 prevents tumours. This is probably due to the fact that vitamin K2 suppresses cell growth and energy metabolism. The effect of vitamin K1 and K2 has not yet been investigated in normal breast tissue, so there is still a need for further research in this area.

Foods rich in vitamin K

Vitamin K1 is found in green leafy vegetables, in case you've remembered. Don't like leafy greens? Don't worry, because you can find the vitamin in a whole range of foods.

Note: Below you will find vitamin K-rich foods. These are sorted from very rich in vitamin K to slightly less rich in vitamin K. None of the foods are better or worse because of this. It is more important that you eat as varied a diet as possible and consume all nutrients. You can find out what these are in Basic knowledge of macro and micronutrients 


Pulses and nuts

  • Fermented soya bean products
  • Raw kidney beans
  • Green beans
  • Peas
  • Chickpeas

Vegetables and other herbs

  • Matcha
  • Kale
  • Parsley
  • Spinach
  • Broccoli
  • Rosy cabbage
  • Cucumber


  • Soybean oil
  • Vegetable blend oils
  • Rape seed oil

Vitamin K supplementation

A deficiency of the vitamin is relatively rare unless you suffer from constant bruising and gastrointestinal bleeding or are a chronic alcoholic. It is much more important not to supplement the vitamin when taking Marcumar (anticoagulant), as it weakens the effect of the medication and, in the worst case, can lead to thrombosis. If you are not taking Marcumar, taking vitamin K can help to alleviate your menstrual cramps and maintain a strong heart and bones as you get older. Vitamin K is also contained in our Vitamin D3 + K2 Depot Tablets or in our O3-D3-K2 Tablets. You can read why such a combination preparation makes sense here



Beaudin et al. Oncotarget: Divergent effects of vitamins K1 and K2 on triple negative breast cancer cells. 2019; 10(23): 2292-2305.

Knapen et al. European Journal of Clinical Nutritionvolume 72: Vitamins and plant ingredients; Vitamin K-induced effects on body fat and weight: results from a 3-year vitamin K2 intervention study. 2018; 136-141.

Adams et al. American Journal of Health-System Pharmacy: Vitamin K in the treatment and prevention of osteoporosis and arterial calcification. 2005; 1574-1581.

University of Maryland: Vitamin K. 2018.

Bryk et al. Vascular Pharmacology: Heavy menstrual bleeding in women treated with rivaroxaban and vitamin K antagonists and the risk of recurrent venous thromboembolism. 2016; 242-247.