Vitamin K

Vitamin K is a fat-soluble vitamin that bears the name of not just one compound, but several compounds with a similar structure and function. Individual compounds of vitamin K are called vitameres, and they differ in the length and saturation of the side chain in the structure.

Among the most important is vitamin K1 or phylloquinone, which is found mainly in green vegetables. Vitamins K2 or menaquinones are compounds produced by bacteria of the digestive flora, the best known being menaquinone-4 (MK-4) and menaquinone-7 (MK-7). In addition to bacteria, the source of vitamin K2 is also a food of animal origin, such as eggs, fish, and meat, as well as bacterial fermented food, which includes yogurts and cheeses. The third group of vitamins is vitamin K3 or menadione, which is of synthetic origin and does not occur in nature, it is used mainly in animal feed.

Because vitamin K is only synthesized by plants and bacteria, it must be taken into the body through food. Its function in the body is, in addition to activating proteins necessary for blood clotting, also preventing calcification of arteries and other soft tissues, regulating cell division and differentiation, and promoting bone mineralization.

The European Food Safety Authority (EFSA) has approved the following claims for vitamin K:

  • Contributes to normal blood clotting
  • Contributes to maintaining healthy bones

The daily intake of vitamin K in adults is 1 µg / kg body weight and does not differ from gender, and the same applies during pregnancy and lactation. It is around 70 µg / day for an adult and 45 µg or 65 µg / day for teenagers aged 11 to 17. Vitamin K is similarly absorbed in the gut as other lipids. Compared to vitamin C, which is regularly excreted from the body, vitamin K remains in the body, mostly in the liver, which is the primary storage organ.

Green leafy vegetables are very rich in vitamin K. Among all, spinach wins, followed by kale, white cabbage, soybeans… You can see more in the table



Vitamin K content per 100g of food (mg)

Recommended Dietary

Allowances (RDA) in %































Edam cheese



Fresh cheese







 Japanese traditional dish called natto is by far the richest source of MK-7 or. vitamin K2. 100g of food contains as much as 1098 µg of vitamin K2. Natto is a gram-positive bacterium called Bacillus subtilis var. natto fermented soy, which in Japan is most commonly used for breakfast.

Some suggestions of our lunches that were very rich in vitamin K.

As we have already written, vitamin K is very lipophilic, which means that it binds to fats. Studies have shown that the absorption of vitamin K1 is poorer in fresh vegetables. In the case of spinach, e.g. found that despite being very rich in vitamin K1, vitamin absorption was only 4.1% in an otherwise small group of healthy volunteers. When spinach was added to the butter, however, the absorption reached 13.3%. We need to know that the latter result in a seemingly low percentage still means more than 60 µg of vitamin K1 per 100 g of spinach, which is almost the amount of the recommended daily intake of the vitamin!

Slightly better absorption is with vitamin K2, which is found mainly in foods of animal origin but is much less quantitatively in individual foods. Vitamin K is also produced by aerobic gram-positive and anaerobic bacteria in the intestinal flora, but here the limiting factor here is the absence of bile salts in the colon, which are necessary for the absorption of vitamin K2.

It is also good to know that heat treatment of foods such as cooking and baking does not affect the stability of the vitamin, and with freezing, vitamin K is lost.

According to the studies known so far, in which prolonged high doses were used, no adverse effects were observed.

There are several reasons for vitamin K deficiency. They can be primary if we do not get enough vitamins in the body through food. Secondary causes of deficiency are: eating a diet low in fat, impaired fat absorption, imbalance in the intestinal flora, anticoagulant therapy, or insufficient passage of vitamin K across the placenta.

The main signs of vitamin K deficiency are coagulopathies, which are manifested by prolonged blood clotting time and hypoprothrombinemia, ie a reduced amount of blood proteins. Low vitamin levels have also been linked in research to an increased risk of osteoporosis, cartilage fractures and injuries, and osteoarthritis. The risk is even higher in the elderly and patients with chronic kidney disease.

Due to poor placental transfer of vitamin K, insufficient vitamin content in breast milk, and sterile gut without bacteria for several days after birth, newborns have an increased risk of vitamin K deficiency. Vitamin K preparations received in newborns are used in clinical practice to prevent deficiency. immediately after birth, after the first breastfeeding, a few days later, and a month later if the baby is just breastfed.