At a glance
A fat-soluble vitamin that enables blood clotting and directs calcium into the bones.
In Vykea: menaquinone-7 (MK-7), 12 to 24 µg per daily dose depending on the product.
Anyone taking anticoagulant medication may only change their vitamin K intake after consulting a doctor.

Vitamin K is a fat-soluble vitamin. The letter K derives from the word Koagulation (coagulation) and refers to what is probably the vitamin's best-known task: its role in blood clotting. Vitamin K is also involved in activating proteins that bind calcium in the bones, and so contributes to the maintenance of normal bones. The collective term vitamin K covers several related compounds, of which vitamin K1 (phylloquinone) and the menaquinones, which belong to the vitamin K2 group, are the most important. In our products we use menaquinone-7 (MK-7), a natural form from the vitamin K2 group. This entry explains the forms, food sources, functions, requirements, laboratory testing, possible signs of deficiency and interactions of vitamin K2.

Vitamin K occurs in several natural and synthetic forms. Vitamin K1 (phylloquinone) is produced by plants and is found mainly in green leafy vegetables. Vitamin K2 is the umbrella term for the menaquinones, a group of compounds that differ in the length of their side chain and are designated MK followed by a number, such as MK-4 or MK-7. Menaquinones are produced by bacteria, including microorganisms in fermented foods and the gut flora. A third, synthetic form is vitamin K3 (menadione), which plays no role in human nutrition.

The individual forms differ in how they behave in the body. Compared with vitamin K1, menaquinone-7 (MK-7) is well absorbed and remains measurable in the blood for a longer time after absorption. This comparatively long residence time (half-life) is a property of the substance and not a statement about a superior health effect. Because vitamin K is fat-soluble, it is absorbed in the gut together with dietary fats; bile acids and digestive enzymes from the pancreas are needed for its absorption. It is therefore better utilised when taken with a meal containing fat. Our products use menaquinone-7 (MK-7).

Vitamin K1 is found mainly in green vegetables such as kale, spinach, chard, broccoli, Brussels sprouts and lettuce, as well as in vegetable oils. It provides most of the vitamin K taken in from food. Vitamin K2 (menaquinones), by contrast, occurs mainly in animal and fermented foods, such as meat, some types of cheese and eggs. A particularly rich source of MK-7 is natto, a traditional Japanese dish made from fermented soya beans. In addition, the gut flora produces menaquinones, although their contribution to vitamin K status is difficult to quantify.

Vitamin K is relatively stable during normal food preparation and is sensitive mainly to light. The body's stores are limited and, by calculation, last only for about one to two weeks. Regular intake is therefore important.

Vitamin K acts as a cofactor for the enzyme that activates certain proteins in the body. This activation takes place by attaching a chemical group (gamma-carboxylation) to what are known as Gla proteins. Only in this activated form can the proteins bind calcium and perform their task:

The next section shows which of these functions are authorised as health claims.

The following health claims are authorised for vitamin K in the EU:

These claims apply to vitamin K in general and therefore also to the form used in our products, menaquinone-7 (MK-7).

For vitamin K, no exact recommended intakes can be derived from the available data. The German Nutrition Society (DGE) therefore gives estimated values for an adequate intake. The following values are taken from the D-A-CH reference values.

The nutrient reference value for labelling (NRV) is 75 µg per day. The European Food Safety Authority (EFSA) has likewise not derived exact recommended intakes for vitamin K, but only Adequate Intake values, based on phylloquinone (vitamin K1). EFSA has not set a tolerable upper intake level for vitamin K, as the available data were insufficient to do so. The assessment described no adverse effects for vitamin K from usual sources.

A higher risk of inadequate vitamin K status exists mainly when absorption from the gut is impaired. This includes chronic inflammatory bowel disease, impaired bile flow, liver diseases such as cirrhosis of the liver, and pancreatic insufficiency, because vitamin K, as a fat-soluble vitamin, depends on bile acids and digestive enzymes. A very low intake of green vegetables can also reduce the supply of vitamin K1.

Newborns are regarded as a group requiring particular attention, because their vitamin K stores are low at birth and their gut colonisation is not yet established. In Germany, it is therefore standard practice to give vitamin K under medical supervision as part of the routine check-ups for newborns. Certain medicines can also affect vitamin K status (see the Interactions section).

Through the activation of matrix Gla protein, vitamin K is involved in regulating where calcium is deposited in the body. In scientific discussion, inadequate vitamin K status is associated with increased, unwanted calcification of vessel walls, while calcium is needed for the bones at the same time. Several studies address the question of whether an adequate vitamin K2 supply influences this process. These are scientific relationships at research level and not a promise of effect for any individual product. Unlike for bones, no health claim relating to the cardiovascular system or blood vessels is authorised for vitamin K in the EU. Whether vitamin K intake is advisable in an individual case is best clarified with a doctor.

Assessing vitamin K status is more demanding than for many other vitamins. The direct vitamin K level in the blood (serum or plasma, measured after fasting) fluctuates widely and mainly reflects intake over the last few hours. The proportion of non-activated (undercarboxylated) osteocalcin, determined using a special laboratory method, is regarded as a more sensitive marker of longer-term status. With regard to clotting, a prolonged clotting time can indicate a marked shortfall in supply, but it is a non-specific finding.

Elevated proportions of non-activated Gla proteins suggest a marginal supply.

Note: Choosing the appropriate parameter, interpreting the values and any supplementation should be left to a doctor, especially if anticoagulant medication is being taken.

Pronounced vitamin K deficiency is rare in adults. When it occurs, it affects blood clotting first. Possible signs are an increased tendency to bleed, such as more frequent nosebleeds, bruising easily (haematomas) or a prolonged clotting time. Because vitamin K is also involved in bone metabolism, research associates a longer-lasting marginal vitamin K status with reduced bone density.

Such signs are not conclusive and can have many causes.

Note: You should always have an increased tendency to bleed investigated by a doctor. Diagnosis and deciding on any treatment should be left to a doctor.

The following information summarises the areas of use described in the specialist literature.

Note: It does not replace medical advice; targeted or higher-dose use should be left to a doctor.

Important: these doses are not a general recommendation. The amounts of vitamin K2 in our products are geared to an adequate supply in terms of the nutrient reference value (NRV), not to the higher research doses cited in individual studies.

Note: Anyone taking anticoagulant medication must not change their vitamin K intake on their own, but must check with a doctor beforehand (see the special note in the following section).

Certain anticoagulant medicines act as vitamin K antagonists by inhibiting the activation of the vitamin K-dependent clotting factors. These include coumarin-type active ingredients such as phenprocoumon (for example Marcumar) and warfarin. Additional vitamin K intake can weaken the effect of these medicines and alter carefully adjusted clotting.

Note: If you take such a medicine, you must not use a product containing vitamin K without consultation, and it is essential that you check the intake with a doctor beforehand. This also applies to the amount of vitamin K2 contained in our products.

Prolonged treatment with antibiotics can reduce the production of menaquinones by the gut flora. With permanently impaired fat digestion or with conditions that impair the absorption of fat-soluble vitamins, vitamin K absorption can also suffer. In rare cases, very high doses of vitamin E can affect the action of vitamin K.

Note: If you take medicines regularly, you should discuss additional vitamin K intake with a doctor beforehand.

Vitamin K2 and vitamin D3 act at neighbouring points in calcium metabolism and complement each other there. From the perspective of vitamin K2, this interplay can be described as follows: vitamin D3 promotes the absorption of calcium from the gut and contributes to normal blood calcium levels. For this calcium to reach the right place, the vitamin K-dependent Gla proteins are needed, and these can only work once they have been activated by vitamin K2. The well-studied menaquinone-7 (MK-7) activates two of these proteins, among others: osteocalcin binds calcium into the bone structure, while matrix Gla protein in the vessel walls helps to limit unwanted calcium deposits.

The scientific literature interprets this relationship as meaning that, without an adequate vitamin K2 supply, the calcium absorbed through the action of vitamin D3 lacks direction: if the Gla proteins remain insufficiently activated (undercarboxylated), this is associated with lower incorporation of calcium into the bones and with increased calcification of soft tissues. Reviews therefore describe that a combined supply of both vitamins can be more favourable for bone health than an intake of either one alone. Menaquinone-7 is particularly well suited to this task because it is well absorbed and has a comparatively long half-life, meaning it remains available in the blood for longer.

Because of these complementary roles, vitamin K2 and vitamin D3 are often considered together in research, which explains the combination in our products D3K2 Instant and D3K2 Drops. You can find more about the function, requirements and testing of the partner nutrient in the Vitamin D3 entry. The classification described here reflects general, referenced findings from nutritional science and is not a promise of effect for any individual product. For the health claims authorised under EU law, only the nutrient-specific wordings in the section above apply.

Vitamin K2 (menaquinone-7) is contained in several of our products:

The % of NRV is based on the labelling value of 75 µg per day. Because vitamin K is fat-soluble, we recommend taking it with a meal containing fat to support absorption. In D3K2 Instant and D3K2 Drops, vitamin K2 is combined with vitamin D3 (see the section “Why vitamin K2 and D3 belong together”).

Note: Please be sure to read the special note on anticoagulant medicines above: if you take vitamin K antagonists such as phenprocoumon or warfarin, check with a doctor before use.

Food supplements are not a substitute for a balanced, varied diet and a healthy lifestyle.

Any further questions? Our service team will be happy to help at [email protected].