Vitamin K2 MK-7 – D3’s partner in calcium metabolism
How does vitamin K2 MK-7 differ from the MK-4 form, and why is it increasingly recommended to combine it with vitamin D3? Find out what role it plays in the body, how to dose it correctly, and what sources it comes from.
Vitamin K2 belongs to the group of fat-soluble vitamins and is one of the two main subtypes of vitamin K (the other being K1 – phylloquinone, found mainly in green vegetables). Within K2 itself, there are several forms, designated by the abbreviation MK (from menaquinone) and a number indicating the length of the side chain. The most commonly discussed are MK-4 and MK-7, with the latter having gained particular popularity in recent years. Vitamin K contributes to normal blood clotting and to the maintenance of normal bones – these are two statements approved by the European Food Safety Authority that best reflect its role in the body. For those concerned with preventive healthcare in middle age, this is a nutrient particularly worth paying attention to.
What is vitamin K2 MK-7 and where does it come from?
Vitamin K2 MK-7 (menaquinone-7) is a long-chain form of menaquinone, naturally produced through bacterial fermentation. The richest natural source of K2 MK-7 is natto – a traditional Japanese dish made from fermented soya beans. During fermentation, the bacterium Bacillus subtilis natto produces significant amounts of menaquinone-7, making natto a unique dietary source of this vitamin. K2 is also present in smaller quantities in certain mature cheeses and meat, but its intake in a typical European diet tends to be low.
The MK-7 form is characterised by a long half-life in the body – it remains in the blood for up to 72 hours, whilst MK-4 disappears from the bloodstream within a few hours. For this reason, MK-7 is often the preferred form for daily, single-dose supplementation.
The role of vitamin K2 in the body – blood clotting and bone health
Vitamin K acts as a cofactor for the enzyme responsible for the carboxylation of specific proteins – that is, the process by which these proteins become functionally active. The two most important areas of action are: contributing to normal blood clotting (through the activation of clotting factors) and contributing to the maintenance of normal bone health (through the activation of the protein osteocalcin, which plays a role in bone mineralisation).
It is precisely from the role of K2 in the activation of osteocalcin and another protein – MGP (Matrix Gla Protein) – that the popular theory arose that vitamin K2 ‘directs’ calcium to the bones. This is a simplification, but it captures the idea well: the active forms of both these proteins help ensure the proper utilisation of calcium in the body. You can find out more about calcium itself and calcium supplementation in the article Calcium – is supplementation suitable for everyone?.
Why K2 and D3 are combined in a single preparation
Vitamin D3 and vitamin K2 are a frequently recommended supplement combination – and for good reason. Vitamin D3 contributes to the proper absorption of calcium, which means it helps to ‘draw’ it from the digestive tract into the bloodstream. Vitamin K2, in turn, activates the proteins responsible for the proper utilisation of this calcium, including its incorporation into bone tissue. To put it simply: D3 helps the body absorb calcium, whilst K2 supports its proper distribution.
Many people already take vitamin D3 (particularly during the autumn and winter months) and the question naturally arises as to whether to supplement this with K2. You can find a more comprehensive overview of this combination in the article How to use vitamins K2 and D3.
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K2 MK-7 vs K2 MK-4 – which form to choose
The most frequently asked question concerns the choice between the two forms of menaquinone. Both – MK-4 and MK-7 – are active forms of vitamin K2, but they differ in their pharmacokinetics and the typical doses used in supplements.
MK-4 has a short half-life in the body – it disappears from the bloodstream within a few hours of ingestion. For this reason, MK-4 supplements are usually taken in higher doses (45 mg per day, divided into 3 doses). MK-7 persists in the blood for much longer, allowing for a single daily dose of significantly lower amounts – typically 75–200 mcg per day. For anyone looking for a convenient, daily supplement, a single MK-7 capsule or drop is simply a more practical solution.
Vitamin K2 MK-7 dosage – how much per day
A typical serving of vitamin K2 MK-7 in dietary supplements ranges from 75 to 200 mcg per day. Lower doses (75–100 mcg) are suitable as a supplement to the daily diet, whilst higher doses (150–200 mcg) are often chosen by adults who combine K2 supplementation with higher doses of vitamin D3.
Vitamin K2 MK-7 is best taken with a meal containing fats – as a fat-soluble vitamin, it is then better absorbed. The time of day is not crucial, but many people choose to take it at breakfast or lunch. The droplet form allows for convenient and precise dosing, whilst combined preparations with D3 make daily supplementation with a single product easier.
[tip:Vitamins K2 and D3 are a classic supplement pairing. If you are already taking vitamin D3, consider adding K2 MK-7 – both work together to regulate the body’s calcium metabolism. You’ll find the full range in our Vitamins category.]
Safety and contraindications
Vitamin K2 MK-7, in doses typical for dietary supplements, is well tolerated by adults. The most important contraindication applies to people taking anticoagulants from the group of vitamin K antagonists (e.g. warfarin, acenocoumarol). The mechanism of action of these medicines is precisely to block the activity of vitamin K, so supplementation with vitamin K may reduce their therapeutic effect.
[warning:If you are taking anticoagulants (warfarin, acenocoumarol, Sintrom), you must consult your doctor before taking vitamin K2 supplements. Vitamin K affects the action of these medicines and requires monitoring of the INR. Self-medication with supplements may interfere with your anticoagulant therapy.]
Who will find K2 MK-7 particularly beneficial
Vitamin K2 MK-7 is a nutrient of particular interest to adults who are mindful of their bone health. The natural dietary intake of K2 can be low, particularly among those who do not eat natto or mature cheeses on a regular basis. Supplementation can therefore be a sensible addition to the daily diet – particularly for those already taking vitamin D3.
From the perspective of preventative healthcare in middle age, K2 MK-7 fits well into a broader range of bone-supporting nutrients – alongside vitamin D3, calcium and magnesium. Those interested in comprehensive vitamin supplementation will find a wider range of products in the Vitamins and Minerals categories.
Summary: Vitamin K2 MK-7 is a long-chain form of menaquinone, which contributes to normal blood clotting and the maintenance of normal bones. Its long half-life allows for convenient, once-daily dosing, typically 75–200 mcg per day. Combining K2 MK-7 with vitamin D3 is physiologically justified – both vitamins work together in calcium metabolism. The most important contraindication is the use of anticoagulants, which requires consultation with a doctor.