Vitamin K2 MK-7: what is really known and what is a myth about D3

Most adult Poles take vitamin D3 in winter, and increasingly often together with vitamin K2 MK-7. The justification has been circulating on the internet for years and always sounds the same: without K2, calcium released by D3 will deposit in the arteries instead of in the bones. We checked what this claim is based on. We reviewed interventional studies in humans, a meta-analysis with over 83,000 participants, and current Polish guidelines for vitamin D supplementation. The popular thesis does not hold up. Below you will find what can be supported by data: what vitamin K2 does in the body, how MK-7 differs from MK-4, how much food provides, and who should not use it under any circumstances.

KEY INFORMATION
• Vitamin D supplementation did not increase the number of cardiovascular events in a meta-analysis of 21 randomized studies with 83,291 participants (Barbarawi et al., JAMA Cardiology 2019).
• In the AVADEC study, 720 µg MK-7 with vitamin D for 24 months did not slow down calcification of the valve or coronary arteries (Diederichsen et al., Circulation 2022).
• Polish guidelines for vitamin D supplementation from 2023 do not mention vitamin K2 even once.
• Warfarin and acenocoumarol are absolute contraindications for K2 supplements.

Does vitamin D3 without vitamin K2 really harm the arteries?

There is no evidence for this in humans. No interventional study has been published in which vitamin D3 at recommended doses, given without K2, would increase arterial calcification or the number of heart attacks. The largest available compilation includes 21 randomized studies with 83,291 participants, and no difference is seen in any endpoint.

In this meta-analysis, the risk of serious cardiovascular events was 1.00 (95% CI 0.95-1.06), heart attack 1.00, stroke 1.06, cardiovascular death 0.98, and death from any cause 0.97 (Barbarawi i in., JAMA Cardiology 2019). The results were consistent regardless of the dose of vitamin D, the method of administration, and whether patients were simultaneously receiving calcium. The authors checked these factors in subgroups, not the presence of menaquinone, so the meta-analysis does not say anything about whether adding vitamin K2 would have made a difference.

A more direct point: in the Women’s Health Initiative sub-study, 754 women took 1000 mg of calcium with 400 IU of vitamin D3 or placebo for an average of 7 years, after which coronary artery calcification was measured tomographically. The average score was 91.6 compared to 100.5 in the placebo group, with no statistical difference (Manson i in., Menopause 2010). The doses were moderate, and no one studied 10,000 IU daily in this way, so the lack of evidence of harm is not the same as evidence of safety at every dose. But the claim circulating on the internet goes much further: it speaks of harm that has been demonstrated. It has not.

What did the study show when K2 was given together with vitamin D?

It did not slow down vascular calcification. In the multicenter AVADEC trial, 365 men with an average age of 71, with advanced calcification of the aortic valve, were randomly assigned to 720 µg MK-7 with 25 µg of vitamin D daily or to placebo for 24 months. The increase in calcification score was 275 units in the intervention group and 292 in the placebo group.

The difference of 17 units was not significant (p=0.64), nor were the changes in valve surface area and flow velocity. The progression of calcification in the aorta and coronary arteries also did not differ, nor did the number of valve surgeries, deaths, and cardiovascular events (Diederichsen i in., Circulation 2022). However, the most interesting detail is the biochemical aspect: the concentration of the inactive form of MGP protein decreased by 212 pmol/l in the MK-7 group, while in the placebo group it increased by 45. The biomarker acted exactly as the theory predicts. Calcification did not budge.

Coronary artery analysis in 304 participants without ischemic disease showed the same picture: an increase in score of 203 versus 254 units, p=0.089, which is a neutral result (Hasific i in., JACC Advances 2023). Two secondary outcomes were favorable: in the subgroup with initially the highest calcification, the difference exceeded the significance threshold, and safety events were less frequent in the supplementation group. The authors themselves describe both as hypotheses to be tested, not as conclusions. The caveat is fair: AVADEC compared MK-7 with vitamin D against placebo, not D3 alone against D3 with K2. However, it directly examined the mechanism on which the entire popular thesis is based.

Do Polish guidelines for vitamin D supplementation require vitamin K2?

No. The update of Polish recommendations from 2023 does not mention vitamin K2, menaquinone, or MK-7 even once throughout the document. It describes doses of cholecalciferol according to age and body weight, principles for measuring 25(OH)D in at-risk groups, and upper safety limits.

The document was created under the editorship of Paweł Płudowski with a team of several dozen Polish scientific societies and was published in the journal Nutrients (Płudowski et al., 2023). A person who follows it and does not take K2 is not doing anything against the recommendations. If a supplement manufacturer presents vitamin K2 as a condition for the safety of vitamin D, it is not a quote from the guidelines.

It is important to distinguish two things, as they can be confused. The European Food Safety Authority has allowed a health claim regarding the role of vitamin K in maintaining proper bone status, which is cited by producers; the authors of the cited study on MK-7 also remind of this. The claim pertains to bones, not arteries, and does not mention interaction with vitamin D3. We do not provide doses here as recommendations: it is the doctor or pharmacist who determines them based on the result of 25(OH)D and the medications taken. If you are looking for context for supplementation after fifty, we have described it in the post about supplements for sarcopenia in seniors.

What does vitamin K2 actually do in the body?

It activates vitamin K-dependent proteins. Vitamin K is a cofactor for gamma-glutamyl carboxylase, an enzyme that adds a carboxyl group to glutamic acid residues in these proteins. Without this reaction, osteocalcin in bones and MGP protein in blood vessel walls remain inactive and do not bind calcium ions.

MGP, or Matrix Gla Protein, is the strongest known inhibitor of calcium deposition in blood vessels. Its inactive form, denoted as dp-ucMGP, serves as a laboratory indicator of low vitamin K supply. This biochemistry is well documented and no one disputes it. The problem lies one level higher, where the indicator transitions to patient health.

In the prospective EPIC-NL study, dp-ucMGP was measured in baseline samples and participants were followed for an average of 11.5 years. 1154 cases of coronary heart disease and 380 strokes were collected. The concentration of inactive MGP was not associated with the risk of coronary heart disease (HR per standard deviation 1.00; 95% CI 0.93-1.07) or stroke (HR 0.98) after adjusting for risk factors (Dalmeijer i in., Journal of Thrombosis and Haemostasis 2014). The authors stated directly that they did not confirm the association. The mechanism exists, but the causal chain to heart attack remains unclosed.

What is the difference between MK-7 and MK-4?

The length of the side chain, and in practice whether it even reaches the blood in a dose from the supplement. A direct comparison was made by Sato and colleagues in healthy Japanese women: after a single dose of 420 µg MK-7, the serum concentration peaked after six hours and was still detectable after 48, while MK-4 did not appear in the serum in any subject at any measurement point.

Seven days of taking 60 µg resulted in the same discrepancy: MK-7 concentration significantly increased in all, while MK-4 did not increase at all. The authors conclude that MK-4 present in food does not raise vitamin K levels measured by serum concentration (Sato i in., Nutrition Journal 2012). Separately, it was measured how MK-7 behaves with longer use: it accumulates to concentrations seven to eight times higher, provides more stable serum concentrations, and more fully carboxylates osteocalcin than synthetic vitamin K1 (Schurgers i in., Blood 2007).

This does not mean that MK-4 is useless, only that in the amounts found in supplements it does not raise vitamin K levels in the blood. In the Japanese osteoporosis treatment guidelines from 2011, menatetrenone, or MK-4, is listed at a dose of 45 mg per day (Orimo i in., Archives of Osteoporosis 2012). This is a quantity hundreds of times greater than a typical drugstore capsule, so those results cannot be transferred to it.

Does vitamin K2 strengthen bones?

The data is ambiguous. In a three-year randomized study involving 244 healthy postmenopausal women, a daily dose of 180 µg MK-7 improved vitamin K status and slowed the age-related decline in lumbar spine and hip bone mineral density. There was no effect on the total hip.

To badanie (Knapen i in., Osteoporosis International 2013) is the most frequently cited argument for MK-7. The same group of participants was used to assess arterial stiffness, where after three years, pulse wave velocity decreased, and inactive MGP halved (Knapen i in., Thrombosis and Haemostasis 2015). The vascular outcome therefore comes from a separate publication from 2015, although it is sometimes attributed to a 2013 study. The product was the commercial MenaQ7, explicitly named in the publication, and both studies as well as the above-mentioned comparison of K1 with MK-7 have common authors. AVADEC, with a hard endpoint and an independent team, weighs more in this comparison.

A broader picture is provided by a review of 36 randomized studies. In postmenopausal women and individuals with osteoporosis, the chance of clinical fracture was lower in the vitamin K groups (OR 0.72; 95% CI 0.55-0.95), but after restricting the analysis to studies with low risk of error, the advantage disappeared (OR 0.76; 95% CI 0.58-1.01). No effect was found on vertebral fractures and bone density, and the authors concluded that the evidence is insufficient (Mott i in., Osteoporosis International 2019). The review itself was created partly because the reliability of some earlier evidence in this area has been questioned. You can find more about supplementation during the perimenopausal period in the post about suplementach dla kobiet po 40.

Who should not use vitamin K2?

Individuals taking warfarin or acenocoumarol. These medications work by blocking the vitamin K epoxide reductase, the enzyme that regenerates its active form. Vitamin K2 supplementation provides vitamin K bypassing this enzyme, lowers INR, and negates anticoagulant protection. This is an absolute contraindication and the most important information in this entire text.

This is not a theoretical warning and has a specified magnitude. The authors of the comparison of K1 with MK-7 conclude their work with a note directed at hematologists: preparations providing 50 µg MK-7 daily or more may significantly clinically interfere with the treatment of oral anticoagulants (Schurgers i in., Blood 2007). A typical drugstore capsule falls within this range or exceeds it.

In practice, this means a ban on self-administering any vitamin K preparation, including multivitamins where K2 may be hidden in the composition. If the anticoagulation physician decides otherwise, the condition is a constant daily dose and more frequent INR monitoring. Fluctuations in vitamin K intake are a classic cause of result variations and loss of control over treatment.

Newer generation medications behave differently. Dabigatran inhibits thrombin, while rivaroxaban, apixaban, and edoxaban block factor Xa; none of them utilize the vitamin K pathway. This type of interaction does not apply to them, but it does not exempt from informing the doctor about any supplement. A separate note concerns absorption: vitamin K2 is fat-soluble, so orlistat and cholestyramine limit its absorption, while a meal with fat improves it. Pregnant and breastfeeding women, as well as chronically treated individuals, should discuss supplementation with their doctor before starting.

How much vitamin K2 does food provide?

Definitely the most natto, Japanese soy fermented by Bacillus subtilis. In a nutritional experiment, six healthy volunteers ate either 400 g of spinach or 200 g of natto; after natto, the concentration of vitamin K2 in the blood was about ten times higher than the concentration of K1 after spinach. Besides natto, menaquinones are found in meat, liver, butter, egg yolk, and aged cheeses.

The content base of both vitamins in food was established by Schurgers and Vermeer (Haemostasis 2000), and the role of dairy and fermented foods was later summarized in a review in Advances in Nutrition; its authors note that the contribution of menaquinones to the total vitamin K intake is still poorly accounted for, although in many regions dairy is often their main source (Walther i in., 2013). It is worth noting where the entire hypothesis originated. The Rotterdam Study observed 4807 individuals from the turn of the years 1990-1993 to 2000, and in the highest tercile of menaquinone intake, the risk of coronary death was 0.43, death from any cause was 0.74, and severe aortic calcification was 0.48 compared to the lowest tercile (Geleijnse i in., Journal of Nutrition 2004). Vitamin K1 yielded nothing. Similarly, a cross-sectional study of 564 postmenopausal women showed the same results (Beulens i in., Atherosclerosis 2009). Both are observational, and menaquinones came from cheese, not capsules. People eating a lot of aged cheese differ from the rest of the population in many ways. When the same hypothesis was tested with random assignment to a supplement, the result was neutral.

Frequently Asked Questions

We have gathered questions that most often arise regarding vitamin K2 MK-7 and its comparison with vitamin D3.

Do I need to take vitamin K2 together with vitamin D3?

This is not based on any guidelines or studies in humans. The update of Polish vitamin D supplementation recommendations from 2023 does not mention vitamin K2 even once. No interventional study has been published in which vitamin D3 given without K2 would damage the vessels. Discuss the decision to combine both preparations with your doctor.

Does vitamin K2 reverse calcifications in the arteries?

The randomized study did not confirm this. In the AVADEC trial, 365 men received 720 µg MK-7 with vitamin D or placebo for 24 months. The increase in aortic valve calcification was 275 units compared to 292 in the placebo group, and the difference of 17 units was not significant (p=0.64). Calcifications of the aorta and coronary arteries also did not differ.

What is the difference between MK-7 and MK-4?

Absorption in doses found in supplements. After a single dose of 420 µg MK-7, it was detectable in the serum even after 48 hours, while MK-4 did not appear in any of the subjects (Sato et al., Nutrition Journal 2012). MK-4 has documented effects only at a drug dose of 45 mg per day.

Can vitamin K2 be used with anticoagulant medications?

With warfarin and acenocoumarol, this is an absolute contraindication. These medications block the vitamin K epoxide reductase, while the supplement provides vitamin K bypassing this enzyme, lowering INR and negating anticoagulant protection. NOAC medications, such as dabigatran, rivaroxaban, apixaban, and edoxaban, do not act through the vitamin K pathway, so this interaction does not apply to them.

Can aged cheese replace natto as a source of K2?

Not in terms of quantity. After a serving of natto, the concentration of vitamin K2 in the blood was about ten times higher than the concentration of K1 after a large serving of spinach (Schurgers and Vermeer, Haemostasis 2000). Aged cheeses and other dairy products remain the most important source of menaquinones in the European diet.

What do Polish guidelines say about vitamin K2 in D3 supplementation?

Nothing. The document by Płudowski and co-authors from 2023, published in the journal Nutrients, describes doses of cholecalciferol according to age and body weight, as well as the principles of measuring 25(OH)D. The word menaquinone, the abbreviation MK-7, or any mention of vitamin K in any form does not appear throughout the text.

You can find preparations with vitamin K2 MK-7 and sets with vitamin D3 in the section supplements in the u Bucha store.

This article is for informational and educational purposes and does not constitute medical advice. Before starting supplementation, consult your doctor, especially if you are taking medications regularly, are pregnant or breastfeeding, or have a chronic illness.

Author: Michał Waluk · Opublikowano: 2026-05-29 · Aktualizacja: 2026-08-14