Although vitamin K2 is absolutely essential for maintaining healthy bones and blood vessels and the overall balance of calcium metabolism, it still remains in the shadow of better-known nutrients and is often overlooked, not only by the public but also in official health recommendations. Given its key role in preventing osteoporosis and cardiovascular disease, vitamin K2 deserves much more attention, both as part of an individual approach to health and in the development of dietary recommendations and prevention strategies.
What will you learn in this article?
- What is vitamin K2
- Effects of vitamin K2
- Why is vitamin K2 missing from the modern diet?
- How can I tell if I am deficient in vitamin K2?
- How and when to take vitamin K2?
- How much vitamin K2 per day?
- Vitamin K2 overdose
- Conclusion
- Key takeaways
What is vitamin K2
Vitamin K2 (menaquinone) is one of the fat-soluble vitamins and is a key member of the vitamin K family. While the better-known vitamin K1 (phylloquinone) is found mainly in green leafy vegetables and serves primarily for proper blood clotting in the liver, vitamin K2 has different functions in the body.
Vitamin K2 exists in several forms, the most important of which are MK-4 and MK-7:
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K2 MK-4: Comes mainly from animal sources (liver, eggs, meat), but is broken down very quickly in the body. To maintain a stable level, it needs to be consumed several times a day.
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K2 MK-7: Comes from fermented foods (for example the traditional Japanese dish natto or aged cheeses). It has a significantly longer half-life in the human body (up to 72 hours), which ensures a stable level in the bloodstream. In supplements, the MK-7 form (ideally in a pure all-trans configuration) is therefore considered the most effective and most bioavailable.
Effects of vitamin K2
While vitamin K1 is primarily involved in blood clotting (activating clotting factors in the liver), vitamin K2 acts in the body as a "navigator" for calcium. It activates specific proteins that make sure calcium gets exactly where it is useful and is not deposited where it can do harm.
The main effects of vitamin K2 include:
Maintaining healthy bones and teeth
Vitamin K2 activates the protein osteocalcin, which helps incorporate calcium into bones and tooth enamel. Vitamin K2 therefore supports bone strength and density and helps reduce the risk of osteopenia or osteoporosis. [2] [3]
Protecting the heart and blood vessels
Vitamin K2 helps keep blood vessels healthy by activating (carboxylating) Matrix Gla Protein (MGP), which prevents calcium from depositing in the walls of blood vessels. Vitamin K2 therefore helps keep blood vessels flexible, prevents the build-up of atherogenic plaques and the development of atherosclerosis (hardening of the arteries), and thus also the development of heart disease. [1] [2]
Cardiovascular diseases, such as myocardial infarction, stroke and heart failure, are the leading cause of death worldwide and in Europe. The main risk factors for heart disease include atherosclerosis and vascular calcification.
Supporting cell health
It activates the Gas6 protein, which protects cells (especially in the nervous system) from oxidative stress, neuroinflammation and premature cell death (apoptosis). It also contributes to protecting the mitochondria (the cells' power plants). [4]
Synergy with vitamin D3
Vitamin D3 increases the absorption of calcium from food into the blood, while vitamin K2 ensures its proper distribution from the blood into the bones. Taken together, they form an indispensable pair for overall health.
Why is vitamin K2 missing from the modern diet?
Vitamin K1 is found in plant foods, especially green leafy vegetables, and getting enough of it from the diet is not a problem for most people. The situation with vitamin K2 is different, however. Part of our vitamin K2 comes from production by our gut microbiome. In the past, a healthy gut microbiome could cover roughly half of the required vitamin K2. Today, with changes in lifestyle, eating habits and therefore the microbial diversity of the current population, it is estimated that our own vitamin K2 production covers only about 10%.
Natural sources of vitamin K2 are very limited in the diet. The richest source of vitamin K2 is natto, a traditional Japanese dish made from fermented soybeans. Natto contains vitamin K2 in its biologically active MK-7 form, which stays in the blood for several days and ensures high bioavailability. One 100 g serving of natto per week will therefore cover the required dose of vitamin K2.
Other sources are meat, dairy products and eggs from free-range animals (of grass-fed quality), which unfortunately are hard to come by. They contain the MK-4 form, which has a shorter half-life, so to maintain a sustainable vitamin K2 level you would need to eat them about twice a day.
How can I tell if I am deficient in vitamin K2?
Vitamin K2 deficiency may show up as more frequent bleeding (for example nosebleeds), a tendency to bruise, heavier menstrual bleeding in women or slower wound healing. A vitamin K2 deficiency may not be noticeable at all for a long time, but its effects can appear over time as hidden weakening of bone tissue and damage to blood vessels.
How and when to take vitamin K2?
You can take vitamin K2 at any time of day, ideally for example in the morning with breakfast or at midday with lunch. The important thing is to build a regular daily habit of taking it.
For maximum absorption and effectiveness, it is good to follow these rules:
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With a meal containing fat: Because vitamin K2 is fat-soluble, the presence of fat is essential for its proper absorption in the digestive tract (a little is enough, e.g. a teaspoon of oil, an egg, yoghurt or nuts). D3+K2 drops in an oil base (organic MCT coconut oil) make absorption easier.
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Combine with vitamin D3: As already mentioned, these two vitamins work synergistically. Supplementing vitamin D3 alone without enough K2 can lead to higher calcium levels in the blood without it being effectively deposited in the bones.
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Choose a quality form: The MK-7 form obtained by natural fermentation, for example from chickpeas or natto, in the all-trans configuration (which refers to the arrangement of atoms in the molecule) guarantees the highest biological activity in the body. This is unlike the cis configuration, which is less stable and has reduced biological activity.
How much vitamin K2 per day?
The recommended daily dose of vitamin K2 depends on age, health status and the goals of supplementation:
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Preventive daily dose for adults from around 30 years of age: Usually in the range of 80 to 120 mcg of vitamin K2. You will find a dose of 120 mcg of vitamin K2 in the product Vitamin K2 capsules.
The Daily F20 multivitamin complex contains vitamin K2 in a daily dose of 75 mcg. This amount allows it to be combined with Vitamin D3+K2 drops, which contain 25 mcg of vitamin K2 for every 1000 IU of vitamin D3. Taking Daily F20 together with Vitamin D3+K2 drops is one of the most common combinations of our products, ensuring the necessary intake of essential nutrients while allowing you to personalise your vitamin D dose to your needs.
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Adults over 50, under higher strain or for therapeutic supplementation: In cases of increased risk of bone loss (for example with osteopenia or osteoporosis), or when taking higher doses of vitamin D3, doses of 150 to 200 mcg per day are recommended after consulting a professional.
Vitamin K2 overdose
Vitamin K2 is generally considered very safe even at higher doses. There is no known toxicity associated with high doses of either vitamin K1 or vitamin K2. According to available expert recommendations, taking vitamin K2 in doses of up to 1000 micrograms (mcg) per day is considered safe for most healthy adults.
However, patients taking blood thinners from the group of vitamin K antagonists (for example warfarin) should be careful, as any increased vitamin K intake may reduce the effect of these medications. When taking anticoagulants, it is advisable to discuss vitamin K2 supplementation with your doctor.
Conclusion
Given the growing body of evidence on the importance of vitamin K2 for bone and cardiovascular health, it is time to rethink its role in our diet and health care. Its deficiency is common but overlooked, and yet it can have a major impact on quality of life. We therefore recommend paying attention to an adequate intake of vitamin K2, whether through quality foods (such as natto) or well-chosen supplementation.
Key takeaways
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Vitamins K1 and K2 have different functions: Vitamin K1 (phylloquinone) is important mainly for normal blood clotting, while vitamin K2 (menaquinone) helps the body manage calcium properly.
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Vitamin K2 supports healthy bones and teeth: It activates the protein osteocalcin, which helps incorporate calcium into bone tissue and teeth, where it is needed.
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K2 protects blood vessels from unwanted calcium deposits: Vitamin K2 activates the MGP protein, which helps prevent calcium from being deposited in the vessel walls and supports cardiovascular health.
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K2 deficiency can be fairly common: There are relatively few natural sources of vitamin K2 in the modern diet. The richest sources are natto, some fermented foods, and eggs and dairy products from pasture-raised animals.
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The best-researched form is K2 MK-7: The MK-7 form is the most bioavailable form and remains in the body for up to 72 hours.
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Adequate intake matters especially as we age: The need to support bone and vascular health grows especially after the age of 50, when the risk of osteoporosis and cardiovascular disease increases.
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Vitamin K2 and vitamin D3 make a good combination: While vitamin D supports calcium absorption, vitamin K2 helps ensure it is used where the body really needs it.
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Dosage:
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Adults (30+ years): 80–120 mcg daily
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People aged 50+: at least 150 - 200 mcg daily
- Safe dosage up to 1000 mcg daily
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Sources and studies:
The well-known Rotterdam Study from 2004 confirmed that long-term intake of vitamin K2 (at a dose of at least 32 mcg per day) reduces the risk of vascular calcification and cardiovascular disease by 50%. [1]
A 2015 clinical study found that postmenopausal women experienced improved arterial elasticity and reduced arterial stiffness after three years of daily vitamin K2 supplementation (at a dose of 180 mcg). [2]
[1] Geleijnse JM, Vermeer C, Grobbee DE, Schurgers LJ, Knapen MH, van der Meer IM, Hofman A, Witteman JC. Dietary intake of menaquinone is associated with a reduced risk of coronary heart disease: the Rotterdam Study. J Nutr. 2004 Nov;134(11):3100-5. doi: 10.1093/jn/134.11.3100. PMID: 15514282. The Journal of Nutrition.
[2] Knapen MH, Braam LA, Drummen NE, Bekers O, Hoeks AP, Vermeer C. Menaquinone-7 supplementation improves arterial stiffness in healthy postmenopausal women. A double-blind randomised clinical trial. Thromb Haemost. 2015 May;113(5):1135-44. doi: 10.1160/TH14-08-0675. Epub 2015 Feb 19. PMID: 25694037. Thieme: Thrombosis and Haemostasis.
[3] Maresz K. Proper Calcium Use: Vitamin K2 as a Promoter of Bone and Cardiovascular Health. Integr Med (Encinitas). 2015 Feb;14(1):34-9. PMID: 26770129; PMCID: PMC4566462.
[4] Yan Q, Zhang T, O'Connor C, Barlow JW, Walsh J, Scalabrino G, Xu F, Sheridan H. The biological responses of vitamin K2: A comprehensive review. Food Sci Nutr. 2023 Jan 6;11(4):1634-1656. doi: 10.1002/fsn3.3213. Erratum in: Food Sci Nutr. 2025 Jan 27;13(1):e70005. doi: 10.1002/fsn3.70005. PMID: 37051359; PMCID: PMC10084986.
