Vitamin K2 — Calcium Regulation, Bones & Vascular Health
Vitamin K2 is a fat-soluble form of vitamin K involved in calcium regulation, bone metabolism, blood clotting and cellular function.
Vitamin K2 belongs to a family of compounds called menaquinones, which include forms such as MK-4 and MK-7.
One of the most important functions of vitamin K is to activate specific proteins through a process called gamma-carboxylation.
This allows these proteins to bind calcium and perform their normal biological functions.
Vitamin K2 and Calcium
One of the most important concepts surrounding vitamin K2 is calcium distribution.
Calcium is essential for strong bones and teeth, but calcium also needs to be properly regulated within soft tissues.
Vitamin K-dependent proteins help regulate where calcium is deposited and where it is prevented from accumulating.
In simple terms:
Vitamin K2 → activates calcium-regulating proteins → supports proper calcium utilisation
This is why K2 is often described as helping the body put calcium where it belongs.
Vitamin K2 and Bone Health
Vitamin K2 is involved in the activation of osteocalcin, a protein produced by bone-forming cells.
Activated osteocalcin can bind calcium and contributes to the normal mineralisation of bone.
This creates an important relationship between vitamin K2 and bone metabolism.
Adequate vitamin K status is therefore important for maintaining normal bone structure and mineral metabolism.
Research has investigated K2 supplementation in relation to bone mineral density and fracture risk, although results vary depending on the population, form of K2 and study design.
Vitamin K2 and Arteries
Vitamin K2 is also involved in the activation of matrix Gla protein (MGP).
MGP is found in vascular tissue and is one of the body’s natural inhibitors of abnormal calcification.
When vitamin K-dependent proteins such as MGP are adequately activated, they can participate in mechanisms that help regulate calcium deposition in soft tissues.
This is the basis for the scientific interest in vitamin K2 and vascular calcification.
Dr. Berg particularly emphasises this relationship, describing K2 as helping keep calcium in bone rather than allowing it to accumulate in arteries.
However, it is important to distinguish the biological mechanism from clinical proof: although observational studies and mechanistic research are promising, there is still insufficient evidence to claim that K2 supplementation can reliably reverse arterial calcification in humans.
Vitamin K2 and Vitamin D3
Vitamin D and vitamin K2 have complementary roles in calcium metabolism.
Vitamin D increases intestinal absorption of calcium and supports calcium availability.
Vitamin K2 activates vitamin-K-dependent proteins involved in calcium utilisation and regulation.
This is why Berg and Ekberg commonly discuss vitamin D together with K2.
In simple terms:
Vitamin D3 → helps increase calcium availability
Vitamin K2 → helps regulate calcium utilisation
These nutrients therefore participate in interconnected aspects of calcium metabolism.
However, taking vitamin D without K2 should not automatically be described as causing arterial calcification. The relationship is more complex, and current evidence does not establish that vitamin D supplementation alone inevitably causes vascular calcification.
Vitamin K2 and Magnesium
Vitamin K2 also exists within a broader network of nutrients involved in bone and mineral metabolism.
Magnesium contributes to numerous enzymatic reactions and is important for normal bone and mineral metabolism.
Vitamin D, magnesium and vitamin K therefore participate in interconnected physiological processes rather than functioning as completely isolated nutrients.
A nutrient-dense diet remains the foundation for maintaining adequate mineral status.
MK-4 and MK-7
Vitamin K2 is not a single compound.
Two of the best-known forms are:
MK-4 (menaquinone-4)
and
MK-7 (menaquinone-7).
MK-4 is found in certain animal foods and can also be produced by the body from vitamin K1.
MK-7 is commonly associated with fermented foods, particularly natto, and has a longer half-life in the circulation than K1 and some other forms.
Both MK-4 and MK-7 are used in dietary supplements.
MK-7 and Absorption
Vitamin K is fat-soluble.
Dietary fat can therefore support the absorption of vitamin K from food and supplements.
MK-7 is particularly interesting because studies indicate that it is well absorbed and remains in circulation for longer than some other forms of vitamin K.
This longer half-life is one reason MK-7 is commonly used in nutritional supplements.
Vitamin K2 and Food Sources
Vitamin K2 is naturally present in a number of animal and fermented foods.
Important sources include:
- Natto
- Fermented cheeses
- Egg yolks
- Liver
- Meat
- Butter and other dairy products
Natto is particularly rich in MK-7.
William Li has also highlighted animal foods such as chicken thighs as a source of vitamin K2 and has discussed research into K2-containing foods and their potential biological effects.
The amount and form of K2 in foods can vary considerably depending on the food, animal diet and fermentation process.
Vitamin K2 and Fermented Foods
Fermentation is an important source of menaquinones.
Certain bacteria can produce vitamin K2 during fermentation, which is why traditionally fermented foods can contain meaningful amounts of different K2 forms.
Natto is one of the richest known dietary sources of MK-7.
Other fermented foods, particularly certain cheeses, can contain different menaquinones.
The exact amount depends on the bacterial strains and fermentation conditions.
Vitamin K2 and Cardiovascular Health
The relationship between vitamin K2 and cardiovascular health has attracted considerable scientific interest.
Observational studies have found associations between higher dietary menaquinone intake and lower levels of vascular calcification or cardiovascular outcomes in some populations.
However, observational associations do not prove that K2 supplementation prevents heart attacks or reverses atherosclerosis.
Clinical trials investigating whether vitamin K supplementation can meaningfully reduce vascular calcification are still limited.
Therefore, K2 should be viewed as an important nutrient involved in calcium regulation and vascular biology, rather than as a proven treatment for cardiovascular disease.
Vitamin K2 and Cancer Research
Vitamin K2 has also attracted interest in cancer research.
William Li has discussed vitamin K2 in the context of foods such as chicken and its potential effects on processes related to angiogenesis, the formation of new blood vessels that can support tumour growth.
Research into vitamin K compounds and cancer biology is ongoing.
Laboratory and mechanistic findings are interesting, but they should not be interpreted as evidence that vitamin K2 can prevent or treat cancer in humans.
Vitamin K2 Deficiency
Clinically significant vitamin K deficiency is relatively uncommon in healthy adults.
Deficiency is more likely to occur in situations involving fat-malabsorption disorders, certain medications or conditions that interfere with vitamin K metabolism.
Severe deficiency primarily affects blood clotting and can lead to abnormal bleeding.
Because vitamin K-dependent proteins are also involved in bone metabolism, inadequate vitamin K status may also affect normal bone mineralisation.
How Much Vitamin K Do We Need?
There is currently no separate official Recommended Dietary Allowance specifically for vitamin K2.
The adequate intake for total vitamin K in adults is approximately:
Men: 120 µg/day
Women: 90 µg/day
These values include vitamin K from food and supplements.
The current dietary reference values do not establish a separate daily requirement for MK-4, MK-7 or other individual K2 forms.
Vitamin K2 and Supplementation
Vitamin K2 is available in supplements, most commonly as MK-4 or MK-7.
MK-7 is frequently used because of its relatively long half-life and good absorption.
The appropriate amount depends on the individual’s diet, nutritional status, health circumstances and the purpose of supplementation.
More is not necessarily better.
Vitamin K supplementation is generally considered to have a low potential for toxicity, but it can have an important interaction with warfarin and certain other anticoagulant medications.
Anyone taking warfarin should maintain a consistent vitamin K intake and discuss supplementation with their healthcare professional.
Vitamin K2 and Other Nutrients
Vitamin K2 does not function completely in isolation.
Its role is connected with several other nutrients involved in bone and mineral metabolism.
Important relationships include:
Vitamin D3 + Vitamin K2 → complementary roles in calcium metabolism
Vitamin K2 + Magnesium → interconnected mineral and bone metabolism
Vitamin K2 + Calcium → regulation of calcium utilisation
Vitamin K2 + Vitamin D3 + adequate nutrition → broader support for bone health
These relationships demonstrate that calcium metabolism is a network of interacting nutrients and biological processes, rather than the function of one nutrient alone.
In Simple Terms
Vitamin K2 → helps activate vitamin-K-dependent proteins
Vitamin K2 → supports normal calcium regulation
Vitamin K2 → supports bone mineralisation
Vitamin K2 → activates osteocalcin
Vitamin K2 → activates matrix Gla protein (MGP)
Vitamin K2 → participates in mechanisms that help regulate vascular calcification
Vitamin K2 → works together with vitamin D in calcium metabolism
Vitamin K2 → exists mainly as MK-4 and MK-7
Vitamin K2 → is fat-soluble
Vitamin K2 → is found particularly in fermented foods and animal products
The Key Principle
Vitamin K2 is not simply a “bone vitamin.”
Its importance comes from its role in activating proteins that participate in calcium regulation, bone metabolism and vascular biology.
Vitamin D helps regulate calcium availability, while vitamin K-dependent proteins help the body use calcium within tissues where it is required.
This is why vitamin K2 has attracted so much interest in relation to bone strength, calcium metabolism and vascular health.
At the same time, the science needs to be interpreted carefully: K2 has strong biochemical plausibility and promising observational and mechanistic evidence, but it should not be presented as a proven treatment for arterial calcification, atherosclerosis or cancer.
The goal is adequate vitamin K status and balanced nutrition, not simply taking increasingly high doses of K2