Vitamin K2 is found in animal-based foods, like beef liver and cheese. It’s essential to many aspects of your health, including blood clotting, calcium metabolism, and heart health. Some think vitamin K2 may be the missing link between diet and several chronic diseases.

Vitamin K was discovered in 1929 as an essential nutrient for blood coagulation, the scientific term for blood clotting.

The initial discovery was reported in a German scientific journal, where it was called “Koagulationsvitamin.” That’s where the K in vitamin K comes from.

There are two main forms of vitamin K:

  • Vitamin K1 (phylloquinone): found in plant foods like leafy greens
  • Vitamin K2 (menaquinone): found in animal foods and fermented foods, also produced by gut bacteria

Vitamin K2 can be further divided into several different subtypes. The most important ones are MK-4 and MK-7.

Calcium buildup in the arteries around your heart is a major risk factor for heart disease.

Anything that can reduce this calcium buildup may help prevent heart disease. Vitamin K is believed to help by preventing calcium from being deposited in your arteries.

In a 2019 meta-analysis of 21 studies and 222,592 participants, an increased dietary intake of either vitamin K1 or K2 was linked with a moderately reduced risk of coronary heart disease, although not with mortality.

A 2020 review of the association between dietary vitamin K and risks of coronary heart disease in adults found a lower risk of coronary heart disease with vitamin K supplementation.

The review noted that K2 showed the most promise, mentioning that much of the ingested K1 is transformed into K2 in the body.

However, remember that the studies were observational studies, which cannot prove cause and effect. Long-term controlled trials on vitamin K2 and heart disease are needed.

Still, there is a highly believable biological mechanism for its effectiveness and strong positive correlations with heart health in observational studies.

Osteoporosis — which translates to “porous bones” — is common, especially among older adults. It strongly increases the risk of fractures.

As mentioned above, vitamin K2 plays a central role in calcium metabolism, the main mineral found in your bones and teeth.

Vitamin K2 activates the calcium-binding actions of two proteins — matrix GLA protein and osteocalcin, which help to build and maintain bones.

Interestingly, there is also substantial evidence from controlled studies that K2 may provide major benefits for bone health.

A 2022 meta-analysis of 16 studies in 6,425 postmenopausal women found that those taking vitamin K2 supplements had a positive effect on bone mineralization and increased bone strength.

However, a 2023 review of trials conducted in the past decade shows conflicting results.

More high quality, longer-term trials are needed to prove benefits for preventing and treating osteoporosis, improving bone mineral density, and preventing fractures.

A 2023 review of 4,965 elderly individuals concluded that regular vitamin K supplementation coupled with moderate fiber intake was effective at helping to prevent tooth loss from periodontal disease, particularly in males.

This effectiveness was not as evident for Black test subjects as other populations, so more studies are needed.

Based on animal studies and the role vitamin K2 plays in bone metabolism, it’s reasonable to assume that this nutrient affects dental health as well.

One of the main proteins regulating dental health is osteocalcin — the same protein that is critical to bone metabolism and is activated by vitamin K2.

Osteocalcin triggers a mechanism that stimulates the growth of new bone and new dentin, which is the calcified tissue underneath the enamel of your teeth.

Vitamins A and D are also believed to play an important role here, working synergistically with vitamin K2.

Several studies have been done on vitamin K2 and certain types of cancer.

Cell and animal studies suggest that K2 mayinhibit the growth of liver cancer cells. Still, larger, well-controlled, long-term studies are needed to show the benefit of reduced liver cancer recurrence rates and improved survival.

Some studies have linked a high intake of MK with an increased risk of breast cancer. More high quality studies are needed before any strong claims can be made.

Several widely available foods are rich sources of vitamin K1, but vitamin K2 is less common.

Your body can partly convert vitamin K1 to K2. This is useful because the amount of vitamin K1 in a typical diet is nine times that of vitamin K2.

However, only 10-15% of ingested vitamin K1 is absorbed in the digestive tract, so absorbed K1 makes up about 50% of all vitamin K in the diet.

Current evidence indicates that the conversion process is inefficient. As a result, you may benefit much more from eating vitamin K2 directly.

Gut bacteria in your large intestine also produce vitamin K2. Some evidence suggests that broad-spectrum antibiotics contribute to K2 deficiency.

Still, the average intake of this important nutrient is incredibly low in the modern diet.

Vitamin K2 is mainly found in certain animal and fermented foods. Rich animal sources include high fat dairy products from cows and egg yolks, as well as liver and other organ meats.

Vitamin K is fat-soluble vitamin, which means low fat and lean animal products don’t contain much of it.

Animal foods contain the MK-4 subtype, while fermented foods like sauerkraut, natto, and miso pack more of the longer subtypes, MK-5 to MK-14.

Taking supplements can be a helpful alternative if these foods are inaccessible. Talk with a healthcare professional before adding extra vitamin K2 to your diet.

The benefits of supplementing with K2 may be enhanced even further when combined with a vitamin D supplement. These two vitamins have synergistic effects, which means they may work together.

How do vitamins K1 and K2 work?

One of the most important functions of vitamin K is to regulate calcium deposition. In other words, it promotes the calcification of bones and prevents the calcification of blood vessels and kidneys.

Some scientists have suggested that the roles of vitamins K1 and K2 are quite different, and many feel that they should be classified as separate nutrients altogether.

However, more human studies are needed before the functional differences between vitamins K1 and K2 can be fully understood.

Is vitamin K safe?

Vitamin K has a very low potential for toxicity. This is why there is no established Tolerable Upper Intake Level (UL) set for vitamin K. There is no known toxicity for vitamin K1 or K2 from food or supplements.

Does vitamin K interact with any medications?

People taking blood thinning medications like warfarin are counseled to keep their vitamin K intake consistent and avoid large quantities of vitamin K-rich foods or large fluctuations in vitamin K intake.

This is because sudden increases in vitamin K may interact with the medication, leading to increased or decreased blood clotting.

Vitamin K is a group of nutrients divided into vitamins K1 and K2.

Vitamin K1 is involved in blood coagulation, and vitamin K2 benefits bone and heart health. However, more studies on the roles of vitamin K subtypes are needed.

Some scientists are convinced that people at risk of heart disease should regularly use vitamin K2 supplements. Others point out that more studies are needed before any solid recommendations can be made.

However, it’s clear that vitamin K plays an essential role in body function. To maintain good health, get adequate amounts of vitamins K1 and K2 through your diet.