Vitamin K2: Everything You Need to Know

Many people have never heard of vitamin K2. This vitamin is found in fewer foods than K1. It’s found in animal-based foods, like beef liver and cheese, while K1 is found in plant foods.

However, this powerful nutrient plays an essential role in many aspects of your health. In fact, some think that vitamin K2 may be the missing link between diet and several chronic diseases.

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Vitamin K was discovered in 1929 as an essential nutrient for blood coagulation, which is 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 (1).

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 (2, 3)

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

Summary

Vitamin K was initially discovered as a nutrient involved in blood clotting. There are two forms: K1 (found in plant foods) and K2 (found in animal and fermented foods).

Vitamin K activates proteins that play a role in blood clotting, calcium metabolism, and heart health.

One of its most important functions is to regulate calcium deposition. In other words, it promotes the calcification of bones and prevents the calcification of blood vessels and kidneys (4).

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.

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.

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 (5).

Summary

Vitamin K plays an essential role in blood clotting, heart health, and bone health.

Calcium buildup in the arteries around your heart is a huge risk factor for heart disease (6, 7).

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 (4).

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 (8).

A 2020 review about 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, while also mentioning that much of the ingested K1 is transformed to K2 in the body (9).

However, keep in mind 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.

Summary

A higher intake of vitamin K2 is strongly associated with a reduced risk of heart disease. Vitamin K1 appears to be less useful or ineffective.

Osteoporosis — which translates to the phrase “porous bones” — is a common problem in Western countries.

It is seen especially among older women and strongly raises the risk of fractures.

As mentioned above, vitamin K2 plays a central role in the metabolism of calcium, 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 (10).

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

A meta-analysis of 16 studies in 6425 postmenopausal women found that those taking vitamin K2 supplements had a positive effect on bone mineralization and increased bone strength. (11).

An older 2006 review of studies in Japanese women observed similar benefits, though very high doses were used in these cases. Out of 13 studies, only one failed to show significant improvement.

Seven of these trials, which took fractures into consideration, found that vitamin K2 reduced spinal fractures by 60%, hip fractures by 77%, and all non-spinal fractures by 81% (12).

In line with these findings, vitamin K supplements are officially recommended for preventing and treating osteoporosis in Japan (13).

Summary

Vitamin K2 plays an essential role in bone metabolism, and studies suggest that it can help prevent osteoporosis and fractures.

Researchers have speculated that vitamin K2 may affect dental health.

A 2023 review of 4965 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 (14).

This effectiveness was not as evident for Black test subjects compared to other populations, so clearly 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 regulating proteins in dental health is osteocalcin — the same protein that is critical to bone metabolism and is activated by vitamin K2 (15).

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 (16).

Vitamins A and D are also believed to play an important role here, working synergistically with vitamin K2 (17).

Summary

It’s believed that vitamin K2 may play a critical role in dental health, but human studies showing the benefits of supplements in this area are currently lacking.

Cancer is a common cause of death in Western countries.

Even though modern medicine has found many ways to treat it, new cancer cases are still rising. Finding effective prevention strategies is of utmost importance.

Interestingly, several studies have been done on vitamin K2 and certain types of cancer.

Two older clinical studies suggest that vitamin K2 reduces the recurrence of liver cancer and increases survival times (18, 19).

However, some studies have linked high intake of MK with an increased risk of breast cancer (20).

More high quality studies are needed before any strong claims can be made.

Summary

Vitamin K2 has been found to improve survival in patients with liver cancer. But more studies are needed.

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 actual absorbed K1 makes up about 50% of all vitamin K in the diet (21).

However, 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 (22).

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, which most people don’t eat much of.

Rich animal sources include high fat dairy products from grass-fed cows and egg yolks, as well as liver and other organ meats (23).

Vitamin K is fat-soluble, 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 (24).

If these foods are inaccessible to you, taking supplements is a valid alternative. Talk to a healthcare provider before adding extra vitamin K2 to your diet.

A selection of K2 supplements can be found on Amazon.

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 (25).

Though this needs to be studied in more detail, current research on vitamin K2 and health is promising. In fact, it potentially may have lifesaving implications for many people.

Summary

You can get vitamin K2 from high fat dairy products, egg yolk, liver, and fermented foods, such as sauerkraut.

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, make sure to get adequate amounts of vitamins K1 and K2 through your diet.