Most people have never heard of vitamin K2.
This vitamin is rare in the Western diet and hasn't received much mainstream attention.
However, this powerful nutrient plays an essential role in many aspects of your health.
In fact, 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 (blood clotting).
The initial discovery was reported in a German scientific journal, where it was called “Koagulationsvitamin” — which is where the "K" comes from (1).
It was also discovered by the dentist Weston Price, who travelled the world in the early 20th century studying the relationship between diet and disease in different populations.
He found that the non-industrial diets were high in some unidentified nutrient, which seemed to provide protection against tooth decay and chronic disease.
He referred to this mystery nutrient as “activator X,” which is now believed to have been vitamin K2 (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 ().
Vitamin K2 can be further divided into several different subtypes, the most important ones being 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 (, ).
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.
This idea is supported by an animal study showing that vitamin K2 (MK-4) reduced blood vessel calcification whereas vitamin K1 did not ().
Controlled studies in people also observe that vitamin K2 supplements generally improve bone and heart health, while vitamin K1 has no significant benefits ().
However, more human studies are needed before the functional differences between vitamins K1 and K2 can be fully understood.
Summary Vitamin K plays an essential role in blood clotting, heart health and bone health.
Calcium build-up in the arteries around your heart is a huge risk factor for heart disease (, , ).
Therefore, anything that can reduce this calcium accumulation may help prevent heart disease.
Vitamin K is believed to help by preventing calcium from being deposited in your arteries ().
In one study spanning 7–10 years, people with the highest intake of vitamin K2 were 52% less likely to develop artery calcification and had a 57% lower risk of dying from heart disease ().
Another study in 16,057 women found that participants with the highest intake of vitamin K2 had a much lower risk of heart disease — for every 10 mcg of K2 they consumed per day, heart disease risk was reduced by 9% ().
On the other hand, vitamin K1 had no influence in either of those studies.
However, keep in mind that the above studies are observational studies, which cannot prove cause and effect.
The few controlled studies that have been conducted used vitamin K1, which seems to be ineffective ().
Long-term controlled trials on vitamin K2 and heart disease are needed.
Still, there is a highly plausible 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 “porous bones” — is a common problem in Western countries.
It prevails 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 (, ).
Interestingly, there is also substantial evidence from controlled studies that K2 may provide major benefits for bone health.
A 3-year study in 244 postmenopausal women found that those taking vitamin K2 supplements had much slower decreases in age-related bone mineral density (16).
Long-term studies in Japanese women have 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% ().
In line with these findings, vitamin K supplements are officially recommended for preventing and treating osteoporosis in Japan ().
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.
However, no human studies have tested this directly.
Based on animal studies and the role vitamin K2 plays in bone metabolism, it’s reasonable to assume that this nutrient impacts 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 ().
Osteocalcin triggers a mechanism that stimulates the growth of 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 ().
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 on the rise.
Therefore, finding effective prevention strategies is of utmost importance.
Interestingly, several studies have been done on vitamin K2 and certain types of cancer.
Two clinical studies suggest that vitamin K2 reduces recurrence of liver cancer and increases survival times (, ).
Additionally, an observational study in 11,000 men found that a high vitamin K2 intake was linked to a 63% lower risk of advanced prostate cancer, whereas vitamin K1 had no effect ().
However, 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. Men who consume the highest amounts of K2 appear to have a lower risk of advanced prostate cancer.
Several widely available foods are rich sources of vitamin K1, but vitamin K2 less common.
Your body can partly convert vitamin K1 to K2. This is useful, as the amount of vitamin K1 in a typical diet is ten times that of vitamin K2.
However, current evidence indicates that the conversion process is inefficient. As a result, you may benefit much more from eating vitamin K2 directly.
Vitamin K2 is also produced by gut bacteria in your large intestine. 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, which most people don't eat much of.
Rich animal sources include high-fat dairy products from grass-fed cows, egg yolks, as well as liver and other organ meats ().
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 ().
If these foods are inaccessible to you, taking supplements is a valid alternative. An excellent 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, as these two vitamins have synergistic effects ().
Though this needs to be studied in more detail, current research on vitamin K2 and health is promising.
In fact, it may have life-saving 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 that are 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 vitamin K2 supplements should be regularly used by people at risk of heart disease. 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.