Vitamin K2: Everything You Need to Know
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 health.
In fact, vitamin K2 may just be the "missing link" between diet and several killer 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. That's where the "K" comes from (1).
It was also discovered by the legendary 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, but this is now believed to have been Vitamin K2.
There are two main forms of Vitamin K... K1 (phylloquinone) is found in plant foods like leafy greens, whereas Vitamin K2 (menaquinone) is found in animal foods and fermented foods (2).
Vitamin K2 can be further divided into several different subtypes, but the most important ones are MK-4 and MK-7.
Bottom Line: Vitamin K was initially discovered as a nutrient involved in blood clotting. There are two forms, K1 (plants) and K2 (animal foods).
Calcium is an incredibly important mineral.
It is more than just building material for bones and teeth, it plays a crucial role in all kinds of biological processes (3).
The main function of Vitamin K is modifying proteins to give them the ability to bind calcium.
In this way, it "activates" the calcium-binding properties of proteins.
However... the roles of Vitamin K1 and K2 are quite different and many feel that they should be classified as separate nutrients altogether.
Vitamin K1 is mostly used by the liver to activate calcium-binding proteins involved in blood clotting, while K2 is used to activate proteins that regulate where calcium ends up in the body (4).
Bottom Line: The main function of Vitamin K is to activate the calcium-binding properties of proteins. K1 is mostly involved in blood clotting, while K2 helps regulate where calcium ends up in the body.
For this reason, anything that can reduce this accumulation of calcium may help prevent heart disease.
This is where vitamin K2 is believed to help, by helping to prevent calcium from being deposited in the arteries (8).
In the Rotterdam study, those who had the highest intake of Vitamin K2 were 52% less likely to develop calcification of the arteries, and had a 57% lower risk of dying from heart disease, over a 7-10 year period (9).
Another study of 16,057 women found that participants with the highest intake of vitamin K2 had a much lower risk of heart disease. For every 10 micrograms of K2 they consumed per day, the risk of heart disease was reduced by 9% (10).
For the record, vitamin K1 had no influence in either of those studies.
However... keep in mind that the studies above are so-called observational studies, which can not prove cause and effect.
Unfortunately, the few controlled trials that have been done used the K1 form, which seems to be ineffective (11).
We are in desperate need of some long-term controlled trials on K2 and heart disease. There is a highly plausible biological mechanism for its effectiveness, and strong correlations found in observational studies.
The importance of this can not be overstated... cardiovascular disease is the world's most common cause of death. It killed 14 million people in the year 2012 alone (12).
Bottom Line: A higher intake of vitamin K2 is strongly associated with a reduced risk of heart disease. Vitamin K1 appears to be less useful.
Osteoporosis ("porous" bones) is a common problem in Western countries.
It is especially common among elderly women and strongly raises the risk of fractures.
As mentioned above, Vitamin K2 plays a central role in calcium metabolism, the main mineral found in bones.
Interestingly, there is also quite a bit of evidence from controlled trials that K2 has major benefits for bone health.
A 3-year trial in 244 postmenopausal women found that those taking vitamin K2 supplements had much slower decreases in age-related bone mineral density (15).
Lengthy studies on Japanese women have shown similar benefits, although they did use very high doses. Out of 13 trials, only one failed to show significant improvement.
Seven of those trials also reported fractures and found that vitamin K2 reduced spinal fractures by 60%, hip fractures by 77% and all non-spinal fractures by 81% (16).
In line with these findings, the Japanese officially recommend vitamin K supplementation for the prevention and treatment of osteoporosis (17).
Bottom Line: 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 has in bone metabolism, it is reasonable to assume that it impacts dental health too.
Vitamin A and D are also believed to play an important role here, working synergistically with vitamin K2 (23).
Bottom Line: It is believed that Vitamin K2 may play a critical role in dental health, but there are currently no human studies to support this.
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.
An observational study on 11,000 men also found that a high vitamin K2 intake was linked to a 63% lower risk of advanced prostate cancer. Vitamin K1 had no effect (26).
Hopefully we will have some better studies on this in the near future.
Bottom Line: Vitamin K2 has been found to improve survival in patients with liver cancer. Men who consume the most K2 have a lower risk of advanced prostate cancer.
Humans can partly convert vitamin K1 to K2 in the body. This is useful because 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, because we benefit much more from eating vitamin K2 directly.
Unfortunately, the average intake of this important nutrient is incredibly low in the modern diet.
Vitamin K2 is mainly found in certain animal foods and fermented foods, which most people don't eat much of.
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 contain more of the longer subtypes, MK-5 to MK-14 (30).
If those foods are inaccessible to you, then supplementation is a valid alternative.
Although this needs to be studied a lot further, the current research on Vitamin K2 and health is extremely promising.
It could have life-saving implications for a lot of people.