Phylloquinone and menaquinones: how the two vitamin K forms differ
What it found
Vitamin K1 (phylloquinone) and vitamin K2 (menaquinones) differ in where they come from, how well they are absorbed and what they do in the body.
Much of the evidence for K2's wider roles comes from lab and animal work, with some studies in people.
What they found
Studies in people
Absorption and staying power
After eating, blood levels of K2 in the form MK-7 were 10-fold higher than K1. Long-chain menaquinones such as MK-7 and MK-9 stay in the circulation longer than K1, so they are available longer to reach tissues outside the liver.
Heart and blood vessels
In trials with healthy people and patients, MK-7 has been shown to have a long-term protective effect on the development of blood vessel calcification. In one study looking at all vitamin K1 and K2 forms, only K2 was helpful for heart health, not K1.
Studies in people and animals
Bones and fractures
Studies in groups over the age of 50 show that vitamin K2 improves bone quality, which in turn lowers fracture risk. In lab tests, vitamin K2 treatment supported the development of bone-forming cells from bone marrow stem cells.
Diabetes risk
In the largest study, with 38,000 men and women aged 20 to 70, just 10 micrograms a day of K2 was linked to a 7% lower risk of developing diabetes. In lab tests, K2 activates osteocalcin, which has been shown to help pancreatic beta cells grow and make more insulin.
Cancer and other conditions
Lab studies found K2 alone prevented growth and spread of several cancer cell lines, and some case reports describe cancer improving alongside standard treatment. K2 has also been studied in liver disease, chronic kidney disease, the immune system, neurological disease and obesity, but the authors say more research is needed.
Other findings
Food sources
Vitamin K1 is the main form in the diet and is found mostly in green vegetables and plant chlorophylls, such as spinach, cabbage and kale. Vitamin K2 is made by bacteria and is mainly found in fermented foods, meat and dairy, with natto the richest source.
What the authors conclude
“When exploring the non-coagulation, extrahepatic activity of vitamin K, it is clear that K2 in its various forms is the highlight of such activity.”
Also in their conclusions
- They say that K2 is proving beneficial for heart and blood vessel disease and for bone metabolism.
- They note that while K2 has improved outcomes in many clinical trials, the exact mechanism of action remains to be unravelled.
- They argue that differences between K1 and K2 merit recognition among national and international regulatory organisations and remain open to research.
How it was done
Vitamin K was first known only for blood clotting, but non-clotting functions have since been discovered. The authors wanted to set out the differences between K1 and K2 by source and function, with a focus on these non-clotting roles.
The authors pulled together published research on vitamin K1 and K2, covering their food sources, how they are absorbed and distributed, and their roles in health and disease. They also reviewed intake recommendations and measurement methods.
What it can’t tell you
- This is a review of other studies, not a new experiment, so it cannot prove cause and effect.
- Many of the findings come from lab tests or animal studies, which cannot show what happens in people.
- Some of the human findings come from population studies, which can show a link but not that vitamin K2 caused the outcome.
Who paid
- Funding
- Funded by H2020 Marie Skłodowska-Curie Actions; Deutsche Forschungsgemeinschaft (from the PubMed record).
- Conflicts
- Frode Bohan and Eric Anderson are employed by NattoPharma ASA, which is industrial partner of the Marie Skłodowska-Curie grants No 722609 and No 675111.
- Authors work at
- RWTH Aachen University, Germany; Cardiovascular Research Institute Maastricht, The Netherlands; International Science & Health Foundation, Poland
The paper
- Title
- Vitamin K: Double Bonds beyond Coagulation Insights into Differences between Vitamin K1 and K2 in Health and Disease
- Type
- ReviewThe authors read earlier studies and describe what they found. It isn’t a new study.
- Evidence
- Studies in people · animals · lab
- Summarised from
- Full text
- Licence
- CC BY. Words in quotation marks are the authors’; the rest is our summary.
- Cite
- Halder M, Petsophonsakul P, Akbulut AC, et al (2019). Vitamin K: Double Bonds beyond Coagulation Insights into Differences between Vitamin K1 and K2 in Health and Disease. International journal of molecular sciences. doi:10.3390/ijms20040896Free full textPubMed 30791399DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error