Published: May 13, 2026 · Last updated: May 13, 2026
- Vitamin K2 (menaquinone) activates two proteins that direct calcium into bones and away from arteries. K1 from leafy greens does not perform this function well (NIH ODS, 2024)
- The Rotterdam Study followed 4,807 adults for 7 to 10 years and found those with the highest dietary K2 intake had a 57 percent lower risk of cardiovascular death and 27 percent lower coronary artery calcification (NIH ODS, 2024)
- Most Americans get very little K2 because it concentrates in foods we rarely eat: natto, hard cheeses, egg yolks from pasture-raised hens, and fermented dairy (Cleveland Clinic, 2024)
If you take a calcium supplement to protect your bones, you may also be unintentionally calcifying your arteries. Calcium does not know where to go. It deposits wherever the cells direct it, and after 50 those cellular directions get sloppy. The vitamin that tells calcium "this way, not that way" is K2, and almost nobody is getting enough.
K2 is not the same as K1. K1 is the leafy-green form that everyone learns about in nutrition class, and it mostly handles blood clotting in the liver. K2 is the form that activates two specific proteins, osteocalcin and matrix Gla protein, that escort calcium into bones and pull it out of arteries. The research base for K2 in cardiovascular and bone health has grown substantially since the Rotterdam Study results.
What K2 Actually Does
K2 activates osteocalcin, which binds calcium to the bone matrix and helps build bone density. It also activates matrix Gla protein in the vascular walls, which prevents calcium from depositing inside arteries where it stiffens vessels and accelerates atherosclerosis. According to (NIH ODS, 2024), both proteins are inactive without sufficient K2.
This is why the K2 story is unusual in the supplement world. Most vitamins do one thing well. K2 simultaneously addresses two of the biggest causes of mortality and disability in older adults: osteoporosis fractures and cardiovascular disease. The mechanism is the same: calcium routing.
The Rotterdam Study Numbers
The Rotterdam Study, a large prospective cohort of Dutch adults aged 55 and older, found that participants in the highest tertile of dietary K2 intake had a 57 percent lower cardiovascular mortality and a 27 percent lower coronary artery calcification score over 7 to 10 years of follow-up. The protective effect was specific to K2 (menaquinone), not K1 (phylloquinone).
(Mayo Clinic, 2024) characterizes the K2 evidence as promising but not yet definitive at the level of randomized controlled trials. Most data is observational. The Rotterdam findings have been replicated in several follow-on cohorts, but a large RCT specifically testing K2 supplementation for cardiovascular endpoints has not yet been completed.
Why You Probably Are Not Getting Enough
K2 is found in foods that have largely disappeared from the modern Western diet. (Cleveland Clinic, 2024) lists the richest sources: natto (fermented soybeans, common in Japan, rare elsewhere), aged hard cheeses like Gouda and Edam, egg yolks from pasture-raised hens, butter from grass-fed cows, and fermented dairy. Industrial agriculture's shift to grain-fed livestock dramatically reduced K2 in eggs, dairy, and butter starting in the mid-20th century.
The result is a population-wide K2 deficit that did not exist 100 years ago. People eating plenty of K1-rich leafy greens are not protected, because the body converts only a small percentage of K1 to K2.
K2 in Two Forms: MK-4 and MK-7
K2 comes in two main supplement forms. MK-4 has a short half-life (about 1 hour) and is used in Japan at high pharmacological doses (45 mg) to treat osteoporosis. MK-7 is the long-half-life form (about 3 days) found in fermented foods, and it is the form most commonly used in everyday supplements at doses of 90 to 180 micrograms. MK-7 is the more practical choice for cardiovascular and bone support because its long half-life means daily dosing produces stable blood levels.
K2 is fat-soluble. Take it with a meal that contains some fat. Olive oil, eggs, avocado, or nuts in the same meal all work.
Who Should Be Careful
K2 supplementation interacts with warfarin (Coumadin) because warfarin works by blocking vitamin K-dependent clotting proteins. If you take warfarin, do not start K2 without talking to your doctor. Newer anticoagulants (apixaban, rivaroxaban) do not have this interaction. Most other medications are fine with K2.
For more on supplements that move the needle after 50, see our piece on which magnesium form actually works.
To your health,
Ageless Coach
Age Strong. Live Long.
Trusted Sources Behind This Article
This content is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Reading this article does not create a provider-patient relationship. Always consult your physician or qualified healthcare provider before making changes to your diet, exercise, or health routine. Ageless Coach is not liable for any actions taken based on this information.
Frequently Asked Questions
Want one verified-science article like this every week?
Get Better Health, Weekly