Quick answer: Vitamin K2 is worth considering if you take vitamin D, have a family history of osteoporosis or stiff arteries, or have been told you have “calcium issues.” K2 activates proteins that help put calcium into bones and teeth and keep it out of soft tissues such as arteries. MK-7 is the longer-acting form used most often. Anyone taking warfarin must talk to their prescriber before using any vitamin K.
Key takeaways
Vitamin K2 activates proteins that help direct calcium into bone and away from arteries.
It may be worth considering for people who take vitamin D daily or have a family history of osteoporosis or stiff arteries.
K2 is a long-game nutrient, and anyone taking warfarin or another vitamin K antagonist should speak with their prescriber first.
Who should consider vitamin K2?
Vitamin K2 may be worth considering for people who take vitamin D every day and for anyone with a family history of osteoporosis or arterial stiffness. It may also fit people who have been told they have calcium deposits or “calcium issues,” those with frequent tartar buildup or weak dental health, and people whose diet includes few fermented foods, aged cheeses or egg yolks.
What vitamin K2 does
Vitamin K2 activates proteins such as osteocalcin (which helps bind calcium into bone) and matrix Gla protein (which helps keep calcium out of blood vessel walls). I think of vitamin D without K2 as sending calcium into the bloodstream without a traffic director. D, K2 and magnesium are a trio I discuss often in my practice.
Why K2 is a long-game nutrient
K2 is quiet. You will not “feel” it in three days. That is exactly why it belongs in a longevity-minded plan rather than a symptom-chasing one. With age, tissues tend to stiffen and minerals can end up in the wrong places. Supporting bones that stay dense and vessels that stay flexible is part of aging well. Related: osteoporosis prevention and bone health essentials.
K1 vs. K2, and MK-4 vs. MK-7
- Vitamin K1: found in leafy greens; mainly supports blood clotting.
- Vitamin K2: found in natto, some aged cheeses, egg yolks and fermented foods; more involved in calcium handling.
- MK-7: a longer-lasting form of K2 that stays in the blood longer than MK-4.
If you work with me, the D and K2 products I use are in my Fullscript dispensary. See also who should consider vitamin D3 and who should consider magnesium.
Safety
According to the NIH Office of Dietary Supplements, the adequate intake for total vitamin K is 90 mcg a day for adult women and 120 mcg a day for adult men, and no upper limit has been set. The big exception is warfarin (Coumadin): vitamin K directly affects how it works, so changes in vitamin K intake must be coordinated with your prescriber.
When to see a naturopathic doctor
It may be time to see a naturopathic doctor if you take vitamin D and nobody has talked to you about K2, or if you have osteopenia, osteoporosis or a family history of either. The same is true if you have been told you have arterial or other calcium deposits, or if you take a blood thinner and want to understand your options safely.
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Questions to bring to your clinician
These questions can help you get the most out of your next visit.
Since I take vitamin D, would adding K2 make sense for my bones and heart?
Could vitamin K2 interact with any of my current medications or other supplements?
Would any labs or health history details help us decide whether vitamin K2 makes sense for me?
How would we tell whether vitamin K2 is a good fit for me, and when should we check in again?
Practitioner-grade options in my Fullscript catalog: if you and your clinician decide a supplement makes sense, my supplement guide by health goal links to the practitioner-grade products I trust.
Frequently asked questions
Should I take vitamin K2 with vitamin D?
Many people pair them because vitamin D increases calcium absorption and K2 helps direct calcium to bone. Ask your provider whether the combination fits you.
Can I take vitamin K2 if I am on a blood thinner?
Not without talking to your prescriber first. Vitamin K affects warfarin directly. Other anticoagulants work differently, but your prescriber should still know.
What foods contain vitamin K2?
Natto (fermented soybeans) is by far the richest source. Some aged cheeses, egg yolks and other fermented foods provide smaller amounts.
How long does K2 take to work?
K2 supports long-term bone and vascular health, so it is not something you feel quickly. Bone density changes are tracked over months to years.
Sources
- Knapen MH, et al. Three-year low-dose menaquinone-7 supplementation helps decrease bone loss in healthy postmenopausal women. Osteoporos Int 2013. PMID: 23525894. https://pubmed.ncbi.nlm.nih.gov/23525894/
- Luo G, et al. Spontaneous calcification of arteries and cartilage in mice lacking matrix GLA protein. Nature 1997. PMID: 9052783. https://pubmed.ncbi.nlm.nih.gov/9052783/
- Schurgers LJ, Vermeer C. Determination of phylloquinone and menaquinones in food. Effect of food matrix on circulating vitamin K concentrations. Haemostasis 2000. PMID: 11356998. https://pubmed.ncbi.nlm.nih.gov/11356998/
- Sato T, Schurgers LJ, Uenishi K. Comparison of menaquinone-4 and menaquinone-7 bioavailability in healthy women. Nutr J 2012. PMID: 23140417. https://pmc.ncbi.nlm.nih.gov/articles/PMC3502319/
- Schurgers LJ, et al. Vitamin K-containing dietary supplements: comparison of synthetic vitamin K1 and natto-derived menaquinone-7. Blood 2007. PMID: 17158229. https://pubmed.ncbi.nlm.nih.gov/17158229/
- NIH Office of Dietary Supplements: Vitamin K (Consumer Fact Sheet)
- NIH Office of Dietary Supplements: Vitamin K (Health Professional Fact Sheet)
This article is for educational purposes only and is not medical advice. It does not replace an individual evaluation. Talk with your healthcare provider before starting supplements or changing medications, especially if you are pregnant, nursing, or managing a health condition.
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