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Vitamin K2 (Menaquinones)
Vitamin K2 is the switch that tells calcium where to go: into bone, out of your artery walls. It is not the K1 in spinach. The people who eat the most K2 die of heart disease at half the rate of the people who eat the least, and their bones thin more slowly Geleijnse et al. 2004. Closing that gap costs the price of a coffee a month. The catch: you never feel it working, and the payoff shows up on scans decades out.
Do ยท Daily Evidence Emerging Chapter Supplements

Calcium has two jobs: build bone and stay out of arteries. Two proteins steer it. Osteocalcin anchors it into bone, matrix Gla protein keeps it off artery walls, and both are inert until switched on. K2 is the switch 1. Without enough, calcium that should harden your skeleton drifts into the lining of your aorta. Twenty years of that and your bones are thinner and your arteries stiffer than they should be.

The population signal is strong; the definitive trial is missing. Three large European cohorts followed people for years: those eating more K2 had less arterial calcification and lower heart-disease death, while K1 intake in the same people did nothing 2 3. That split is what makes it credible; a generic "eats healthy" effect would have caught both forms.

In 244 postmenopausal women, three years of MK-7 slowed carotid-artery stiffening and roughly halved inactive matrix Gla protein 4, and slowed bone loss at spine and hip 5. But the hard-outcome data is thin enough that a Cochrane review declined to recommend K2 for heart-disease prevention 6. The mechanism holds and the markers move; the large endpoint trial hasn't been run.

Buy MK-7, take it with a fatty meal, ignore how it feels. The long-acting form is the one the European trials used; short-lived MK-4 is inert at supplement doses.

You feel nothing, on any timescale. That is the intervention, not a flaw in it.

  • Two weeks: the K2 level in your blood reaches steady state 7. Undetectable to you.
  • Three years: at the trial dose, carotid stiffness runs measurably lower and bone density has declined less than it would have 5 4. Your cardiologist sees it on imaging; you don't.
  • Decades: the arithmetic from the cohorts becomes events that don't happen โ€” the heart attack, the hip fracture from an icy step.

This is the silent end of the spectrum, the same bucket as keeping blood pressure in range. The way you know it worked is the trouble that never arrives.

The fine print โ€” when to skip it, and what people get wrong

"Spinach gives you all the K you need" is wrong: K1 barely reaches bone or artery, and K1 supplements did nothing for bone density over three years 8. K2 also doesn't "work in a week"; the scan changes took three years 4.

Three ways to get nothing: buying "vitamin K" that's actually K1 or a token MK-4 dose; taking it on an empty stomach; quitting after a month because nothing happened. The last is the common one; treat it as maintenance and leave it running.

References
  1. 1Iwamoto J (2014). Vitamin K2 therapy for postmenopausal osteoporosis. Nutrients. link
  2. 2Gast GCM, de Roos NM, Sluijs I et al. (2009). A high menaquinone intake reduces the incidence of coronary heart disease. Nutrition, Metabolism and Cardiovascular Diseases. link
  3. 3Beulens JWJ, Bots ML, Atsma F et al. (2009). High dietary menaquinone intake is associated with reduced coronary calcification. Atherosclerosis. link
  4. 4Knapen MHJ, Braam LAJLM, Drummen NE et al. (2015). Menaquinone-7 supplementation improves arterial stiffness in healthy postmenopausal women: a double-blind randomised clinical trial. Thrombosis and Haemostasis. link
  5. 5Knapen MHJ, Drummen NE, Smit E et al. (2013). Three-year low-dose menaquinone-7 supplementation helps decrease bone loss in healthy postmenopausal women. Osteoporosis International. link
  6. 6Hartley L, Clar C, Ghannam O et al. (2015). Vitamin K for the primary prevention of cardiovascular disease. Cochrane Database of Systematic Reviews. link
  7. 7Theuwissen E, Magdeleyns EJ, Braam LAJLM et al. (2014). Vitamin K status in healthy volunteers. Food and Function. link
  8. 8Booth SL, Dallal G, Shea MK et al. (2008). Effect of vitamin K supplementation on bone loss in elderly men and women. Journal of Clinical Endocrinology and Metabolism. link
Related in the handbook (6)
Works well with
  • โ€” K2 is part of the slow bone-protection story; it helps keep calcium going into bone over years.
Related
  • โ€” Keeping bone density up isn't just calcium and vitamin D; K2 helps put that calcium into bone rather than into your arteries.
  • โ€” The arterial calcium this scan finds is what K2 is meant to help prevent depositing in the first place.
  • โ€” Vitamin K2 is a textbook example of why warfarin patients must vet supplements with a clinician.
  • โ€” If you're taking K2 and D for your bones, magnesium is the third leg most people are quietly short on.
  • โ€” Vitamin D raises calcium absorption; K2 is what steers that calcium where it belongs.
ยท
566