Molecule
Vitamin K2 (Menaquinone)
Vitamin K2, primarily as menaquinone-7 (MK-7)
A fat-soluble vitamin that activates proteins controlling where calcium goes in the body. Trial evidence shows it can reduce fracture odds without a matching, statistically significant bump in bone density.
Summary Can vitamin K2 strengthen bones and prevent calcium buildup in arteries? Show / hide ↓
Vitamin K2 is a fat-soluble vitamin that helps switch on proteins directing calcium into bones and away from soft tissues such as artery walls. In a 3-year randomized trial, postmenopausal women with low bone density who took MK-7, a form of K2, had improvements in bone density and bone structure. A 2022 review combining 20 studies and 3,950 people found lower odds of clinical fractures and spinal fractures, but it included both K1 and K2. The average change in bone density at the top of the thigh was not clear and could have been due to chance. Studies of artery calcification have mainly involved people on dialysis, not healthy adults, and have not shown fewer heart attacks or strokes.
What this means for you: K2 may help reduce fractures, but the evidence is not consistent enough to confirm how it works or that it protects healthy arteries. Do not treat it as an established bone or heart supplement.
conflicting evidenceVitamin K2 activates, through carboxylation, a small set of proteins that determine where calcium is deposited in the body. Two matter most here: osteocalcin, which helps bind calcium into bone, and matrix Gla protein, which inhibits calcium deposits in soft tissue like arterial walls. That dual role, bone in, arteries out, is the basis for most K2 supplementation claims.
A 3-year randomized, placebo-controlled trial in postmenopausal women with osteopenia gave MK-7 and measured bone mineral density and microarchitecture, reporting improvements in the treatment group compared to placebo [1]. A separate 2022 systematic review and meta-analysis pooled 20 studies (3,950 subjects, 6 to 36 months follow-up, doses from 180 mcg to 45 mg of K2 or 100 mcg to 5 mg of K1) and found vitamin K reduced the odds of clinical fractures (odds ratio 0.44, 95% CI 0.23-0.88, from 4 pooled studies) and vertebral fractures (odds ratio 0.42, 95% CI 0.27-0.66) [2]. On the cardiovascular side, a randomized controlled trial in hemodialysis patients, a population with severe vascular calcification, tested vitamin K2 against vascular calcification progression using serial imaging [3].
What the evidence does not show: in the same 2022 meta-analysis that found reduced fracture odds, the pooled effect on femoral neck bone mineral density was not statistically significant (95% CI -0.03 to 0.20, P=0.08), and the authors called the femoral BMD data "inconclusive." That is an uncomfortable mismatch: fewer fractures without a matching, statistically clean improvement in the bone density measurement that supposedly explains the mechanism. The review's own conclusion states plainly that vitamin K showed only a small impact on BMD despite the fracture signal, and calls for more studies before treating K2 as an established anti-osteoporotic therapy. On the cardiovascular side, most trials measuring arterial calcification directly are small, short relative to a process that unfolds over decades, and conducted in patients with kidney disease or other conditions that accelerate calcification, not in healthy adults trying to prevent it before symptoms appear.
No verified Blueprint product page lists a specific standing K2 dose as part of Bryan Johnson's protocol at the time of this review; where third-party sources cite a number, we have not been able to confirm it against an official Blueprint page, so no dose is attributed to him here.
Critics of the K2-for-arteries argument point out that matrix Gla protein carboxylation status is a biomarker, not a clinical outcome, and that no trial has yet shown that raising carboxylated MGP with K2 supplementation translates into fewer heart attacks or strokes in a general population. The mismatch between the fracture-reduction meta-analysis result and its own non-significant BMD finding is a good illustration of why a plausible mechanism and a positive endpoint in one meta-analysis still leave real uncertainty about the mechanism working as advertised.
The honest takeaway: K2 has a real biological role in calcium trafficking, some fracture-reduction signal in meta-analysis, and a bone-density result too weak to confirm the mechanism behind it.
Products with this: Vitamin K2
References
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