Vitamin K2 MK-7 Slows Bone Density Decline in 3-Year Postmenopausal Trial
Vitamin K2 directs calcium to settle in bones. Even with adequate calcium intake, K2 deficiency can cause calcium to accumulate in artery walls instead. Among K2 forms, MK-7 (menaquinone-7) has a half-life of approximately 72 hours, enabling stable blood levels with once-daily dosing.
A 3-year randomized controlled trial registered on PubMed measured MK-7 effects in 142 postmenopausal women with osteopenia (reduced bone density that has not yet reached osteoporosis).
Trial design
The 142 participants were divided into two groups.
- K2 group: MK-7 375mcg + vitamin D3 + calcium (daily, 3 years)
- Control group: placebo + vitamin D3 + calcium (daily, 3 years)
Both groups received vitamin D3 and calcium as baseline supplementation. The only variable was MK-7 addition.
Results
The K2 group showed a significant increase in lumbar spine bone mineral density (BMD). The control group experienced natural bone density decline over 3 years, while the K2 group showed attenuation of this decline. MK-7 effectively slowed the rate of age-related bone mineral density loss.
MGP, the calcium traffic controller
The key pathway through which K2 supports bone density involves matrix Gla protein (MGP). MGP is a vitamin K-dependent protein that, when activated, prevents calcium from depositing in blood vessels and soft tissues. Without sufficient K2, MGP remains inactive and vascular calcification progresses.
An intriguing finding is that MGP also exists in skin elastic fibers. The link between skin elasticity and K2 is still in early research stages, but the possibility that calcification prevention may also contribute to maintaining skin elasticity has been raised.
Dosage and food sources
- Standard MK-7 dose: 100 to 200mcg per day (this trial used 375mcg, which is on the higher end)
- Natto: approximately 1,000mcg per 100g, the richest food source
- Aged cheeses: 15 to 75mcg per 100g (Gouda, Brie)
- Egg yolks: approximately 15 to 30mcg per yolk
- For absorption: take with a fat-containing meal (K2 is fat-soluble)
If already taking a multivitamin or calcium supplement, check whether it contains K2 and which form (MK-4 versus MK-7) before adding more.
Why this matters for postmenopausal women
Estrogen decline after menopause accelerates bone density loss. Vitamin D3 and calcium are baseline supplements, but K2 adds precision by directing calcium to its intended destination. This 3-year trial demonstrates that when D3 plus calcium alone is insufficient, adding K2 produces a significant difference.
FAQ
Q. What is the difference between vitamin K2 and K1?
K1 (phylloquinone) primarily supports blood clotting and is found in green leafy vegetables. K2 (menaquinone) directs calcium to bones and removes it from blood vessels. Among K2 forms, MK-7 has a long half-life of approximately 72 hours, allowing once-daily dosing to maintain stable blood levels.
Q. Should I take vitamin K2 with vitamin D?
Vitamin D3 promotes calcium absorption, while K2 directs the absorbed calcium to settle in bones. In this trial, both groups received D3 and calcium as baseline, and the K2 addition group showed bone density improvement. D3 plus K2 is the standard combined approach.
Q. How much natto do I need to eat?
Natto contains approximately 1,000mcg of MK-7 per 100g, making it the richest food source. About 50g daily (roughly one pack) provides around 500mcg, well above clinical doses. For those who find natto difficult to consume, MK-7 supplements at 100 to 200mcg are the standard alternative.