Dr. Kumar’s Take:
This study highlights a major gap in how we think about bone health. While most guidelines focus on bone density, this review emphasizes bone quality—collagen strength, protein activation, and flexibility. MK-7 (vitamin K2) outperforms K1 and MK-4 in activating osteocalcin and supporting healthy bone architecture, especially at nutritional doses. If you’re over 40 or at risk for fractures, MK-7 could be a smart addition to your daily routine.
Key Takeaways:
✔ MK-7 is more effective than vitamin K1 and MK-4 in activating osteocalcin at low doses.
✔ It supports bone strength by improving bone quality, not just bone mineral density.
✔ MK-7 from natto is highly bioavailable and has a long half-life in the body.
✔ Even doses well above the RDI appear to be safe and well-tolerated.
Actionable Tip:
Consider taking 180 - 375 µg/day of MK-7 (often found in natto or supplements) if you’re concerned about bone loss, especially if you’re postmenopausal or aging. It’s most effective when taken with a fat-containing meal.
Brief Summary:
This narrative review highlights the unique benefits of vitamin K2 as menaquinone-7 (MK-7) for bone strength. Unlike vitamin K1 and MK-4, MK-7 remains in the bloodstream longer and effectively activates extrahepatic vitamin K-dependent proteins (VKDPs), including osteocalcin. These proteins regulate calcium deposition and improve bone flexibility. Regular consumption of natto, a fermented soybean rich in MK-7, is linked to fewer hip fractures in Japanese populations. The review concludes that current RDIs based on blood clotting are insufficient for bone and cardiovascular health.
Study Design:
This was a narrative review published in Nutrients (2020) summarizing past research on the bioavailability, safety, and skeletal effects of MK-7. The authors compared different forms of vitamin K (K1, MK-4, MK-7), reviewed bone density and fracture studies, and analyzed MK-7’s role in activating VKDPs in both animal and human models.
Results:
- MK-7 significantly boosts carboxylation of osteocalcin and matrix Gla protein at doses of 90–180 µg/day.
- MK-7 improved bone strength in rats even when bone mineral density remained unchanged.
- Postmenopausal women taking MK-7 had reduced bone loss and increased bone quality.
- Natto intake was inversely associated with hip fracture risk, independent of bone density.
- MK-7 was safe even at doses as high as 600 µg/day for one month.
How MK-7 Works:
MK-7 helps activate osteocalcin, a protein made by osteoblasts that guides calcium into bones. It also influences collagen production, a major factor in bone flexibility and strength. Additionally, MK-7 may be converted into MK-4 in certain tissues and works through the SXR/PXR receptor pathway to influence gene expression and bone formation. Unlike MK-4, MK-7 stays active in the bloodstream longer and builds up more effectively in organs like bone and brain.
Related Studies and Research
Review of MK-7 supplementation effects on bone quality, including compression and impact strength metrics. – Summarizes mechanical improvements in bone with MK-7.
Three-year RCT evaluating low-dose MK-7’s impact on bone loss in healthy postmenopausal women. – Core trial on bone density preservation.
Investigates vitamin K2’s role in cartilage protection and GPX4 activation in osteoarthritis models. – Explores joint-protective antioxidant effects.
Examines the conversion efficiency of various dietary vitamin K forms into bioactive MK-4 in human tissues. – Tracks dietary K transformation to MK-4.
Discusses how vitamins D and K work together to support both bone density and cardiovascular protection. – Integrates D+K pathways in bone and vasculature.
Frequently Asked Questions
What foods contain MK-7?
Natto is the richest source, with 200–400 µg per serving. Other fermented foods like certain cheeses have smaller amounts.
How does MK-7 compare to MK-4?
MK-7 stays in the blood longer, is more bioavailable, and is effective at lower doses. MK-4 has a short half-life and may need higher pharmacological doses to achieve similar effects.
Is MK-7 safe?
Yes. Studies show even 600 µg/day is safe for at least one month. Long-term studies using 180 µg/day for 3 years found no major side effects.
Can I take MK-7 with warfarin?
No. MK-7 can interfere with blood-thinning medications like warfarin. Always consult your doctor first.
Conclusion
MK-7 (vitamin K2) plays a crucial role in bone health beyond what vitamin K1 or MK-4 can offer. Its superior absorption and ability to activate bone-supporting proteins make it a powerful tool for reducing fracture risk, improving bone quality, and supporting long-term skeletal health—especially as we age.