Vitamin K2 Supplement Guide: Bone Density Maintenance and Arterial Calcification Prevention

Vitamin K has two main forms: K1 (phylloquinone) and K2 (menaquinone). K1 is primarily involved in blood clotting and is found abundantly in green and yellow vegetables. K2 includes both body-converted K1 and forms found in fermented foods (natto, cheese), though dietary intake tends to be low. Among K2 forms, MK-7 (menaquinone-7) has a longer plasma half-life (~72 hours) than MK-4, allowing smaller amounts to act throughout the body for longer, making it increasingly popular as a supplement.

~72 hours

Plasma half-life of MK-7

Vitamin K2's primary bone action is promoting the carboxylation (activation) of osteocalcin, a bone protein. Activated osteocalcin helps incorporate calcium into the bone matrix, contributing to bone mineral density maintenance. An RCT by Knapen et al. (2013) found that postmenopausal women taking MK-7 180 µg/day for 3 years showed significantly attenuated bone mineral density decline at the lumbar spine and femoral neck compared to placebo. The combination with vitamin D is important: vitamin D absorbs calcium in the intestine while K2 directs that calcium into bone.

3 years

Follow-up period in key RCT

244 participants

Sample size in key RCT

When calcium is not properly regulated, it can deposit in blood vessel walls, contributing to arterial calcification (a factor in atherosclerosis). Vitamin K2 activates Matrix Gla Protein (MGP), which inhibits calcium deposition in blood vessels. In the aforementioned RCT, the MK-7 group showed attenuated progression of carotid arterial stiffness compared to placebo. The role of 'keeping calcium in bones and away from blood vessels' is one reason vitamin K2 attracts attention.

Research commonly uses 90–180 µg/day (in MK-7 form); one pack of natto (50g) contains approximately 200–400 µg of K2. An important precaution: those taking warfarin (anticoagulant) must consult a physician or pharmacist before use, as vitamin K affects warfarin's action. Combination with vitamin D3 is common in research, and combined effects are expected to exceed those of either alone. As a fat-soluble vitamin, absorption improves when taken with dietary fat.

90–180 µg/day

MK-7 dose commonly used in research