Oral high-dose vitamin K2 (menaquinone-4, 45 mg/d) has been approved for the treatment of osteoporosis in Japan since 1995, and Cockayne and colleagues1 recently provided a meta-analysis of randomized controlled trials investigating the effects of vitamin K therapy on fracture risk. This analysis showed the strong effect of high-dose vitamin K2 on fracture prevention among Japanese patients. There is no evidence that vitamin K has extraskeletal effects on fracture risk, indicating that this vitamin would restrict bone fragility, which depends on its quantity and quality.2 However, the mechanisms by which vitamin K reduces fracture incidence have been poorly understood.
Sugiyama T. Possible Involvements of Vitamin K in Bone Quality. Arch Intern Med. 2007;167(1):93-94. doi:10.1001/archinte.167.1.93