The association of vitamin K with bone mineral density has been reported in some previous cohort studies and intervention studies. In cohort studies, higher vitamin K1 intake was associated with lower fracture incidence. Some intervention studies have described that vitamin K1 and vitamin K2 (menaquinone-4 : MK-4) supplementation were modestly efficacious in preventing fracture, but not in preserving bone mass. Although dietary reference intake (adequate intake : AI) for vitamin K was increased from previous value, current AI was determined as the dose sufficient to maintain normal blood coagulation with little mentioning to bone. Vitamin K intake greater than the current AI would be required for the bone health.