Summary Vitamin K may affect  bone mineral density and fracture incidence .
Since publication of a previous systematic review the integrity of some of the previous evidence has been question ed and further trials have been published .
Introduction This systematic review was design ed to assess the effectiveness of oral vitamin K supplementation for increasing bone mineral density  and reducing fractures in adults .
Vitamin K2 (menaquinone-7) prevents age-related deterioration of trabecular bone microarchitecture at the tibia in postmenopausal women.
OBJECTIVE Clinical studies suggest that vitamin K2 protects against bone loss and fractures ; however , its effect on bone quality has never been investigated . We investigated the effect of vitamin MK-7 on undercarboxylated osteocalcin ( ucOC ) , and bone mass and quality . DESIGN We conducted a r and omised , placebo-controlled , double-blinded clinical trial . METHODS We investigated the effect of MK-7 375 µg for 12 months on bone mineral density ( BMD ) measured by dual X-ray absorptiometry ( DXA ) , bone microarchitecture measured by high-resolution peripheral quantitative computed tomography ( HRpQCT ) and biochemical bone turnover markers in 148 postmenopausal women with osteopenia . All of them were supplemented with calcium and vitamin D.  RESULTS ucOC decreased in the MK-7 group ( -65.6 ( 59.1 ; 71.0 ) % ) ( median ( CI ) ) compared with the placebo group ( -6.4 ( -13.5 ; 1.2 ) % ) after 3 months ( P < 0.01 ) . HRpQCT after 12 months demonstrated that trabecular number in tibia was unchanged in the MK-7-group ( -0.1 ± 1.9 % ) ( mean ± s.d . ) and decreased in the placebo group ( -3.5 ± 2.2 % ) , trabecular spacing was unchanged in the MK-7 group ( + 1.2 ± 8.0 % ) and increased in the placebo group ( + 4.5 ± 9.7 % ) , and trabecular thickness was unchanged in the MK-7 group ( + 0.2 ± 1.7 % ) and increased in the placebo group ( + 4.0 ± 2.2 % ) ( between-group changes for all : P < 0.05 ) . There were no significant differences between the groups in HRpQCT-derived parameters at the radius or in BMD at any site . CONCLUSION The changes in bone microarchitecture in the placebo group are consistent with the age-related deterioration of trabecular structure , with a loss of trabeculae and a greater mean thickness of the remaining trabeculae . This suggests that vitamin MK-7 preserves trabecular bone structure at the tibia
Summary Vitamin K may affect  bone mineral density and fracture incidence .
Since publication of a previous systematic review the integrity of some of the previous evidence has been question ed and further trials have been published .
Introduction This systematic review was design ed to assess the effectiveness of oral vitamin K supplementation for increasing bone mineral density  and reducing fractures in adults .