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 .
Serum undercarboxylated osteocalcin is a marker of the risk of hip fracture in elderly women.
It has been previously shown that the level of circulating undercarboxylated osteocalcin ( ucOC ) is elevated in elderly women in comparison with young , healthy , premenopausal ones . To underst and the mechanism of the increase in the ucOC in the elderly and to assess its potential consequences on bone fragility , we have measured  ucOC  in the sera of 195 elderly institutionalized women 70 - 101 yr of age . In 45 women ( 23 % ) serum ucOC was above the upper limit of the normal range for young women . The level of ucOC was negatively correlated with 25OHD ( r = -0.32 , P < 0.001 ) even after excluding the effect of age , parathyroid hormone ( PTH ) , and creatinine by partial correlation ( r = -0.24 , P < 0.002 ) . During an 18-mo follow-up , 15 women sustained a hip fracture and their baseline ucOC level was higher ( P < 0.01 ) in women who subsequently sustained hip fracture than in the nonfracture group contrasting with no significant differences for serum calcium , phosphate , alkaline phosphatase , creatinine , PTH , 250HD , and total and carboxylated OC . The risk of hip fracture was increased in women with elevated ucOC ( relative ratio 5.9 , 99.9 % Cl 1.5 - 22.7 , P < 0.001 ) . During 1 yr of calcium/vitamin D2 treatment , ucOC decreased ( P < 0.05 ) , especially in those with the initially increased values ( from 2.22 + /- 0.35 to 1.41 + /- 0.29 ng/ml , P < 0.005 ) contrasting with an increase in the placebo group ( P < 0.05 ) . In conclusion , the increase in ucOC in the elderly reflects not only some degree of vitamin K deficiency but also their poor vitamin D status , suggesting that vitamin D may be important , either directly or indirectly through its effect on bone turnover , for achieving a normal gamma-carboxylation of OC . The ucOC , but not conventional calcium metabolism parameters , predicts the subsequent risk of hip fracture , suggesting that serum ucOC reflects some changes in bone matrix associated with increased fragility
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 .