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 supplementation does not influence bone loss in early menopausal women: a randomised double-blind placebo-controlled trial
Summary Vitamin K2 may preserve bone strength and reduce fracture risk . In this r and omised double-blind placebo-controlled trial among healthy postmenopausal Norwegian women , 1 year supplementation of vitamin K2 in the form of Natto capsules had no effect on bone loss rates . Introduction Japanese studies indicate that vitamin K2 ( menaquinone-7 ( MK-7 ) ) intake may preserve bone strength , but this has not been documented in Europeans . The aim of this study was to assess the effect of MK-7 on bone mineral density ( BMD ) changes in postmenopausal Norwegian women . Methods Three hundred thirty-four healthy women between 50 and 60 years , 1–5 years after menopause , were recruited to a r and omised double-blind placebo-controlled trial . The participants were r and omly assigned into two groups , one receiving 360 µg MK-7 in the form of Natto capsules and the other the same amount of identical-looking placebo capsules containing olive oil . BMD was measured at total hip , femoral neck , lumbar spine and total body at baseline and 12 months together with serum levels of bone-specific alkaline phosphatase , Crosslaps , total osteocalcin ( N-mid OC ) , carboxylated ( cOC ) and under-carboxylated osteocalcin ( ucOC ) . Results After 12 months , there were no statistical differences in bone loss rates between the groups at the total hip or any other measurement site . Serum levels of cOC increased and ucOC decreased in the treatment versus the placebo group ( p < 0.001 ) . Conclusion MK-7 taken as Natto over 1 year reduced serum levels of ucOC but did not influence bone loss rates in early menopausal women
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 .