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 K Supplementation in Postmenopausal Women with Osteopenia (ECKO Trial): A Randomized Controlled Trial
Background Vitamin K has been widely promoted as a supplement for decreasing bone loss in postmenopausal women , but the long-term benefits and potential harms are unknown . This study was conducted to determine whether daily high-dose vitamin K1 supplementation safely reduces bone loss , bone turnover , and fractures . Methods and Findings This single-center study was design ed as a 2-y r and omized , placebo-controlled , double-blind trial , extended for earlier participants for up to an additional 2 y because of interest in long-term safety and fractures . A total of 440 postmenopausal women with osteopenia were r and omized to either 5 mg of vitamin K1 or placebo daily . Primary outcomes were changes in BMD at the lumbar spine and total hip at 2 y. Secondary outcomes included changes in BMD at other sites and other time points , bone turnover markers , height , fractures , adverse effects , and health-related quality of life . This study has a power of 90 % to detect 3 % differences in BMD between the two groups . The women in this study were vitamin D replete , with a mean serum 25-hydroxyvitamin D level of 77 nmol/l at baseline . Over 2 y , BMD decreased by −1.28 % and −1.22 % ( p = 0.84 ) ( difference of −0.06 % ; 95 % confidence interval [ CI ] −0.67 % to 0.54 % ) at the lumbar spine and −0.69 % and −0.88 % ( p = 0.51 ) ( difference of 0.19 % ; 95 % CI −0.37 % to 0.75 % ) at the total hip in the vitamin K and placebo groups , respectively . There were no significant differences in changes in BMD at any site between the two groups over the 2- to 4-y period . Daily vitamin K1 supplementation  increased serum vitamin K1 levels by 10-fold , and decreased the percentage of undercarboxylated osteocalcin and total osteocalcin levels ( bone formation marker ) . However , C-telopeptide levels ( bone resorption marker ) were not significantly different between the two groups . Fewer women in the vitamin K group had clinical fractures ( nine versus 20 , p = 0.04 ) and fewer had cancers ( three versus 12 , p = 0.02 ) . Vitamin K supplements  were well-tolerated over the 4-y period . There were no significant differences in adverse effects or health-related quality of life between the two groups . The study was not powered to examine fractures or cancers , and their numbers were small . Conclusions Daily 5 mg of vitamin K1 supplementation for 2 to 4 y does not protect against age-related decline in BMD , but may protect against fractures and cancers in postmenopausal women with osteopenia . More studies are needed to further examine the effect of vitamin K on fractures and cancers . Trial registration : Clinical Trials.gov ( # NCT00150969 ) and Current Controlled Trials ( # IS RCT N61708241
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 .