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 .
Dietary Vitamin K2 Supplement Improves Bone Status After Lung and Heart Transplantation
Background . Osteoporosis is a problem after transplantation . Studies since the last year indicate that vitamin K plays a role in optimal bone health . The aim of this r and omized , double blind , prospect i ve longitudinal study was to investigate the effect of a dietary supplement with vitamin K2 ( 180 μg menakinon-7 ) on bone mass , the first year after lung and heart transplantation . Methods . After preoperative baseline investigation of bone mass and bone-related biochemistry , 35 lung and 59 heart recipients were postoperatively r and omized to vitamin K2 or placebo and reinvestigated the following year . Results . In all recipients , 1 year after solid organ transplantation , the difference between vitamin K2 and placebo for the lumbar spine ( L2–L4 ) bone mineral density ( BMD ) was 0.028 ( SE 0.014 ) g/cm2 , P=0.055 and for L2 to L4 bone mineral content was 1.33 ( SE 1.91 ) g/cm2 ( P=0.5 ) . In lung recipients separately , the difference for bone mineral content was 3.39 g ( SE 1.65 ) , P=0.048 and in heart recipients 0.45 ( SE 0.02 ) g , P=0.9 after controlling for baseline measures . In a forward stepwise linear regression analysis fitted to model differences in the L2 to L4 BMD , controlled for possible confounding variables ( including use of bisphosphonate ) , and the only significant predictors were organ ( B=−0.065 g/cm2 , P<0.001 ) and vitamin K2 ( B=0.034 g/cm2 , P=0.019 ) . Insufficient vitamin D status was common , and the parathyroid hormone was highest in the K2 group indicating a higher need for vitamin D. Conclusions . One year of vitamin K2 supplement suggest a favorable effect on lumbar spine BMD with different response in lung and heart recipients . Vitamin D status should receive more attention
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 .