Vitamin K and bone metabolism in the elderly with normal and reduced kidney function

Vitamin K plays a key role in the synthesis of several blood coagulation factors, but it is also involved in bone metabolism and vascular calcification. There are two forms of vitamin K: K1 and K2, which may behave differently. Oral anticoagulation with warfarin inhibits the vitamin K system. Although warfarin reduces ischemic stroke, there are concerns on hemorrhagic complications and, due to the impaired activity of other vitamin K-dependent proteins such as osteocalcin (or BGP, bone Gla protein) and MGP (matrix Gla protein), on an increased burden of bone fractures and vascular calcifications. These in turn may be significant determinants of morbidity and mortality. The geriatric population, who is often affected by bone disorders frequently related to aging itself, could benefit from a supplementation of vitamin K, but further studies are necessary to prove actual benefits, both in CKD patients and in the general population. In patients at risk of vascular calcifications and fractures, in particular elderly patients affected by CKD, the possible beneficial role of vitamin K supplementation, as well as more a selected administration of vitamin K inhibitors for anticoagulation should be considered.