VITAMIN-K NUTRITION AND OSTEOPOROSIS

Although the abundance of vitamin K-dependent proteins in bone suggest s an important function, the precise role of vitamin K in skeletal hea lth remains to be determined. Serum concentrations of vitamin K are re portedly reduced in older individuals and persons with osteoporotic fr acture. Whether this is causally related to vitamin K insufficiency or simply reflects inadequate nutritional status is unclear. Circulating levels of undercarboxylated osteocalcin may be a sensitive marker of vitamin K inadequacy and have been reported to be increased in both po stmenopausal women and individuals who sustain hip fracture. It is als o possible that vitamin K indirectly affects the skeleton via control of renal calcium excretion. The effect of vitamin K antagonists (oral anticoagulants) on both renal calcium excretion and bone density is co ntroversial. Thus, many of the reports implicating a role for vitamin K insufficiency in the development of osteoporosis are conflicting. Th is review summarizes current knowledge regarding a possible role of vi tamin K insufficiency in the pathogenesis of osteoporosis.