Vitamin K Supplementation in Post-Menopausal Osteopenia

Osteoporosis is major cause of morbidity and mortality in Canadian postmenopausal women. It is a systemic disease characterized by low bone mass and deterioration of bone microarchitecture, resulting in bone fragility and an increased risk of fractures. One in six women over the age of 50 have osteoporosis. The lifetime risk of an osteoporotic fracture for an average 50 year-old Canadian woman is \>40%. The annual health care costs for osteoporotic fractures in Canada have been estimated to exceed $1.3 billion. Recent data suggest that vitamin K supplements may decrease bone loss and prevent fractures. Vitamin K is a co-factor of gamma-glutamyl carboxylase, an enzyme that catalyzes the gamma-carboxylation of glutamic acid residues in bone matrix proteins such as osteocalcin. Vitamin K has been reported to enhance bone formation in both in vitro studies and in vivo studies in animals. Vitamin K levels are low in individuals with osteoporosis and in patients with osteoporotic fractures. The few studies examining vitamin K supplementation in humans have showed promising results with no significant side effects, but these studies had significant methodological shortcomings such as inadequate sample size and lack of randomization. The primary objective of our study is to examine whether vitamin K supplementation will increase bone mineral density in postmenopausal women with osteopenia. Our secondary objectives are to examine the possible adverse effects from long-term vitamin K supplementation, to investigate whether vitamin K will decrease risk of fractures and to determine if vitamin K affects quality of life. Our hypotheses are that vitamin K increases bone mineral density in postmenopausal women, and that there are no significant adverse effects from vitamin K supplementation.