Update on the role of vitamin K in skeletal health

A protective role for vitamin K in bone health has been suggested based on its role as an enzymatic cofactor. In observational studies, vitamin K insufficiency is generally associated with lower bone mass and increased hip fracture risk. However, these findings are not supported in randomized controlled trials (RCT) of phylloquinone (vitamin K-1) supplementation and bone loss at the hip in the elderly. This suggests that increased vegetable and legume intakes may simultaneously improve measures of vitamin K status and skeletal health, even though the mechanisms underlying these improvements may be independent of each other. Menaquinone-4 (vitamin K-2), when given at pharmacological doses, appears to protect against fracture risk and bone loss at the spine. However, there are emerging data that suggest the efficacy of vitamin K supplementation on bone loss is inconclusive. (C) 2008 International Life Sciences Institute.