Effects of vitamin K on Calcium and bone metabolism
The term vitamin K is used for a family of naphthoquinones: the natural vitamins K1 and K2. […] Vitamin K1 is synthesized by plants. Menaquinone is a large family of vitamins K2 […] synthesized by bacteria.
The essentiality of vitamin K is dominantly defined by its role as a cofactor for the vitamin K-dependent carboxylase, an enzyme that is responsible for the post-translational conversion of the GLA residues in a limited number of proteins including osteocalcin. […]
Osteocalcin, the most abundant noncollagenous protein in bone, is produced by osteoblasts during bone matrix formation. The GLA residue, when it is carboxylated, binds the Calcium ions. If sufficient vitamin K is not available, some or all of the GLA residues are de-carboxylated. […] Epidemiological studies have demonstrated that elderly women with high circulating levels of undercarboxylated osteocalcin have an increased risk of hip fractures […]
Vitamin K supplementation leads to significant reductions of Calcium in urine […], suggesting a decrease in bone resorption. […] Vitamin K2 can influence differentiation and functions of bone marrow cells. Consequently, vitamin K2 can facilitate bone metabolism […] and modulate cellular differentiation and functions in bone marrow.
In recent literature there is evidence that vitamin K is an important modulating factor of bone physiology. […] Epidemiological studies demonstrate that both low vitamin K intake as well as unphysiological low biochemical parameters (e.g. undercarboxylated osteocalcin) are associated to an increased osteoporotic fracture risk. […] Age and hormone-related changes associated with menopause also influence the serum levels of undercarboxylated osteocalcin.
[…] There is, however, impressive evidence from Japanese research groups that very high pharmacological doses of vitamin K2 are able to prevent further bone weakening and also to reduce fracture risk.
Armin Zittermann: Effects of vitamin K on calcium and bone metabolism. Current Opinion in Clinical Nutrition and Metabolic Care.