Bone Abstracts

Background: Clinical studies suggest that vitamin K2 prevents bone loss and may protect against fractures. Vitamin K is a cofactor in the carboxylation of Osteocalcin (OC). Carboxylated OC promotes mineralization of bone. The aim of the study was to investigate the effect of vitamin K2 on osteocalcin, bone mass and -quality.

Methods: We conducted a randomized placebo-controlled double-blinded clinical trial, in which 142 postmenopausal osteopenic women were treated with vitamin K2 (375 μg MK-7) or placebo. Both groups received vitamin D3 (38 μg/day) and calcium (800 mg/day). We measured bone markers and bone mineral density and -quality by DXA and HRpQCT. All results are given as changes after 12 months.

Results: Microarchitecture at the tibia changed differently between the groups; Trabecular number remained stable in the MK-7-group (−0.6±8.2%), but decreased in the placebo-group (−3.5±8.6%) (P=0.04), trabecular spacing did not change in the MK-7-group (1.2±8.0%) but increased in the placebo-group (4.5±9.7%)(P=0.03), and trabecular thickness was unaltered in the MK-7-group (+0.7±7.7%) but increased in the placebo-group (+4.0±8.7%) (P=0.02). Changes in microarchitecture in radius did not differ between groups.

Changes in aBMD did not differ between groups at either the lumbar spine or total hip (P=0.23 and P=0.42).

Undercarboxylated osteocalcin decreased in the MK-7-group (−65.2±23.5%) compared to the placebo-group (−0.03±38.5%) (P<0.01). Total OC decreased in the MK-7-group (−18.8±13.9%) compared placebo-group (−2.5±12.8%)(P<0.01). BAP increased in the MK-7-group (+4.1±13.7%) compared to the placebo-group (−1.3±12.7%) (P=0.02). Changes in P1NP and CTX did not differ between groups (P>0.5).

Conclusion: The change in undercarboxylated OC suggests increasing carboxylation of OC, which may indicate increased mineralization of bone. HRpQCT results suggest that vitamin MK-7 may prevent the age-related loss of trabeculae. However, there is no difference in changes in BMD. There is need for long-term investigations of the effect of vitamin K2 on bone.