The effect of menaquinone-7 (vitamin K2) supplementation on osteocalcin carboxylation in healthy prepubertal children (van Summeren MJ et al.)

Vitamin K contributes to bone health, probably through its role as cofactor in the carboxylation of osteocalcin. Intervention studies in adults have demonstrated that markedly higher osteocalcin carboxylation is obtained by intakes of vitamin K well above the current recommended dietary intake. However, the relationship between increased vitamin K2 intake and enhanced osteocalcin carboxylation had not been shown in healthy children. To that end, researchers conducted a study of the effect of 45 micrograms of vitamin K2 as menaquinone-7 (MK-7)) on the circulating levels of undercarboxylated osteocalcin (ucOC) and carboxylated osteocalcin (cOC) in healthy prepubertal children.

The researchers hypothesised that MK-7 supplementation will reduce the ucOC:cOC ratio (UCR), indicating an improved vitamin K status. The double-blind, randomized, placebo-controlled trial examined the effect of 8 weeks MK-7 supplementation on the carboxylation of osteocalcin in healthy children (n = 55). Serum levels of ucOC, cOC, and MK-7 were measured at baseline and after 8 weeks, together with bone markers and coagulation parameters. The UCR was used as an indicator of vitamin K status.

In the MK-7-supplemented group (n 28), the circulating concentration of inactive ucOC reduced and the UCR improved whereas the concentration of MK-7 increased. Within the placebo group, ucOC, cOC, UCR, and MK-7 did not significantly change over time. In both groups, bone markers and coagulation parameters remained constant over time.

The researchers concluded that these findings demonstrate that in healthy, prepubertal children, modest supplementation with MK-7 increases circulating concentrations of MK-7 as well as increases in osteocalcin carboxylation.

Reference: van Summeren MJ et al. The effect of menaquinone-7 (vitamin K2) supplementation on osteocalcin carboxylation in healthy prepubertal children. Br J Nutr. 2009 Oct;102(8):1171-8.

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