Serum percentage undercarboxylated osteocalcin, a sensitive measure of vitamin K status, and its relationship to bone health indices in Danish girls

Recent cross-sectional data suggest that better vitamin K status in young girls (aged 3-16 years) is associated with decreased bone turnover, even though it is not associated with bone mineral content (BMC). The objective of the present study was to investigate the relationship between serum percentage of undercarboxylated osteocalcin (%ucOC), as an index of vitamin K status, and BMC and biochemical indices of bone turnover in peri-pubertal Danish girls. This peri-pubertal stage is a dynamic period of bone development, and as such, may represent an important window of opportunity for vitamin K status to modulate childhood bone health. Serum %ucOC and serum 25-hydroxyvitamin D (25 (OH) D) were measured at baseline in a study of 223 healthy girls aged 11-12 years. Urinary pyridinium crosslinks of collagen and serum total osteocalcin as markers of bone resorption and formation, respectively, as well as BMC (total body and lumbar spine) were also measured. Serum %ucOC (median 21.9%) was not associated with markers of bone resorption or with total osteocalcin. Serum %ucOC was inversely correlated with serum 25 (OH) D (r - 0.143; P<0.05). Serum %ucOC was negatively associated with BMC of the total body (β - 0.045; P<0.001) and lumbar spine (β - 0.055; P<0.05), after adjustment for potential confounders including vitamin D status. Better vitamin K status was associated with increased BMC, but not bone turnover, in healthy peri-pubertal Danish girls. There is a need for well-designed, randomized phylloquinone supplementation trials in children and adolescents to confirm epidemiological findings of an association between vitamin K status and bone health.