RESUMO
BACKGROUND & AIMS: Few studies have investigated the association between vitamin K status and bone health in adolescents. We established a novel method for estimating the vitamin K status in adolescents by curvature analysis using the serum concentrations of undercarboxylated osteocalcin (ucOC)-a sensitive biomarker of vitamin K status in the bone. We also compared the vitamin K concentrations required for good bone health and for normal blood coagulation. METHOD: We enrolled 1183 healthy adolescents. For the curvature analysis, we used a logarithmic regression equation obtained from vitamin K intake and serum ucOC or plasma abnormal prothrombin (PIVKA-II) concentrations (marker for blood coagulation). The cut-off point was determined to be the vitamin K intake that showed the highest curvature. RESULTS: In adolescents, the serum ucOC concentration was negatively correlated with vitamin K intake. In the curvature analysis, requirement of vitamin K intake for good bone health and normal blood coagulation were 155-188 µg/d and 62-54 µg/d [1 µg/(kg d)], respectively; the latter result was consistent with that of a previous report. CONCLUSION: Our novel method is useful for estimating the vitamin K status; moreover, this method showed that bone metabolism requires more vitamin K than blood coagulation.
