title: A novel method based on curvature analysis for estimating the dietary vitamin K requirement in adolescents.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Hygienic Sciences, Kobe Pharmaceutical University, Kobe, Japan.
authors.forename: Naoko
authors.initials: N
authors.lastname: Tsugawa
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Uenishi
authors.forename: Hiromi
authors.initials: H
authors.lastname: Ishida
authors.forename: Takuya
authors.initials: T
authors.lastname: Minekami
authors.forename: Ayako
authors.initials: A
authors.lastname: Doi
authors.forename: Sayaka
authors.initials: S
authors.lastname: Koike
authors.forename: Tomoki
authors.initials: T
authors.lastname: Takase
authors.forename: Maya
authors.initials: M
authors.lastname: Kamao
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Mimura
authors.forename: Toshio
authors.initials: T
authors.lastname: Okano
mesh_terms: D000293:Adolescent; D015415:Biomarkers / Q000097:blood; D001777:Blood Coagulation / Q000502:physiology*; D001842:Bone and Bones / Q000378:metabolism / Q000502:physiology*; D002648:Child; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D009751:Nutritional Requirements; D009752:Nutritional Status; D015675:Osteocalcin / Q000097:blood; D011498:Protein Precursors / Q000097:blood; D011516:Prothrombin; D012044:Regression Analysis; D014812:Vitamin K / Q000008:administration & dosage* / Q000097:blood*
chemical_list: D015415:Biomarkers; D011498:Protein Precursors; D015675:Osteocalcin; D014812:Vitamin K; C008208:acarboxyprothrombin; D011516:Prothrombin