Vitamin K status of healthy Japanese women: Age-related vitamin K requirement for γ-carboxylation of osteocalcin

Naoko Tsugawa, Masataka Shiraki, Yoshitomo Suhara, Maya Kamao, Kiyoshi Tanaka, Toshio Okano

Research output: Contribution to journalArticlepeer-review

94 Citations (Scopus)


Background: Vitamin K deficiency is associated with low bone mineral density and increased risk of bone fracture. Phylloquinone (K1) and menaquinone 4 (MK-4) and 7 (MK-7) are generally observed in human plasma; however, data are limited on their circulating concentrations and their associations with bone metabolism or with γ-carboxylation of the osteocalcin molecule. Objectives: The objectives were to measure the circulating concentrations of K1, MK-4, and MK-7 in women and to ascertain whether each form of vitamin K is significantly associated with bone metabolism. Design: Plasma concentrations of K1, MK-4, MK-7, undercarboxylated osteocalcin (ucOC; measured by using the new electrochemiluminescence immunoassay), intact osteocalcin (iOC), calcium, and phosphorus; bone-derived alkaline phosphatase activity; and concentrations of urinary creatinine, N-terminal telopeptide, and deoxypyridinoline were measured in healthy women (n = 396). Results: On average, MK-7 and MK-4 were the highest and lowest, respectively, of the 3 vitamers in all age groups. K1 and MK-7 correlated inversely with ucOC, but associations between nutritional basal concentration of MK-4 and ucOC were not observed. Multiple regression analysis indicated that not only K1 and MK-7 concentrations but also age were independently correlated with ucOC concentration and the ratio of ucOC to iOC. The plasma K1 or MK-7 concentration required to minimize the ucOC concentration was highest in the group aged ≥70 y, and it decreased progressively for each of the younger age groups. Conclusions: The definite role of ucOC remains unclear. However, if submaximal γ-carboxylation is related to the prevention of fracture or bone mineral loss, circulating vitamin K concentrations in elderly people should be kept higher than those in young people.

Original languageEnglish
Pages (from-to)380-386
Number of pages7
JournalAmerican Journal of Clinical Nutrition
Issue number2
Publication statusPublished - 2006 Feb 1
Externally publishedYes


  • Bone turnover makers
  • Healthy elderly women
  • Menaquinone 4
  • Menaquinone 7
  • Osteocalcin
  • Phylloquinone
  • Plasma concentrations
  • Vitamin K

ASJC Scopus subject areas

  • Medicine (miscellaneous)
  • Nutrition and Dietetics


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