A high phylloquinone intake is required to achieve maximal osteocalcin γ-carboxylation1,2,3

• Published in: The American journal of clinical nutrition Vol. 76; no. 5; pp. 1055 - 1060
• Main Authors: Binkley, Neil C, Krueger, Diane C, Kawahara, Tisha N, Engelke, Jean A, Chappell, Richard J, Suttie, John W
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.11.2002
• Subjects: osteocalcin; phylloquinone; undercarboxylated osteocalcin; Vitamin K; γ-carboxylation; undercarboxylated osteocalcin; phylloquinone; osteocalcin; γ-carboxylation; Vitamin K
• ISSN: 0002-9165; 1938-3207
• DOI: 10.1093/ajcn/76.5.1055

Dietary vitamin K is usually inadequate to maximize serum osteocalcin γ-carboxylation. Phylloquinone supplementation increases osteocalcin γ-carboxylation; however, the amount required to maximize carboxylation is not known. This study assessed the ability of various doses of phylloquinone (vitamin K1) to facilitate osteocalcin γ-carboxylation. Healthy adults aged 19–36 y participated in 2 substudies. In an initial dose-finding study (substudy A), 6 women and 4 men received a placebo daily for 1 wk and then phylloquinone daily for 3 wk: 500, 1000, and 2000 μg during weeks 2, 3, and 4, respectively. Osteocalcin and undercarboxylated osteocalcin were measured at baseline and after each week of supplementation. Subsequently, to further delineate the γ-carboxylation response of osteocalcin to various doses of vitamin K, 58 women and 42 men were randomly assigned to receive placebo or phylloquinone supplementation (250, 375, 500, and 1000 μg/d) for 2 wk (substudy B). The percentage of undercarboxylated osteocalcin (%ucOC) was measured at baseline and weeks 1 and 2. In substudy A, %ucOC decreased with phylloquinone supplementation (P < 0.0001); a greater reduction was observed with 1000 and 2000 μg than with 500 μg (P < 0.05). In substudy B, %ucOC decreased in all supplemented groups by week 1 (P for the trend < 0.0001), which was sustained through week 2. Phylloquinone supplementation decreased %ucOC dose-dependently; %ucOC was significantly different between the 250-μg and the placebo groups and between the 1000- and 500-μg groups but not between the 250-, 375-, and 500-μg groups. A daily phylloquinone intake of ≈1000 μg is required to maximally γ-carboxylate circulating osteocalcin.