A high phylloquinone intake is required to achieve maximal osteocalcin gamma-carboxylation.
BACKGROUND
Dietary vitamin K is usually inadequate to maximize serum osteocalcin gamma-carboxylation. Phylloquinone supplementation increases osteocalcin gamma-carboxylation; however, the amount required to maximize carboxylation is not known.


OBJECTIVE
This study assessed the ability of various doses of phylloquinone (vitamin K(1)) to facilitate osteocalcin gamma-carboxylation.


METHODS
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 micro g 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 gamma-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 micro g/d) for 2 wk (substudy B). The percentage of undercarboxylated osteocalcin (%ucOC) was measured at baseline and weeks 1 and 2.


RESULTS
In substudy A, %ucOC decreased with phylloquinone supplementation (P < 0.0001); a greater reduction was observed with 1000 and 2000 micro g than with 500 micro g (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- micro g and the placebo groups and between the 1000- and 500- micro g groups but not between the 250-, 375-, and 500- micro g groups.


CONCLUSIONS
A daily phylloquinone intake of approximately 1000 micro g is required to maximally gamma-carboxylate circulating osteocalcin.
Binkley
Neil C
NC
Institute on Aging, Department of Medicine, University of Wisconsin, Madison, USA. nbinkley@facstaff.wisc.edu
Krueger
Diane C
DC
Kawahara
Tisha N
TN
Engelke
Jean A
JA
Chappell
Richard J
RJ
Suttie
John W
JW
D000328:Adult; D019587:Dietary Supplements; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D008297:Male; D015675:Osteocalcin / Q000378:metabolism*; D010837:Vitamin K 1 / Q000008:administration & dosage* / Q000494:pharmacology
D015675:Osteocalcin; D010837:Vitamin K 1