Dietary phylloquinone depletion and repletion in older women.
Biological markers indicative of poor vitamin K status have been associated with a greater risk for hip fracture in older men and women. However, the dietary phylloquinone intake required to achieve maximal carboxylation of hepatic and extrahepatic vitamin K-dependent proteins is not known. In an 84-d study in a metabolic unit, 21 older (60-80 y) women were fed a phylloquinone-restricted diet (18 micro g/d) for 28 d, followed by stepwise repletion of 86, 200 and 450 micro g/d of phylloquinone. Plasma phylloquinone, urinary gamma-carboxyglutamic acid excretion and gamma-carboxylation of hepatic (prothrombin) and extrahepatic proteins (osteocalcin) decreased in response to phylloquinone restriction (P < 0.001), demonstrating the production of subclinical vitamin K deficiency. The gamma-carboxylation of prothrombin was restored to normal levels in response to phylloquinone supplementation at 200 micro g/d. In contrast, all other biochemical markers of vitamin K status remained below normal levels after short-term supplementation of up to 450 micro g/d of phylloquinone. These data support previous observations in rats that hepatic vitamin K-dependent proteins have preferential utilization of phylloquinone in response to phylloquinone dietary restriction. Moreover, our findings suggest that the current recommended Adequate Intake levels of vitamin K (90 micro g/d) in women do not support maximal osteocalcin gamma-carboxylation in older women.
Booth
Sarah L
SL
Jean Mayer U.S. Department of Agriculture Human Nutrition Research Center on Aging at Tufts University, Boston, MA 02111, USA. sarah.booth@tufts.edu
Martini
Ligia
L
Peterson
James W
JW
Saltzman
Edward
E
Dallal
Gerard E
GE
Wood
Richard J
RJ
D015055:1-Carboxyglutamic Acid / Q000652:urine; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000378:metabolism*; D004032:Diet / Q000009:adverse effects*; D005260:Female; D006801:Humans; D008099:Liver / Q000378:metabolism; D008875:Middle Aged; D011516:Prothrombin / Q000378:metabolism; D010837:Vitamin K 1 / Q000097:blood / Q000378:metabolism* / Q000494:pharmacology*
D015055:1-Carboxyglutamic Acid; D010837:Vitamin K 1; D011516:Prothrombin