Effect of vitamin K supplementation on insulin resistance in older men and women.
OBJECTIVE
Vitamin K has a potentially beneficial role in insulin resistance, but evidence is limited in humans. We tested the hypothesis that vitamin K supplementation for 36 months will improve insulin resistance in older men and women.


METHODS
This was an ancillary study of a 36-month, randomized, double-blind, controlled trial designed to assess the impact of supplementation with 500 microg/day phylloquinone on bone loss. Study participants were older nondiabetic men and women (n = 355; aged 60-80 years; 60% women). The primary outcome of this study was insulin resistance as measured by homeostasis model assessment (HOMA-IR) at 36 months. Fasting plasma insulin and glucose were examined as the secondary outcomes.


RESULTS
The effect of 36-month vitamin K supplementation on HOMA-IR differed by sex (sex x treatment interaction P = 0.02). HOMA-IR was statistically significantly lower at the 36-month visit among men in the supplement group versus the men in the control group (P = 0.01) after adjustment for baseline HOMA-IR, BMI, and body weight change. There were no statistically significant differences in outcome measures between intervention groups in women.


CONCLUSIONS
Vitamin K supplementation for 36 months at doses attainable in the diet may reduce progression of insulin resistance in older men.
Yoshida
Makiko
M
Jean Mayer US Department of Agriculture, Human Nutrition Research Center, Tufts University, Boston, Massachusetts, USA.
Jacques
Paul F
PF
Meigs
James B
JB
Saltzman
Edward
E
Shea
M Kyla
MK
Gundberg
Caren
C
Dawson-Hughes
Bess
B
Dallal
Gerard
G
Booth
Sarah L
SL
D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D019587:Dietary Supplements; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007333:Insulin Resistance; D008297:Male; D008875:Middle Aged; D012737:Sex Factors; D016896:Treatment Outcome; D014812:Vitamin K / Q000008:administration & dosage*; D014815:Vitamins / Q000008:administration & dosage
D014815:Vitamins; D014812:Vitamin K