November 2008
Makiko Yoshida, PHD, Paul F. Jacques, SCD, James B. Meigs, MD, MPH, Edward Saltzman, MD, M. Kyla Shea, PHD, Caren Gundberg, PHD, Bess Dawson-Hughes, MD, Gerard Dallal, PHD, and Sarah L. Booth, PHD
Abstract
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.
RESEARCH DESIGN AND METHODS—This was an ancillary study of a 36-month, randomized, double-blind, controlled trial designed to assess the impact of supplementation with 500 μg/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 × 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.
