ARS | Publication request: Effect of Vitamin K Supplementation on Insulin Resistance in Older Men and Women

Submitted to: Diabetes Care
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 6, 2008
Publication Date: December 1, 2008
Citation: Yoshida, M., Jacques, P., Meigs, J., Saltzman, E., Shea, K., Gundberg, C., Dawson-Hughes, B., Dallal, G., Booth, S.L. 2008. Effect of Vitamin K Supplementation on Insulin Resistance in Older Men and Women. Diabetes Care. 31:2092-2096.

Interpretive Summary: Vitamin K is an important nutrient in blood clotting. Recent evidence suggests a potential new role of vitamin K and diabetes. In 355 non-diabetic healthy older adults (60-80 y), we looked to see if 36-month supplementation of vitamin K at intakes attainable in the diet has an influence on the age-related reduction of insulin action. Study participants were randomly divided into two groups. One group supplemented with vitamin D, calcium, and multivitamins, as a standard treatment, and the other group received vitamin K supplement in addition to the standard treatment. We found the impact of vitamin K supplementation on insulin action differs between men and women. Vitamin K supplementation had a preventive effect on age-related deterioration of insulin action in older men, but this beneficial effect was not observed in older women. Our findings support a potential beneficial role of vitamin K in the efficiency of insulin action in older men. However, the present study was based on the available data from a clinical trial that assessed effect of vitamin K supplementation on bone loss. Therefore, our findings need to be re-examined by the studies which designed for assessing the effect of vitamin K on insulin action.

Technical Abstract: Previous studies have suggested a potentially beneficial role for vitamin K on insulin resistance, but this has not been examined in a randomized controlled trial. We tested the hypothesis that vitamin K supplementation for 36 months will improve insulin resistance in older men and women. This is an ancillary study of a 36-month, randomized, double-blind, controlled trial designed to assess the impact of supplementation with 500 microgram/d of phylloquinone on age-related bone loss. Study participants were older, non-diabetic men and women (n = 355; 60-80 y; 60% women). The primary outcome was insulin resistance, measured by the homeostasis model (HOMA-IR) assessed at baseline, 6 and 36 months. Fasting plasma insulin and glucose were examined as the secondary outcomes. The effect of vitamin K supplementation on HOMA-IR at the 36-month visit differed by sex (sex-by-treatment interaction: P = 0.02). HOMA-IR was statistically significantly lower at the 36-month visit among men in the supplement group vs. 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. Vitamin K supplementation for 36 months at doses attainable in the diet may have a beneficial effect on insulin resistance in older men.