One-hundred-eight postmenopausal women (mean age, 55 years) were randomly assigned to receive, in double-blind fashion, one of the following for three years: 1) placebo, 2) a daily supplement containing 500 mg of calcium, 10 mg of zinc, 150 mg of magnesium, and 320 IU of vitamin D (MD group), or 3) the same nutrients as in the MD group, plus 1 mg/day of vitamin K1 (MDK group).
After three years, the elastic properties of the carotid artery (as determined by parameters such as compliance coefficient, distensibility coefficient, and pulse pressure) remained unchanged in the MDK group, but decreased in the MD and placebo groups (p<0.05 for each comparison between MDK and placebo). There were no significant differences between MD and placebo.
These results indicate that, in postmenopausal women taking calcium, zinc, magnesium, and vitamin D, supplementation with 1 mg/day of vitamin K1 for three years prevented a deterioration of the elastic properties of the carotid artery wall. Vitamin K plays a role in the synthesis of matrix-Gla Protein (MGP, which is a strong inhibitor of vascular calcification. A deficiency of vitamin K in vascular tissues results in the formation of inactive MGP, which is a potential risk factor for calcification. In observational studies, poor vitamin K status was associated with increased risk of both coronary artery calcification and coronary heart disease-related mortality. In addition, treatment of rats with the vitamin K antagonist warfarin resulted in calcification of arteries, an effect that has also been reported in observational studies in humans.
Adequate vitamin K status appears to be important not only for normal blood clotting function and bone metabolism, but also to maintain vascular health. Good food sources of vitamin K include green leafy vegetable, soybean oil, and olive oil.
Braam LAJLM, et al. Beneficial effects of vits D and K on the elastic properties of the vessel wall in postmenopausal women: a follow-up study. Thromb Haemost 2004;91:373-380.
Reprinted with exclusive permission of The Townsend Letter for Doctors & Patients Jul 2005.