Vitamin K may play a role in the pathogenesis of vascular calcification, as well as age-related bone loss. Epidemiological evidence has shown associations between the vitamin K-dependent protein, Matrix Gla Protein (MGP) and vascular calcification. Biochemical markers of vitamin K nutrition have been associated with vascular calcification, in addition to low bone mass. Usual dietary intakes of vitamin K are low. However, it is not known if these markers of vitamin K nutrition are indicators of generalized poor nutritional status in these studies. Furthermore, the impact of long-term vitamin K supplementation on vascular calcification has not been examined. In an ancillary study to a funded 3-year, double-blind, placebo controlled study on the effect of vitamin K supplementation on bone mineral density (BMD) and bone turnover, we propose to study the effect of vitamin K supplementation (500 g/d) on the progression of vascular calcification in 450 men and women, aged 60-80 years, who are already being monitored for bone loss. We will measure vascular calcification using electron beam computed tomography (EBCT) at the beginning and the end of 3 years of vitamin K supplementation. In addition, we will measure serum MGP and plasma lipids at 1, 6, 12, 24, and 36 months of vitamin K supplementation. Other covariates that will be collected through the course of the study as part of the funded study, include biochemical markers of vitamin K, vitamin D and calcium, markers of bone turnover, BMD of the hip, age, anthropometric data, physical activity, dietary intakes, medication use, and smoking. The proposed ancillary trial provides a unique opportunity to determine if vitamin K supplementation will reduce progression of vascular calcification in older men and women.
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