Vitamin K intake and mortality in people with chronic kidney disease from NHANES III

Background & aims: Cardiovascular disease (CVD) is the leading cause of death in patients with chronic kidney disease (CKD), partly due to increased vascular calcification. Vitamin K plays a role in preventing vascular calcification in CKD yet the relationship between vitamin K intake and mortality in CKD patients remains unclear. Methods: This observational cohort study included 3401 participants with CKD from the Third National Health and Nutrition Examination Survey. Vitamin K intake was estimated from 24-h dietary recalls (1988-94). Mortality was determined from the National Death Index records through 2006. Cox-proportional hazards regression was used to estimate Hazard Ratios (HR) by comparing those with adequate intake of vitamin K to those with low intake, adjusting for advanced CKD covariates. For sensitivity analysis, these associations were also examined among those with different renal status. Results: During a median follow-up of 13.3 years (37,408 person-years), 1815 and 876 participants died from all-cause and CVD causes, respectively. 72% of the participants had vitamin K intake lower than the recommended adequate intake. Participants with vitamin K intake higher than recommended adequate intake for vitamin K were associated with lower risk of all-cause (HR = 0.85; 95%: 0.72-1; P = 0.047) and CVD mortality (HR = 0.78; 95%: 0.64-95; P = 0.016). Sensitivity analyses in subgroups with advanced CKD revealed similar findings. Conclusions: This observational study suggests that adequate intake of vitamin K may be associated with reduced all-cause and CVD mortality in CKD patients. However, vitamin K may be a marker of a healthy diet; therefore clinical trials may help in clarifying the effect of vitamin K independent of a healthy diet. (C) 2014 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.