Vitamin D has been tested in various clinical trials to prevent or reduce vascular calcification and cardiac complications in patients, particularly patients with CKD, based on data from rodent models showing beneficial effects on the heart and vasculature, the association of low vitamin D levels and CVD in epidemiological studies, and the ability of calcitriol to reduce the activity of the RAAS and to suppress PTH secretion [293]. This evidence concerns the gene PTH and chronic kidney disease.