Substantial evidence suggests that a large portion of the population have suboptimal levels of vitamin D, which may adversely affect the cardiovascular (CV) system, including increasing levels of parathyroid hormone, activating the renin-angiotensin-aldosterone system, and increasing insulin resistance, thus leading to hypertension and left ventricular hypertrophy, metabolic syndrome/diabetes mellitus, systemic inflammation, and increased risk of atherosclerosis and CV disease events. We review the evidence that vitamin D deficiency is associated with incident CV disease events, as well as evidence that vitamin D supplementation is associated with reduction in CV diseases. Although the current evidence has created substantial hype, randomized controlled trials are needed to determine whether routine vitamin D assessment and supplementation will improve CV outcomes. (J Am Coll Cardiol 2011;58:1547-56) (C) 2011 by the American College of Cardiology Foundation
