A most interesting piece of research on the relationship of heart disease to blood levels of vitamin D was recently published in the American Journal of Cardiology. Researchers from the Intermountain Heart Collaborative (IHC) Study Group studied 41,497 subjects with at least one vitamin D measurement from 2000-2009. The prevalence of vitamin D deficiency in the subjects was 63.6%. The researchers found that during that time period, those with the lowest levels of vitamin D had highly significantly increased risk of developing diabetes, hypertension (high blood pressure), hyperlipidemia (high cholesterol and triglycerides) and peripheral vascular disease, all diseases in their own right, and all risk factors for developing heart disease. They also found that those who had none of these risk factors, but who had severe D deficiency, had an increased risk of developing diabetes, hypertension and hyperlipidemia.
Low vitamin D levels were also correlated closely to coronary artery disease, myocardial infarction (heart attack), heart failure, stroke and overall risk of death (not surprising). Of particular interest was the fact that hypertension was nearly 90% more likely in those with low vitamin D levels (less than 15 ng/ml) compared to those who had high levels (greater than 30 ng/ml). Unfortunately, the analysis did not compare those who were severely deficient with those who had "optimal levels," which I would consider to be 60 ng/ml or more. Had they done that, it is likely that the differences in disease and death rates would have been even more impressive. Other findings of this study showed that infections, kidney failure and fractures were more likely among those with the lowest levels of vitamin D.
This research is one of the best conducted and controlled that I've seen, but it is hardly the only finding that showed a dramatic increase in these diseases when comparing people with low vitamin D levels to those with higher levels. One of the most impressive compared the risk of heart attack with vitamin D levels and found those with the lowest D levels to have 2.4 times the risk of heart attack compared to those with the higher levels.
As you can see, vitamin D makes a difference. if you'd rather not have a heart attack, it behooves you to optimize your vitamin D levels!
There are another dozen research papers that point out a terrific difference in heart disease rates among people with different vitamin D blood levels; however, they all come to the same conclusion. Get some sunlight and optimize your vitamin D levels!
 Jeffrey L. Anderson, MD, Heidi T. May, PhD, MSPH Benjamin D. Horne, PhD, MPH
Tami L. Bair, BS Nathaniel L. Hall, MD,, John F. Carlquist, PhD, Donald L. Lappé, MD, and
Joseph B. Muhlestein, MD Relation of Vitamin D Deficiency to Cardiovascular Risk Factors,
Disease Status, and Incident Events in a General Healthcare Population. Am J Cardiol 2010;106:963–968)
 Giovannucci E, Liu Y, Hollis BW, Rimm EB. 25-Hydroxyvitamin D and risk of myocardial infarction in men. Arch Intern Med 2008;168:1174–1180.