Researchers looked at the blood samples of more than 10,000 people in Denmark and found that those with low levels of vitamin D were 64% more likely to suffer a heart attack and 57% more likely to die prematurely than those with the highest levels. They also had a 40% greater risk of ischemic heart disease and at least an 81% higher risk of heart disease-related death. The study appeared in the journal Arteriosclerosis, Thrombosis and Vascular Biology.