Analyzing data on more than 10,000 patients, University of Kansas researchers found that 70 percent were deficient in vitamin D and they were at significantly higher risk for a variety of heart diseases.
D-deficiency also nearly doubled a person's likelihood of dying, whereas correcting the deficiency with supplements lowered their risk of death by 60 percent.
"We expected to see that there was a relationship between heart disease and vitamin D deficiency; we were surprised at how strong it was," assured Dr. James L. Vacek, a professor of cardiology at the University of Kansas Hospital and Medical Center .
"It was so much more profound than we expected."
Vitamin D deficiency has been linked to a range of illnesses, but few studies have demonstrated the reverse -- that supplements could prevent those outcomes.
Vacek and his team reviewed data from 10,899 adults whose vitamin D serum levels had been tested at the University of Kansas Hospital, and found that more than 70 percent of the patients were below 30 nanograms per milliliter, the level many experts consider sufficient for good health.
After taking into account the patients' medical history, medications and other factors, the cardiologists found that people with deficient levels of vitamin D were more than twice as likely to have diabetes, 40 percent more likely to have high blood pressure and about 30 percent more likely to suffer from cardiomyopathy -- a diseased heart muscle -- as people without D deficiency.
Overall, those who were deficient in D had a three-fold higher likelihood of dying from any cause than those who weren't deficient, the researchers reported in the American Journal of Cardiology. Moreover, when the team looked at people who took vitamin D supplements, their risk of death from any cause was about 60 percent lower than the rest of the patients, although the effect was strongest among those who were vitamin D deficient at the time they were tested.