In people with low blood levels of vitamin D, boosting them with supplements more than halved a person's risk of dying from any cause compared to someone who remained deficient, in a large new study.

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," says Dr James L. Vacek, a professor of cardiology at the University of Kansas Hospital and Medical Center.

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.