November 20 (HealthDay News) -- The lack of sunshine during winter may diminish vitamin D levels in the body and harm cardiovascular health, U.S. researchers say.

The body needs sunshine to produce vitamin D, but that process is slowed in the winter due to less daylight and spending more time indoors.

"Chronic vitamin D deficiency may be a culprit in heart disease, high blood pressure and metabolic syndrome," study author Sue Penckofer, a professor at the Marcella Niehoff School of Nursing at Loyola University in Chicago, said in a university news release.

She and her colleagues reviewed a number of studies that linked vitamin D deficiency to heart disease. The studies said rates of severe heart disease or death may be 30 percent to 50 percent higher in sun-deprived heart disease patients.

Diet alone isn't sufficient to manage vitamin D levels, Penckofer and her team concluded. Treatment options, such as vitamin D2 or D3, may decrease the risk of severe heart disease or death. The preferred range in the body is 30-60 ng/mL of 25 (OH) vitamin D.

"Most physicians do not routinely test for vitamin D deficiency. However, most experts would agree that adults at risk for heart disease and others who experience fatigue, joint pain, or depression should have their vitamin D levels measured," Penckofer said.

The study was published in the current issue of the journal Circulation.

SOURCE: Loyola University Medical Center, news release, November 2008