Los Angeles (Xinhua): Chronic vitamin D deficiency may be a culprit in heart disease, high blood pressure and metabolic syndrome, a new study has suggested.

The lack of sunshine during winter may diminish vitamin D levels in the body and harm cardiovascular health, according to the study conducted by researchers at the Marcella Niehoff School of Nursing at Loyola University in Chicago.

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, said the study.

The researchers 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 is not sufficient to manage vitamin D levels, said the study.

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 mg/mL of vitamin D, the study suggested.

"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," said study author Sue Penckofer.

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