You can get vitamin D by drinking milk and eating foods fortified with the vitamin. But the body also makes vitamin D when exposed to sunlight. Studies have shown spikes in heart disease-related deaths at higher latitudes and during the winter months - areas and times of less daylight -- and decreases in such deaths at lower latitudes and during the summer.
For the current study, Edward Giovannucci, MD, ScD, of Harvard School of Public Health and Brigham and Women's Hospital, Boston, and colleagues reviewed medical records and blood samples of 454 men aged 40 to 75 who had heart attacks and survived or who had died of heart disease. They compared the information with similar data from 900 living men who did not have a history of heart disease, also noting the men's diet and lifestyle factors.
The researchers learned that men who had vitamin D levels of 15 ng/mL or less in their blood samples -- an indication of vitamin D deficiency -- had an increased risk for heart attack compared to those whose vitamin D level was considered sufficient (30 ng/mL). The twofold increased risk remained significant even when adjusting for other factors known to contribute to heart disease, such as high cholesterol, diabetes, high blood pressure, or a family history of heart disease.
Men with intermediate levels of vitamin D also were more likely to have a heart attack than those with adequate vitamin D levels.
"Vitamin D deficiency has been related to an increasing number of conditions and to total [death]. These results further support an important role for vitamin D in [heart attack] risk," the researchers say in a news release. "The present findings add further support that the current dietary requirements of vitamin D need to be increased to have an effect on [vitamin D] levels substantially large enough for potential health benefits."