SUNDAY, Nov. 14 (HealthDay News) -- New research suggests that vitamin D deficiency does not boost stroke death rates among black patients, even though it appears to double the risk for whites.

The authors expressed some surprise at the findings, given that prior research has revealed that blacks are overall more prone to vitamin D deficiency and more likely to experience a stroke, compared with white patients. Blacks also have a 60 percent higher risk of dying from a stroke than whites, they added.

"We thought maybe the lower vitamin D levels might actually explain why blacks have higher risks for stroke," study author Dr. Erin Michos, an assistant professor of medicine at Johns Hopkins University School of Medicine in Baltimore, said in a news release from the American Heart Association. "But we did not find the same relationship between vitamin D and stroke in blacks."

Michos and his colleagues are slated to present their findings Monday at the American Heart Association annual meeting in Chicago.

Stroke is the third most common cause of death in the United States, the authors noted.

Their analysis stems from a review of health records of approximately 8,000 adults obtained from the Third National Health and Nutrition Examination Survey of Americans (NHANES-III) conducted between 1988 and 1994.

Almost 7 percent of the white patients were vitamin D-deficient, compared with more than 32 percent of the black participants. Whites with too little Vitamin D had twice the risk of dying from stroke as whites with adequate levels of the vitamin, which is obtained from fortified dairy products, fatty fish and exposure to sunlight.

The findings held up even after accounting for a host of socioeconomic and stroke risk factors, such as a history of diabetes, high blood pressure, cholesterol, body-mass index, smoking, physical activity and/or alcohol use.

Blacks could have a natural resistance to the negative effects of vitamin D deficiency, Michos said. This could explain why blacks have fewer bone fractures than whites, despite the higher incidence of low vitamin D levels, Michos added.

More information

For more on vitamin D, visit the U.S. National Institutes of Health.