Vitamin D deficiency may contribute to a higher number of heart and stroke-related deaths among black Americans compared to whites, according to a University of Rochester Medical Center study.

The journal Annals of Family Medicine is publishing the study in the January-February edition, which goes online Jan. 11, 2010.

Researchers sought to understand the well-documented disparity between blacks and whites in cardiovascular deaths. They turned to vitamin D because growing evidence links low serum levels of vitamin D to many serious illnesses including diabetes, hypertension, kidney and heart disease.

Lead author Kevin Fiscella, MD, said a complex host of genetic and lifestyle factors among blacks may explain why this population group has lower vitamin D levels across the lifespan than other races.

People get vitamin D through their diets, sun exposure and oral supplements. Genetic factors common to blacks sometimes preclude vitamin D absorption, such as a higher incidence of lactose intolerance, which can eliminate vitamin D fortified milk from the diet, and darker skin pigment that significantly reduces vitamin D synthesis.

“Therefore, our study suggests that the next step would be to intervene to boost vitamin D levels safely, with supplements,” said Dr. Fiscella, a national expert on disparities in healthcare and a professor of Family Medicine and Community and Preventive Medicine at URMC.

With funding through The National Heart Lung and Blood Institute, Dr. Fiscella and colleagues studied a sample of more than 15,000 American adults. The data included measurements of blood levels of vitamin D and death rates due to cardiovascular disease. Researchers also looked at other factors that contribute to heart health, such as body mass index, smoking status and levels of C-reactive protein.

Overall, the analysis showed that, as expected, a vitamin D deficiency was associated with higher rates of death among all people in the sample. In fact, those adults with the worst deficiency had a 40% higher risk of death from cardiac illness. This suggests that vitamin D may be a modifiable, independent risk factor for heart disease, Dr. Fiscella said.

Most striking, however, was that when researchers adjusted the statistics to look at race, blacks had a 38% higher risk of death than whites. As vitamin D levels rose, however, the risk of death was reduced. The same was true when researchers analyzed the effect of poverty on cardiovascular death rates among blacks, which suggests that vitamin D deficiency and poverty each exert separate risk factors, the study said.