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January 18, 2010

Study links vitamin D, race, and cardiac deaths

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

The journal Annals of Family Medicine is publishing the study in the January-February edition. 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 D to many serious illnesses, including diabetes, hypertension, kidney, and heart disease.

Lead author Kevin Fiscella, a professor of family medicine and community and preventive medicine, says 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.

yellow pills
Genetic factors common to blacks
sometimes preclude vitamin D
absorption.

"Therefore, our study suggests that
the next step would be to intervene
to boost vitamin D levels safely, with
supplements,” said Kevin Fiscella, a
professor of family medicine and
community and preventive medicine.

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 Fiscella.

With funding through the National Heart Lung and Blood Institute, 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 percent higher risk of death from cardiac illness. This suggests that vitamin D may be a modifiable, independent risk factor for heart disease, Fiscella said.

Most striking, however, was that when researchers adjusted the statistics to look at race, blacks had a 38 percent 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.

A review article published in September 2009 in The American Journal of Medicine, noted that Vitamin D deficiency is a worldwide  health problem. In the United States, inadequate vitamin D has been reported in about 36 percent of otherwise healthy young adults   and about 57 percent of general medicine hospitalized patients.

Fiscella cautions that not all observational studies of vitamin deficiency are borne out by subsequent clinical trials. For example, previous observational studies of vitamin E and beta-carotene that  were associated with poor heart health did not hold up in later clinical studies. The need to further assess the vitamin D connection to heart disease is convincing, however, particularly among blacks, he added.

Other at-risk people include the obese and the elderly because vitamin D levels decline with age. And although more sun exposure can boost levels of D, skin cancer is also an increasing risk to many people. Therefore, medical authorities usually recommend increased dietary intake and/or supplementation as the best way to correct a deficiency.

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