Vitamin D Prevents Heart
and Stroke-Related 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 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
D to many serious illnesses including diabetes, hypertension,
kidney and heart disease.
Lead author Kevin Fiscella, M.D., 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
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, a national expert on disparities in health care
and a professor of Family Medicine and Community and Preventive
Medicine at URMC.
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 U.S., inadequate Vitamin D has been reported
in about 36 percent of otherwise healthy young adults and about
57 percent of general medicine hospitalized patients.
Vitamin D is metabolized in the liver and converted to 25 hydroxyvitamin
D or 25(OH) D, the form used to determine a person's status through
a blood test. Deficiency is usually defined by levels of less
than 20 nanograms per milliliter; 30 ng/ml is viewed as sufficient.
The mean blood level in the study sample was 29.5 ng/ml.
Most of the body's tissues and cells have vitamin D receptors,
making it a potent regulator of cell activity and growth. A deficiency
contributes to inflammation associated with heart disease, many
cancers and poor bone health.
Fiscella cautions, however, 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, (particularly
housebound or nursing home residents), 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.
January 7, 2010