(CBS) Call it a bit of sunshine for African-Americans at high risk for heart disease. A new study shows that supplements of vitamin D - sometimes called the "sunshine vitamin" because the body produces it upon exposure to sunlight - curbs African-Americans' cardiovascular risk by improving the health of blood vessels.
The finding could be significant, because blacks often face a higher risk for cardiovascular disease than other groups.
Blacks are more likely to develop type 2 diabetes and severe high blood pressure - both of which are risk factors for cardiovascular disease, according to a statement released in conjunction with the study. And because dark pigmentation inhibits skin cells' ability to make vitamin D in response to ultraviolet light, blacks are more likely to be deficient in vitamin D.
Vitamin D deficiency is another major cardiovascular risk factor.
In the study, conducted by researchers at Georgia Health Sciences University in Augusta, 45 overweight African-American adults were separated into two groups. One group got 60,000 international units (IU) of vitamin D in a single dose every four weeks for 16 weeks (roughly equivalent to getting 2,000 IU a day). The other group got a placebo.
Before and after the study period, researchers used ultrasound to gauge the ability of blood vessels to dilate. Poor dilation is considered evidence of "hardening of the arteries," or atherosclerosis, which can cause heart attack and stroke. At the end of the study, blood vessel dilation had improved in the vitamin D group but not in the placebo group.
"This points to a beneficial effect of vitamin D supplementation on endothelial cell function," researcher Dr. Ryan A. Harris, an assistant professor at the university, said in the statement. "If you're deficient in vitamin D and you take supplements, you have a good probability of increasing endothelial function and therefore decreasing the risk of cardiovascular disease."
Exactly how vitamin D works its magic is the "million-dollar question," Harris said, adding that more research was needed to gauge the vitamin's long-term benefits. "Vitamin D interacts with a lot of different systems in the body," he said. "It may decrease inflammation, which is better for endothelial function."