Asian Brown could feel the difference when he started taking vitamin D supplements, and the 16-year-old student of A.R. Johnson Health Science and Engineering Magnet School might be just the beginning.

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Asian Brown (right) was among the teens who participated in Dr. Yanbin Dong's research.

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Asian was part of a study at the Georgia Prevention Institute at Medical College of Georgia that was the first to look at vitamin D supplementation in black teens and its impact on the cardiovascular system.

Dr. Yanbin Dong found that those taking the highest supplement dose of 2,000 international units per day had a significant decrease in pulse wave velocity, a measure of arterial stiffness that can lead later on to cardiovascular problems.

Vitamin D can be converted from sunlight exposure or come from certain foods like oily fish or milk, said Dong, a cardiologist and geneticist at the institute. It had long been assumed that people living in sunnier climates like the South would have adequate levels, but an earlier study at the institute of 600 children found the opposite was true, he said.

"Startlingly we found, regardless of your race, vitamin D insufficiency was very common in kids living in Augusta and the surrounding area, and particularly worse in African-American kids," Dong said.

It is lower in blacks because darker skin might make it harder to convert sunlight and because of differences in diet, he said.

"A lot of African-American kids didn't have access to grocery stores," and also drank less milk, he said. Health problems such as cardiovascular disease and diabetes are also disproportionately higher in blacks, and this study found a correlation between lower vitamin D levels and higher blood pressure, among other things.

The journal study followed 44 black teens for 16 weeks, with about half taking 400 IU per day, the amount recommended by the American Academy of Pediatrics, and the other half the 2,000-a-day dose that Dong believes is probably better. That highest dose group was the one that showed "statistically significant" drops in the pulse wave velocity and arterial stiffness, he said. Unfortunately, blood levels of vitamin D were lower in those with higher body weights because the vitamin D got absorbed more into the fat.

It is not clear why vitamin D appears to have this effect, but it is likely due to an ability to lower inflammation and reduce oxidative stress, among other things, Dong said. A review article published online last month in Current Opinion in Cardiology noted "substantial clinical evidence" of vitamin D deficiency worsening cardiovascular health but called for more studies before recommending routine supplementation as a preventative measure for heart disease. The results of the MCG study will be published in the October issue of the Journal of Clinical Endocrinology & Metabolism .

Dong will next study vitamin D supplementation in black adults and would like to do another study in children but follow them for a year.

"Our next step would be to see the sustainability," he said.

Dong cautioned that the vitamin supplement is not "a magic pill. If you have hypertension, vitamin D alone cannot cure it. But it may help you. How much vitamin D will be beneficial , we don't know. There's a lot of questions."