"While we think of the sun as providing humans with most of our body's requirement of vitamin D, 95 percent of the 44 black teenagers living in sunny Georgia who took part in this study were classified as vitamin D deficient," said Yanbin Dong, MD, PhD, of the Medical College of Georgia in Augusta and lead author of the study. "Our study shows that vitamin D supplementation may improve cardiovascular health in black teens who don't get enough vitamin D from their diet and sun exposure."

In this study, 44 black teenagers (male and female) were randomly assigned to receive either 400 IU of vitamin D per day as recommended by the American Academy of Pediatrics or 2,000 IU of vitamin D per day. Study subjects taking 400 IU of vitamin D per day did not achieve vitamin D sufficiency, while their peers who took 2,000 IU of vitamin D per day on average became vitamin D sufficient.

Researchers measured arterial stiffness in study subjects using pulse wave velocity (PWV), a non-invasive procedure where a pulse is emitted at two arterial sites. The pulse's transit time and distance travelled help researchers reliably calculate arterial stiffness. Results from the study showed that vitamin D may protect vascular systems and that sufficient supplementation of vitamin D could elicit favorable alterations in the arterial system and in cardiovascular function in general.

"Our study is the first clinical trial of vitamin D intervention to use 2,000 IU in black subjects and to include cardiovascular risk factors as outcomes in youth," said Dong. "Our study indicates that the current recommendations for vitamin D intake in black teenagers may need to be revised upward."

Other researchers working on the study include: Inger Stallmann-Jorgensen, Norman Pollock, Ryan Harris, Daniel Keeton, Ying Huang, Ke Li, Reda Bassali, Dehuang Guo, Jeffrey Thomas, Gary Pierce, Jennifer White and Haidong Zhu of the Medical College of Georgia in Augusta; and Michael Holick of Boston University Medical Center in Mass.

The article, "A 16-week randomized clinical trial of 2,000 IU daily vitamin D3 supplementation in black youth: 25-hydroxyvitamin D, adiposity, and arterial stiffness," will appear in the October 2010 issue of JCEM.

Note: If no author is given, the source is cited instead.

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