Tangpricha and colleagues, all from Emory University School of Medicine in Atlanta, looked at the association between systolic blood pressure - the top number of the blood pressure reading representing the pressure during contraction of the heart muscle -- and vitamin D levels among 7,699 adults without high blood pressure. Forty-seven percent were male, 61 percent were white, and 39 percent were black.

The study population had participated in the third National Health and Examination Survey conducted from 1988 to 1994, which provides the most recent nationally representative data on vitamin D concentrations among U.S. adults, the investigators report in the American Journal of Clinical Nutrition.

Overall, 61 percent of whites and 92 percent of blacks had vitamin D deficiency. Most (63 percent) of the participants were 18 to 49 years old, and 37 percent were 50 years or older when systolic blood pressure and vitamin D measurements were obtained.

The investigators found that white participants with sufficient vitamin D levels had a 20-percent lower rise in age-associated systolic blood pressure compared with those with insufficient vitamin D levels. This relationship was not statistically significant in blacks.

"This paper does not provide direct evidence that vitamin D supplementation will lower blood pressure," Tangpricha cautions.

He and colleagues suggest that further research examine in more detail how vitamin D status affects blood pressure in black and white populations. Improved methods for detecting vitamin D deficiency are also necessary, they conclude.

SOURCE: American Journal of Clinical Nutrition, January 2008.

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