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Vitamin D3 supplementation for 16 weeks improves flow-mediated dilation in overweight African-American adults - PubMed

Randomized Controlled Trial

Vitamin D3 supplementation for 16 weeks improves flow-mediated dilation in overweight African-American adults

Ryan A Harris et al. Am J Hypertens. 2011 May.

Abstract

Background: A growing body of evidence has linked vitamin D deficiency to increased risk of cardiovascular disease. Vitamin D deficiency is also more common in African Americans for whom an increased cardiovascular disease risk exists. This study sought to test the hypothesis that 16 weeks of 60,000 IU monthly supplementation of oral vitamin D(3) would improve flow-mediated dilation (FMD) in African Americans, whereas no change would be observed in the placebo group.

Methods: A randomized, double-blind, placebo-controlled clinical trial was conducted. Fifty-seven African-American adults were randomly assigned to either the placebo group or vitamin D group.

Results: Following 16 weeks of placebo (n = 23; mean age 31 ± 2 years) or 60,000 IU monthly oral vitamin D(3) (n = 22; mean age 29 ± 2 years), serum concentrations of 25-hydroxyvitamin D (25(OH)D) increased from 38.2 ± 3.0 to 48.7 ± 3.2 nmol/l and 34.3 ± 2.2 to 100.9 ± 6.6 nmol/l, respectively. No changes in serum parathyroid hormone (PTH), serum calcium, or urine calcium/creatinine were observed following either treatment. Following 16 weeks of treatment, significant improvements in FMD were only observed in the vitamin D group (1.8 ± 1.3%), whereas the placebo group had no change (-1.3 ± 0.6%). Similarly, the vitamin D group exhibited an increase in absolute change in diameter (0.005 ± 0.004 cm) and FMD/shear (0.08 ± 0.04 %/s(-1), area under the curve (AUC) × 10(3)) following treatment, whereas no change (-0.005 ± 0.002 cm and -0.02 ± 0.02 %/s(-1), AUC, respectively) was observed following placebo.

Conclusion: Supplementation of 60,000 IU monthly oral vitamin D(3) (~2,000 IU/day) for 16 weeks is effective at improving vascular endothelial function in African-American adults.

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Figures

Figure 1
Figure 1

The effect of 16 weeks of placebo or vitamin D supplementation on 25 hydroxyvitamin D (25(OH)D), serum parathyroid hormone (PTH), and urinary calcium (Ca) / Creatinine (Cr) ratio. Data are presented as percent change from baseline. *Significant change from baseline. †Significant change from placebo.

Figure 2
Figure 2

The effect of 16 weeks of placebo or vitamin D treatment on A) flow-mediated dilation, B) shear rate area under the curve (AUC), and C) flow-mediated dilation normalized for shear rate. *Significant from vitamin D at baseline. †Significant from placebo at 16 weeks.

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