Investigators at the Medical College of Georgia and Boston University Medical Center endeavored to assess 25(OH) D concentrations in response to 2,000 IU vitamin D supplementation over time; evaluate whether 2,000 IU achieves optimal vitamin D status; determine the relationship between adiposity and 25(OH)D concentrations; and measure the effect of vitamin D supplementation on arterial stiffness measured by pulse wave velocity (PWV).
Forty-nine African American adolescents (16.3 ± 1.4 years) were randomly assigned to either a control group (400 IU/day D3) or an experimental group (2,000 IU/day D3) over a 16-week period. Compliance (pill counts), calcium and vitamin D intake, and sun exposure were monitored. Body mass index (BMI), blood (25[OH] D and PTH), and urine (overnight urine calcium) were obtained at baseline, 4, 8, and 16 weeks. DEXA studies (Hologic QDR-4500W) were obtained at baseline and 16 weeks to measure body fat mass. Carotid-femoral, carotid-radial, and carotid-dorsalis pedis pulse wave velocity (PWV) measurements were obtained at baseline and 16 weeks. Vitamin D deficiency was classified as a 25(OH)D value less than 50 nmol/L, insufficiency as between 50–75 nmol/L 25(OH) D, and sufficiency as greater than 75 nmol/L 25(OH)D.
The average 25(OH)D level of all participants at baseline was 33.4 nmol/L, indicative of vitamin D deficiency. Plasma 25(OH)D levels were significantly higher in the 2,000 IU group at 8 and 16 weeks, with only 4.4% remaining vitamin D-deficient. Sixty-one percent of the control group remained vitamin D-deficient by the end of the study. PTH levels did not change significantly in either group.
Measures of total body fat mass did not correlate significantly with 25(OH)D levels in the control group whereas the experimental group consistently demonstrated an inverse correlation, achieving significance by week 4 (r = −0.63).
The control group demonstrated a significant increase in carotid-femoral PWV between baseline measures and week 16 while the experimental group had a significant reduction in carotid-femoral PWV between baseline and week 16.
Systolic and diastolic blood pressures remained unchanged over the course of the study and there were no differences noted in sun exposure, vitamin D intake, or physical activity from baseline to week 16 in both control and experimental groups.
The authors conclude that daily supplementation with 2,000 IU vitamin D may be effective in optimizing vitamin D status and counteracting the progression of aortic stiffness in black youth. Plasma 25(OH)D concentrations in response to the 2,000 IU/d supplementation are negatively modulated by adiposity.
Dr Heinze has disclosed no financial relationship relevant to this commentary. This commentary does not contain a discussion of an unapproved/investigative use of a commercial product/device
Vitamin D deficiency is described in numerous settings both in adults and in children.1 Recent reports...