Vitamin D3 Supplementation for 16 Weeks Improves Flow-Mediated Dilation in Overweight African-American Adults

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 D3 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 D3 (n=22; mean age 29±2 years), serum concentrations of 25 hydroxyvitamin D increased from 38.2±3.0 nmol/L to 48.7±3.2 nmol/L and 34.3±2.2 nmol/L to 100.9±6.6 nmol/L, respectively. No changes in serum parathyroid hormone, 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, AUC × 103) following treatment, whereas no change (-0.005±0.002 cm and -0.02±0.02 %/s-1, AUC, respectively) was observed following placebo. Conclusions Supplementation of 60,000 IU monthly oral vitamin D3 (~2000 IU per day) for 16 weeks is effective at improving vascular endothelial function in African American adults.

Oral supplementation with 25(OH)D3 versus vitamin D3: Effects on 25(OH)D levels, lower extremity function, blood pressure, and markers of innate immunity

“…(31) Second, vitamin D 3 supplementation ($2000 IU/d) was found to improve endothelial function in a trial among African American individuals compared to placebo. (32) Third, mice lacking the vitamin D receptor (VDR) suffer from hypertension and develop heart hypertrophy. (33,34) Fourth, clinically, in two small trials among patients with mild hypertension and older postmenopausal women, ultraviolet B (UVB) irradiation or vitamin D supplementation (800 IU/d) reduced blood pressure by 6 to 9 mmHg.…”

Vitamin D and risk of CVD: a review of the evidence

“…A couple of cross-sectional studies in healthy adults show lower serum levels of 25(OH)D to be associated with endothelial dysfunction (91,92) . A few trials show an improvement in flow-mediated dilation with vitamin D supplementation (93)(94)(95) , but most show no effect (79,(96)(97)(98) ( Table 2).…”

High Prevalence of Hypovitaminosis D in Postmenopausal Women with Type 2 Diabetes Mellitus

“…We have found no association between 25-OH D, PTH or body mass indices with fasting glycemia, HbA1c or duration of diabetes. Although epidemiological studies and meta-analysis showed an association between low serum 25-OH D and impaired glycaemia (Pittas et al, 2010;Mitri et al, 2011), vitamin D intervention trials have had inconsistent results (Avenell et al, 2009;Von Hurst et al, 2010;Harris et al, 2011;Davidson et al, 2013). Therefore, it is uncertain whether vitamin D deficiency and poor glycemic control are causally interrelated or they represent two independent features of T2DM.…”