Vitamin D and Vascular Health in Children

Our primary objective is to determine, in obese and overweight children aged 10 to 18 years
with vitamin D deficiency (defined as serum 25-hydroxyvitamin D <20 ng/mL), the efficacy of
enhanced vitamin D3 supplementation in improving vascular endothelial function, arterial
stiffness, insulin sensitivity, and metabolic syndrome risk status; and to assess whether
these effects are dose-dependent. As a secondary objective, we will examine the vitamin D
supplementation-induced effect on adipokines and inflammatory markers relevant to CVD risk.
In a double-masked, controlled trial, we will randomize 252 eligible children to receive
either 600 IU (conventional supplementation), or 1000 IU or 2000 IU (enhanced
supplementation) of vitamin D3 daily for 6 months.

Inclusion Criteria:

- Eligible subjects will be 10 to 18 years of age;

- obese or overweight (BMI ≥85th %tile);

- otherwise healthy, and

- have a serum 25(OH)D concentration <20 ng/mL

Children taking multivitamins should be able to hold off their multivitamins during the
course of the study.

Exclusion Criteria:

Children will be excluded if they

- (a) have hepatic or renal disease, metabolic rickets, malabsorptive disorders, primary
hyperparathyroidism, hyperthyroidism, or other chronic disorders that could affect
vitamin D metabolism;

- (b) are receiving treatment with anticonvulsants, systemic glucocorticoids,
pharmacologic doses of vitamin D (≥1000 IU of vitamin D2 or D3 daily),
antihypertensives, vasoactive drugs, antilipidemics, metformin, antipsychotics, or
other oral insulin regulators;

- (c) have cholelithiasis or urolithiasis;

- (d) have type 1 or type 2 diabetes; or

- (e) have a condition or underlying abnormality that could compromise the safety of the
subject.

Post-menarchial girls with a positive pregnancy test at randomization, or subjects found
during the screening phase to have hypercalcemia (serum calcium >10.8 mg/dL) or significant
fasting hyperglycemia (fasting blood glucose ≥ 125 mg/dL) will also be excluded.