Effect of vitamin D 3 treatment on endothelial function in obese adolescents

Summary Background Obesity in children is associated with vitamin D deficiency and endothelial dysfunction. It is not known if treatment with vitamin D improves endothelial function in obese adolescents. Objective This study aimed to determine whether treatment with vitamin D 3 improves endothelial function in obese adolescents. Methods Nineteen obese adolescents, 13–18 years of age, with 25‐hydroxy vitamin D (25[ OH ] D ) levels <75 nmol L −1 were treated with 100 000  IU vitamin D 3 orally once a month for 3 months in an open‐label, single‐centre prospective trial. Endothelial function was assessed by flow‐mediated dilatation ( FMD ) of the brachial artery at study entry and 1 month after the third dose of vitamin D 3 . Biochemical parameters, including calcium, fasting lipids, glucose, insulin and high‐sensitivity C ‐reactive protein, were also obtained. Results Mean 25( OH ) D levels increased from 55.9 ± 12.2 to 86.9 ± 16.7 nmol L −1 ( P  < 0.01). There was no correlation between 25( OH ) D levels and brachial artery FMD . The brachial artery FMD (%) did not change significantly following vitamin D 3 treatment (9.5 ± 3.53 vs. 10.3 ± 3.83, P  = 0.83). Serum parathyroid hormone declined from 3.8 ± 1.5 to 3.1 ± 1 pmol L −1 ( P  = 0.01). The remainder of biochemical measurements did not show a significant change. Conclusions Treatment with vitamin D 3 , 100 000  IU once a month for 3 months was effective in increasing 25( OH ) D levels in obese adolescents but did not impact endothelial function.