Vinet A, Morrissey C, Perez-Martin A, et al. - Given the evidence that vitamin D (VD) may improve vascular function, researchers, for the first time, conducted this randomized controlled trial to examine the impact of VD supplementation on microvascular reactivity in obese adolescents (OA). The sample consisted of 26 OA, receiving fruit juice with (n = 13) or without VD (4,000 IU/d; n = 13) over a 3-month lifestyle program, as well as 23 normal-weight adolescents (controls). Changes in 25 hydroxyvitamin D (25(OH)D), flow-mediated dilation, nitrate-mediated dilation, insulin resistance (HOMA-IR) and inflammatory markers (C-reactive protein) have been monitored. VD supplementation during a lifestyle program reduced microvascular dysfunction in OA while having no effect on macrovascular function.