INS and diabetes mellitus: [7], [8]. At high doses calcitriol prevents insulitis and the development of experimental diabetes, by acting on the defective suppressor cellular function, or cytokine expression modulation [7], [9]. Moreover, supplementation with vitamin D during early childhood may decrease the risk of developing T1D [10], [11]. Contrary to what was expected, we have found that calcitriol supplementation is not effective in improving β-cell function or reducing insulin requirement in patients with newly diagnosed T1D [12].