Vitamin D (VD) is an essential hormone for humans. Despite the classical functions of VD in the regulation of calcium-phosphorus homeostasis and bone metabolism, in the last few years, evidence has been accumulated on the pleiotropic effect of VD, as many cells throughout the body express the VD receptor and the enzyme 1α-hydroxylase. 1 This article discusses the actions of VD and the relationship between VD status and the risk to develop various diseases.
| VITAMIN D ME TABOLIS MVitamin D is the general term encompassing both vitamin D 2 (ergocalciferol) and vitamin D 3 (cholecalciferol). In humans, VD is mainly synthesized in the skin, whereas only a minor part is derived from dietary sources. Few natural, non-fortified products such as fatty fish or some types of mushrooms contain relevant amounts of VD. The endogenous synthesis pathway starts in the skin, when cutaneous-derived 7-dehydroxycholesterol undergoes photolytic conversion by UVB sunlight to form pre-vitamin D3, rapidly converted to biologically inactive vitamin D3. It then undergoes hydroxylation in the liver by 25-hydroxylase to become 25-(OH) D, the major circulating form of VD in humans. In the kidney, 25(OH) D is further converted to the fully active metabolite 1,25-(OH)2 D by the enzyme 1-α-hydroxylase. This process is finely regulated by parathormone, fibroblast growth factor 23, calcium, and phosphorus and depends on some factors such as ethnicity, latitude, culture, and sunscreen. 2 VD plays a fundamental role in the processes of acquisition and achievement of peak bone mass. 3,4
| E X TR A S K ELE TAL AC TI ON S OF VDIn recent decades, several studies have suggested that VD contributes to diverse processes extending far beyond mineral homeostasis, defined as extraskeletal actions. These observations suggest a critical role for VD in the modulation of immune function, above all during pediatric age, exerted by modulating both innate immunity
AbstractSeveral scientific societies established that vitamin D (VD), in its metabolized form 25(OH)D, levels higher than 20 ng/mL are sufficient to ensure optimal bone health, while 25(OH)D levels higher than 30 ng/mL are needed to favor VD extraskeletal actions. However, it has been estimated that approximately 30% of children and 60% of adults worldwide are VD deficient and insufficient, respectively. This is the reason why it is important to provide a practical approach to VD supplementation for infants, children, and adolescents. It is the pediatrician's role to evaluate the modifiable lifestyle risk factors for deficiency, particularly a reduced sun exposure, following an evidence-based approach, and to suggest VD supplementation only when there is a rational reason to support its use. K E Y W O R D S childhood disorders, health, vitamin D3 How to cite this article: Peroni DG, Trambusti I, Di Cicco ME, Nuzzi G. Vitamin D in pediatric health and disease. Pediatr Allergy Immunol. 2020;31(Suppl 24):54-57. https ://doi.