Vitamin D and respiratory tract infections in childhood

Abstract

BackgroundRespiratory tract infections (RTIs) remain among of the most important causes of morbidity and mortality among children. Several studies have associated vitamin D deficiency with an increased risk of RTIs, and vitamin D supplementation has been proposed as a possible preventive measure against RTIs in children. The main aim of this review is to summarize the current evidence from the literature about the link between vitamin D and RTIs in children.DiscussionSeveral recent studies have shown that vitamin D has different immunomodulatory properties associated with the risk of RTIs in childhood. In this regard, it is very important to understand the definition of deficiency and insufficiency of vitamin D and when and how to treat this condition. Unfortunately, there is no consensus, although a level of at least 10 ng/mL 25-hydroxycholecalciferol (25[OH]D) is thought to be necessary to promote bone mineralization and calcium homeostasis, and a concentration between 20 ng/mL and 50 ng/mL is considered adequate to provide an immunomodulatory effect. Available data support a role for vitamin D deficiency in the risk of pediatric tuberculosis, recurrent acute otitis media, and severe bronchiolitis, whereas further studies are needed to confirm an association in children with recurrent pharyngotonsillitis, acute rhinosinusitis and community-acquired pneumonia.ConclusionsMaintenance of adequate vitamin D status may be an effective and inexpensive prophylactic method against some RTIs, but the supplementation regimen has not been clearly defined. Further clinical trials are needed to determine the 25(OH)D concentrations associated with an increased risk of RTIs and optimal vitamin D supplementation regimen according to the type of RTI while also taking into consideration vitamin D receptor polymorphisms.

Immunomodulatory Effect of Vitamin D in Children with Allergic Diseases

“…In the past decade of twentieth century there was evidence that there is higher incidence of recurrent respiratory tract infection and nutritional rickets [48,49]. The evidence that the peak of viral infection is in the winter time when synthesis of vitamin D across the skin is naturally impaired supported that association.…”

“…The evidence that the peak of viral infection is in the winter time when synthesis of vitamin D across the skin is naturally impaired supported that association. In addition, other studies have proved that vitamin D deficiency in pregnant women may result in increased risk of respiratory tract infections in their infants [44][45][46][47][48][49]. The majority of immune cells express VDRs, mainly after they themselves have been stimulated [40,41,48].…”

“…The mechanism by which vitamin D regulates inflammation and immunity is complicated. It controls macrophage and dendritic cell activities and various Toll-like receptor mediated events in neutrophils [40,41], and it diminishes the function of human dendritic cells by decreasing maturation, antigen presentation, and the production of cytokines such as interleukin (IL)-12 and IL-23 [42,48].…”

“…Furthermore, treating macrophages with vitamin D result in the expression of various cytokines and chemokines, including CXCL8, IL-6, and IL-12, and tumor necrosis factor-α [48]. Additionally, vitamin D induces the expression of two antimicrobial peptides-cathelicidin and β-defensin-that are widely expressed in the body and play a key role in innate immunity owing to their chemotactic action and toxin neutralization [48].…”

“…Additionally, vitamin D induces the expression of two antimicrobial peptides-cathelicidin and β-defensin-that are widely expressed in the body and play a key role in innate immunity owing to their chemotactic action and toxin neutralization [48].…”