Functional effects of vitamin D: From nutrient to immunomodulator

Abstract

Vitamin D can be obtained from the endogenous synthesis in the epidermis by exposure to UVB light, and from foods and supplements in the form of ergocalciferol (vitamin D₂) and cholecalciferol (vitamin D₃). The main metabolite used to measure vitamin D serum status is calcidiol [25(OH)D]. However, its active metabolite calcitriol [1α,25(OH)₂D] performs pleiotropic effects in the cardiovascular, neurological, and adipose tissue as well as immune cells. Calcitriol exerts its effects through genomic mechanisms modulated by the nuclear vitamin D receptor (VDR)/retinoid X receptor (RXR) complex, to bind to vitamin D response elements (VDRE) in target genes of several cells such as activated T and B lymphocytes, neutrophils, macrophages, and dendritic cells; besides of its genomic mechanisms, VDR performs novel non-genomic mechanisms that involve its membrane expression and soluble form; highlighting that vitamin D could be an immunomodulatory nutrient that plays a key role during physiological and pathological events. Therefore, the aim of this comprehensive literature review was to describe the most relevant findings of vitamin D dietary sources, absorption, synthesis, metabolism, and factors that influence its serum status, signaling pathways, and biological effects of this immunonutrient in the health and disease.

Keywords:

• Calcidiol
• calcitriol
• absorption
• metabolism
• immunonutrient
• VDR

Disclosure statement

The authors declare that they have no conflict of interest or competing for financial interest.Figures were created with BioRender software, ©biorender.com.

Additional information

Funding

The authors acknowledge the support of the grant PRO-SNI 2017-2020 to Ulises de la Cruz-Mosso, from the Programa de Apoyo a la Mejora en las Condiciones de Producción de los Miembros del SNI y SNCA 2017-2020 of the University of Guadalajara. The funding sources were not involved in any step of this literature review.