How important is vitamin D in preventing infections?

Abstract

Interaction with the immune system is one of the most recently established nonclassic effects of vitamin D (VitD). For many years, this was considered to be limited to granulomatous diseases in which synthesis of active 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) or calcitriol is known to be increased. However, recent reports have supported a role for 1,25(OH)2D3 in promoting normal function of the innate and adaptive immune systems. Crucially, these effects seem to be mediated not only by the endocrine function of circulating calcitriol but also via paracrine (i.e., refers to effects to adjacent or nearby cells) and/or intracrine activity (i.e., refers to a hormone acting inside a cell) of 1,25(OH)2D3 from its precursor 25(OH)D3, the main circulating metabolite of VitD. The ability of this vitamin to influence human immune responsiveness seems to be highly dependent on the 25(OH)D3 status of individuals and may lead to aberrant response to infection or even to autoimmunity in those who are lacking VitD. The potential health significance of this has been underlined by increasing awareness of impaired status in populations across the globe. This review will examine the current understanding of how VitD status may modulate the responsiveness of the human immune system. Furthermore, we discuss how it may play a role in host resistance to common pathogens and how effective is its supplementation for treatment or prevention of infectious diseases in humans.

Invasive infections due to Streptococcus pyogenes: seasonal variation of severity and clinical characteristics, Iceland, 1975 to 2012

“…Seasonal variation in vitamin D levels has been proposed to affect immune function [34]. Indeed, previous work from Iceland has shown that vitamin D levels are lowest in February to March and highest in June to July [35].…”

Supplementation of Merino ewes with cholecalciferol in late pregnancy improves the vitamin D status of ewes and lambs at birth but is not correlated with an improvement in immune function in lambs

“…Vitamin D has been recognised to have several roles in the regulation of immune function and can enhance innate antimicrobial immune responses, while dampening excessive adaptive responses and inflammation to maintain self-tolerance and prevent auto-immunity (Lang et al 2013). During pregnancy, vitamin D is thought to enhance innate anti-microbial and anti-inflammatory responses within the placenta and reproductive tissues, which may protect the fetus from intrauterine infection and subsequent inflammation (Grayson and Hewison 2011).…”

Vitamin D and Immune System

“…The mDCs are professional APCs [78] and the pDCs are more closely associated with immune tolerance [79,80] All cells of innate immunity are capable of; identifying and removing foreign substances present in organs, tissues, into the blood and lymph stream; interacting with pathogens and with each other and modulating the adaptive immune response by regulating timing, type, and number of cytokines [81].…”

“…Active Vitamin D has immune modulatory effects in CKD patients which will ameliorate renal fibrosis and slow-down proteinuria development. This can be done by enhancing Th2 cell differentiation, decreasing IL-6 expression, decreasing inflammatory and oxidative stress, altering T cell behavior, thus favoring tolerance development and reduce proinflammatory activity (140,(143)(144)(145).…”

“…The potential role of Vitamin D in host resistance to infections was based on the following four findings: conversion of circulating Vitamin D to the active Vitamin D requires the CYP27B1 enzyme (cytochrome 27B1, 25-hydroxyvitamin D 3 1-α-hydroxylase) and the immune system is able to produce this enzyme; the majority of immune system cells express VDR especially after stimulation; the production of active Vitamin D in the immune system led to the induction of antibacterial products such as cathelicidin which in turn inhibited the replication of Mycobacterium tuberculosis in vitro; and impaired Vitamin D status is a common health problem across the globe and may be responsible for the increased incidence of common infectious diseases across the world [28,42,81].…”