High-dose vitamin D during pregnancy favourably affects immune system of neonates
Vitamin D supplementation during pregnancy positively influences the immune system of the neonate, with the modified immune system potentially being better equipped to protect the host against pathogenic infections, according to a study.
Using a subset of cord blood samples from a randomized placebo-controlled clinical trial (the Vitamin D Antenatal Asthma Reduction Trial), researchers examined the effect of maternal vitamin D3 supplementation of 4,400 IU/d (n=26) vs 400 IU/d during the second and third trimesters of pregnancy.
Assessments included immune cell composition by flow cytometry, Toll-like receptor (TLR) expression by quantitative PCR, and cytokine secretion after stimulation with mitogenic, TLR and T-cell stimuli by cytometric bead array. Responsiveness to the glucocorticoid dexamethasone was also evaluated.
Compared with daily supplementation of 400 IU of vitamin D3, supplementation with the 4,400 IU dose resulted in an improved broad-spectrum proinflammatory cytokine response of cord blood mononuclear cells to innate and mitogenic stimuli (p=0.0009), with an average increase of 1.7- to 2.1-fold in levels of several proinflammatory cytokines (GM-CSF, IFN-γ, IL-1β, IL-6 and IL-8) across stimuli.
Mothers who received the daily 4,400 IU vitamin D3 dose also exhibited a higher gene expression level of TLR2 (p=0.02) and TLR9 (p=0.02), a greater than fourfold increase in IL-17A (p=0.03) production after polyclonal T-cell stimulation, and an enhanced IL-10 response of cord blood mononuclear cells to dexamethasone treatment in culture (p=0.018).
The present data suggest that the 4,400 IU/d regimen may increase mean maternal circulating 25(OH)D levels into the sufficiency range (>30 ng/mL) and that supplementation with the current recommended daily intake of 400 IU/d may not help improve 25(OH)D levels in the mother, researchers said.
“Notably, even within the small cohort studied here, a significant increase in newborn weight and height was observed in babies born to mothers supplemented with 4,400 IU/d. Importantly, supplementation of pregnant women with 4,000 IU/d vitamin D3 appears to be safe and effective in reducing the comorbidities of pregnancy,” they continued. [J Bone Miner Res 2011;26:2341–2357; J Steroid Biochem Mol Biol 2013;136:313–320]
“Given the evidence for strong neonatal immune responses in early life being associated with decreased development of asthma, this effect will likely lead to improved respiratory health in early life. Future studies should address the longitudinal effect of vitamin D3 supplementation in pregnancy on clinical and immune outcomes in the infant,” researchers concluded.