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Maternal vitamin D exposure benefits fetal immune system
Vitamin D supplementation during pregnancy modifies the immune system of the neonate in a way that can help protect the host from asthma-related and infectious outcomes in early life, according to findings published in the Journal of Allergy and Clinical Immunology.
“Vitamin D status during pregnancy has been linked to immune parameters in the neonate,” Eve Hornsby, PhD, from the MRC-Asthma UK Centre for Allergic Mechanisms in Asthma at King’s College London, and colleagues wrote. “To our knowledge, all studies to date that have investigated links between vitamin D status and immune outcomes in the neonate have been observational and therefore do not address directly whether vitamin D can actively alter the responsiveness of the neonatal immune system to innate and adaptive challenge.”
To determine the effect of maternal vitamin D supplementation on neonatal immunity during the second and third trimesters of pregnancy, researchers examined a subset of cord blood samples from the double-blind, placebo-controlled Vitamin D Antenatal Asthma Reduction Trial. The investigators randomly provided 26 mothers with 4,400 IU per day and 25 mothers with 400 IU per day of vitamin D3 to analyze for immune cell composition, Toll-like receptor (TLR) expression and cytokine secretion. They also assessed responsiveness to the glucocorticoid dexamethasone.
The 26 mothers supplemented with 4,400 IU of experienced a greater broad-spectrum proinflammatory cytokine response of cord blood mononuclear cells to innate and mitogenic stimuli (P = .0009) than mothers given 400 IU of vitamin D. On average, the increase was 1.7- to 2.1-fold higher in levels of several proinflammatory cytokines across stimuli. Analysis showed a higher gene expression level of TLR2 (P = .02) and TLR9 (P = .02), and a higher than 4-fold increase in IL-17A production after polyclonal T-cell stimulation. In culture, results showed an enhanced IL-10 response of cord blood mononuclear cells to dexamethasone treatment (P = .018).
“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,” Hornsby and colleagues wrote. “Future studies should address the longitudinal effect of vitamin D3 supplementation in pregnancy on clinical and immune outcomes in the infant.” – by Savannah Demko
Disclosures: Hornsby reports no relevant financial disclosures. Please see the full study for a complete list of all other authors’ relevant financial disclosures.
Perspective
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This abstract is a very basic and preliminary effort to look at the effect of vitamin D supplementation on the neonatal immune system. A total of 51 cord blood samples were used for the analysis. It was a small sample size, though there were statistically significant findings. There is no information about the proposed concept that vitamin D supplementation in pregnancy can have a positive effect on the neonatal immune system that reduces the risk of inflammatory diseases such as asthma. Asthma was not an outcome measured in this study. The connection between the immune system effects measured here and asthma are hypothesized, not proven. This study suggests that further research may be appropriate to determine if there are truly any beneficial effects of vitamin D in pregnancy for the fetus. Certainly, no negative effects were discovered.
Personally, I remain dubious that there are any beneficial effects from vitamin D supplementation in pregnancy. I know of several large OB practices that routinely measure vitamin D and supplement when low, and other practices that never measure vitamin D levels, and do not see any differences in outcomes. Of course, we are talking about short-term consequences, not things like asthma later in a child’s life. Similar benefits have been touted in the past for vitamin C, vitamin E and calcium, with no direct benefits ever demonstrated.