Vitamin D in pregnancy may reduce the risk of childhood asthma

The sunshine vitamin is well known for its crucial role in making bones healthy and strong. As well as helping the body to absorb calcium, Vitamin D is important in the regulation of both adaptive and innate immune system responses.

Evidence suggests that Vit D could reduce severe asthma attacks when taken alongside standard asthma treatment [1]. Plus, a recent review showed that Vit D supplements could help to prevent acute respiratory tract infections known to aggravate asthma [2].

Many recent studies are finding connections between low D levels in expectant mothers and an increased risk of asthma and respiratory infections in newborns. This suggests that taking D supplements during pregnancy could be the key to preventing asthma in infants.

What does new research tell us?

A new study published in the Journal of Allergy and Clinical Immunology found that taking Vitamin D during pregnancy positively influences the immune system of the fetus. Ultimately, this could reduce the risk of asthma and respiratory infections in newborn babies. Researchers found that asthma is usually diagnosed in early childhood, implying that the condition originates in the fetus or during early life.

Half of the participants in the study group were given a high dose of 4,400 IU of Vitamin D3 daily during the second and third trimesters of pregnancy. The remaining participants took the recommended daily intake of 400 IU.

The research team analyzed the umbilical cord blood to test the response of innate and adaptive immune systems when the blood was exposed to simulated pathogens. Innate or natural immunity works short-term, whereas adaptive immunity utilizes specialized immune cells (T-lymphocytes) to launch a fierce attack against pathogens, providing long-term protection.

Unsurprisingly, the researchers found that blood samples from babies born to women who took higher doses of Vit D showed improved response to infections. The study concluded that “Vitamin D exposure during foetal development influences the immune system of the neonate, which can contribute to protection from asthma-related, including infectious, outcomes in early life.” [3]

Most of the evidence regarding low maternal Vit D levels and risk of neonatal asthma is reported by observational and cohort studies. Though supportive, these studies are considered inconclusive. Therefore, results from a randomized, double-blind, placebo-controlled clinical trial like this lend more weight and a flicker of positivity to the role of Vitamin D in preventing asthma in early childhood and also to improve outcomes later in life.

Lead researcher Professor Catherine Hawrylowicz from King’s College London said: “Studies to date that have investigated links between Vitamin D and immunity in the baby have been observational. For the first time, we have shown that higher Vit D levels in pregnancy can effectively alter the immune response of the newborn baby, which could help to protect the child from developing asthma. Future studies should look at the long-term impact on the immunity of the infant.” [4]

While the effect of Vit D during pregnancy on neonatal immunity seems promising according to this study, experts believe that more research is required to establish whether this dose can also help to lower asthma-related risks later in life.

However, these findings are in sync with what previous prenatal studies tell us regarding the impact of Vit D levels on the respiratory health of offspring.

A recent study published in Paediatrics Infectious Disease Journal also supports a preventative role of Vitamin D during pregnancy on offspring wheezing and respiratory tract infections [5].

Another analysis also concluded that maternal supplementation of Vit D leads to a reduced rate of asthma and recurrent wheezing in young children, suggesting that “higher vitamin D status beginning in early pregnancy is necessary for asthma/recurrent wheeze prevention in early life.” [6]

But exactly why is Vitamin D important during pregnancy?

Vitamin D modulates the immune system, works as an anti-inflammatory, and is involved in the production of antimicrobial proteins in the body that fight bacterial and viral infections. Vit D reserves of a new-born depend on maternal vitamin levels. Therefore, increasing Vit D pregnancy supplementation likely benefits newborns by reducing their risk of recurrent wheezing, respiratory infections, and asthma.

You may be wondering, “great, but is Vitamin D safe during pregnancy?”

Considering Vit D has a low toxicity index, supplementation is considered a safe and effective strategy for pregnant women. Vit D for pregnancy is especially helpful if the mother is deficient and therefore at a high risk of giving birth to a child with asthma.

  1. Martineau et al. Vitamin D for the management of asthma. Cochrane Library. 2016.
  2. Martineau et al. Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ, 2017
  3. E Hornsby et al. Vitamin D supplementation during pregnancy: Effect on the neonatal immune system in a randomized controlled trial. The Journal of Allergy and Clinical Immunology. 2017
  4. Vitamin D in pregnancy may help prevent childhood asthma. King’s College London. 2017
  5. Christensen N, Søndergaard J, Fisker N, Christesen HT. Infant Respiratory Tract Infections or Wheeze and Maternal Vitamin D in Pregnancy: A Systematic Review. Pediatr Infect Dis J. 2017
  6. Wolsk HM et al. Vitamin D supplementation in pregnancy, prenatal 25(OH)D levels, race, and subsequent asthma or recurrent wheeze in offspring: Secondary analyses from the Vitamin D Antenatal Asthma Reduction Trial. The Journal of Allergy and Clinical Immunology. 2017