Prenatal vitamin D supplementation has no impact on childhood asthma risk
High-dose vitamin D supplementation at 24 weeks of pregnancy was not associated with significant changes in the risk of asthma in offspring at 6 years of age, according to a recent study.
Previous data from the Copenhagen Prospective Studies on Asthma in Childhood 2010, which randomized women to receive high-dose vitamin D (2400 IU/day) or placebo in addition to the recommended intake of 400 IU/day at 24 weeks of pregnancy, showed that either of the two treatment groups was not associated with reduced risk of persistent wheeze in their offspring at 3 years of age. The current analysis is based on the extension trial involving follow-up of 623 women and 545 children up to 6 years of age. [JAMA 2019;321:1003-1005]
“Because diagnosing asthma early in life is difficult, we followed up the children at the age of 6 years to assess the risk of current asthma,” the researchers said.
Among all offspring, asthma was diagnosed in 23 children in the high-dose vitamin D group and 18 children in the placebo group during the first 6 years of life. At 6 years, children born to mothers who received high-dose vitamin D or placebo showed no difference with regard to risk of asthma (8 percent vs 7 percent, adjusted odds ratio [adjOR], 1.21, 95 percent confidence interval [CI], 0.63–2.32; p=0.57).
Similarly, the yearly prevalence of persistent wheeze or asthma was comparable in children born to mothers who were supplemented with high-dose vitamin D or placebo at 6 years (OR, 0.87, 95 percent CI, 0.59–1.28; p=0.48).
“The possible clinically important protective effect of vitamin D on persistent wheeze at the age of 3 years was not found at the age of 6 years,” said the researchers.
There was also no difference in the incidence of lung function and bronchial responsiveness between the two treatment groups, which according to the researchers, “are key elements in asthma pathogenesis”.
Furthermore, no significant differences on allergy outcomes were observed in both treatment groups, as indicated by similar sensitization responses in terms of specific IgE (OR, 1.27, 95 percent CI, 0.84–1.93; p=0.25) and skin prick test (OR, 1.89, 95 percent CI, 0.89–4.02; p=0.10), as well as allergic rhinitis (OR, 1.36, 95 percent CI, 0.70–2.66; p=0.36).
A previous study analysing the link between in utero vitamin D exposure and risk of asthma in their offspring have produced contrasting findings, which showed that low in utero vitamin D levels may be associated with risk of childhood asthma. [J Allergy Clin Immunol 2017;139:1508-1517]
“Future studies should investigate whether the effect of prenatal vitamin D supplementation is modified by environmental, dietary, or genetic factors,” the researchers noted.