Results from the VDAART study showed sufficient prenatal and postnatal vitamin D intake may reduce the risk of atopic asthma in children by the age of 6.

“Studies have demonstrated that high dietary intake of vitamin D during pregnancy is associated with a reduced risk for asthma or recurrent wheezing in young children,” said Lourdes Ramirez, MD, who presented her remarks at the 2023 American Thoracic Society (ATS) International Conference, held May 19-24, in Washington, DC. Given that “the effects of postnatal vitamin D intake on asthma protection are however less clear,” Dr. Ramirez said, she and her colleagues sought to answer the following questions:

• What is the optimal timing for vitamin D supplementation with regard to asthma protection?
• Do prenatal and/or postnatal vitamin D intake have a different influence on the occurrence of asthma?

The randomized Vitamin D Antenatal Asthma Reduction (VDAART) trial included 881 pregnant women whose infants were at high risk for asthma. The primary outcome of asthma or recurrent wheezing at 3 years of age was compared between four exposure groups:

• High prenatal (4,400 IU per day) and postnatal (≥400 IU per day at the age of 12 months) vitamin D supplementation
• Low prenatal (400 IU per day) and postnatal (<400 IU per day) intake
• High prenatal and low postnatal intake
• Low prenatal and high postnatal intake

Infants who had received a sufficient intake of vitamin D, both prenatal and postnatal, had a numerically reduced risk of recurrent wheezing or asthma at age 3 compared with those who did not receive sufficient vitamin D intake, either prenatal or postnatal, but this result did not reach statistical significance (adjusted OR [aOR], 0.51; 95% CI, 0.24-1.08;P=0.08). Infants in the “both” group had numerically improved ORs compared with those in the prenatal only (aOR, 0.73; 95% CI, 0.35-1.52) or postnatal only (aOR, 1.04; 95% CI, 0.50-2.15) group. In addition, atopic asthma at age 6, a secondary outcome measure, occurred less frequently in infants who received sufficient prenatal and postnatal vitamin D supplementation compared with those who did not (aOR, 0.23; 95% CI, 0.06-0.80; P=0.03).

According to Dr. Ramirez, these results give some insight into the optimal timing of vitamin D supplementation with respect to asthma protection.

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