Vitamin D supplementation during pregnancy, infancy associated with less asthma, wheeze

Key takeaways:

• Children of mothers who had high-dose prenatal vitamin D and who had sufficient vitamin D at age 12 months had the least frequent asthma and wheeze.
• These findings may inform optimal timing for supplementation.

WASHINGTON — Vitamin D supplementation during pregnancy and sufficient exposure to vitamin D at age 12 months were associated with less asthma and recurrent wheeze by age 3 years, according to data presented here.

Various factors contribute to the development of childhood asthma, and data on the role of early life nutritional exposures modifying this risk are evolving, Lourdes G. Ramirez, MD, allergy and clinical immunology fellow, Brigham and Women’s Hospital, told Healio.

“Several observational studies have shown an association of higher vitamin D status prenatally and in early life as protective for childhood asthma,” Ramirez said.

In the Vitamin D Antenatal Asthma Reduction Trial (VDAART), the researchers found an association between maternal high-dose vitamin D supplementation in pregnancy and reduced offspring asthma or recurrent wheeze at age 3 years.

“This current study, a secondary analysis of the VDAART results, was prompted by our interest in understanding the optimal timing of vitamin D supplementation on childhood asthma protection and whether prenatal and/or early postnatal life vitamin D supplementation impact asthma development differently,” Ramirez said.

Study design, results

In this secondary analysis, the results of which were presented at the American Thoracic Society International Conference, the researchers classified participants into four groups based on maternal randomization to high or standard doses of vitamin D supplementation during pregnancy and sufficient offspring exposure to vitamin D at age 12 months.

High doses of vitamin D supplementation were defined as 4,400 IU per day, and standard doses were defined as 400 IU per day. Also, sufficient offspring exposure was defined as doses of vitamin D or multivitamin drops at least 5 days a week or 32 ounces or more of infant formula each day.

The “both” group (n = 133) included infants whose doses of vitamin D were high among their mothers and sufficient for themselves. The “neither” group (n = 227) included infants whose doses were standard among their mothers and insufficient among themselves.

Also, the “mother only” group (n = 236) included infants whose doses were high among their mothers but insufficient among themselves. The “infant only” group (n = 142) had mothers with standard doses and sufficient doses among themselves.

“Consistent with prior evidence, we found that offspring whose mothers received high-dose vitamin D supplementation during pregnancy had reduced asthma/wheeze at 3 years,” Ramirez said.

“In children who did not receive high-dose vitamin D prenatally and consumed less than 32 ounces per day of vitamin D-fortified infant formula by age 6 months (the equivalent of 400 IU vitamin D daily), supplementation with vitamin D drops of 400 IU per day was associated with reduced atopic asthma at 6 years of age,” she continued.

Although asthma or recurrent wheeze was least frequent among the infants in the “both” group, the researchers said that this difference did not reach statistical significance.

The adjusted odds ratio for asthma or recurrent wheeze by age 3 years was 0.73 (95% CI, 0.35-1.52) for the “mother only” group vs. the “neither” group. Also, adjusted odds ratios included 1.04 (95% CI, 0.5-2.15) for the “infant only” group vs. the “neither” group, and 0.51 (95% CI, 0.24-1.08) for the “both” group vs. the “neither” group.

The “both” group additionally had significantly less atopy by age 6 years compared with the “neither” group, with an adjusted odds ratio of 0.23 (95% CI, 0.06-0.8). Adjusted odds ratios also included 0.63 (95% CI, 0.27-1.45) for the “mother only” vs. the “neither” group, and 0.65 (95% CI, 0.18-2.07) for the “infant only” vs. the “neither” group.

Conclusions

These findings indicate associations between reduced asthma with atopy by age 6 years and high-dose vitamin D supplementation during pregnancy and sufficient offspring exposure at age 12 months as well as with reduced asthma and recurrent wheeze by age 3 years, although this association was not significant.

Based on these results, the researchers said that vitamin D may have a role in asthma prevention and could provide insight into the optimal timing for supplementation.

“These data support the notion that both prenatal and postnatal vitamin D supplementation is important in childhood asthma prevention,” Ramirez said. “These results highlight the need to maintain adequate vitamin D status in early life.”

Specifically, Ramirez said these findings indicate the need to follow guidance from the American Academy of Pediatrics recommending 400 IU of daily vitamin D for infants aged 12 months and younger, especially for those with a family history of atopy and those who primarily are being breastfed.

“In addition, supplementation with high-dose vitamin D in pregnancy (up to 4,400 IU daily) may offer protection in the development of offspring asthma/recurrent wheeze by 3 years of age,” Ramirez said.

“Future steps in this research will focus on the immune modulatory effects of prenatal vitamin D supplementation and their association with childhood asthma outcomes,” Ramirez said.

References:

• Litonjua AA, et al. JAMA. 2016;doi:10.1001/jama.2015.18589.
• Wolsk HM, et al. PLoS One. 2017;doi:10.1371/journal.pone.0186657.

For more information:

Lourdes G. Ramirez, MD, can be reached at lgramirez@bwh.harvard.edu.