Vitamin D Supplementation During Pregnancy May Reduce Risk of Childhood Asthma

• A review of 15 years worth of study data has found that taking vitamin D supplements during pregnancy may reduce the risk of asthma and wheezing in children.
• Given the lack of vitamin D among many pregnant women who do not use supplements, experts say this research supports the idea of increasing daily vitamin D3 intake starting from conception.
• The new research is in contrast to past studies in which researchers concluded that vitamin D supplementation during pregnancy was not highly effective.

New research published in The Journal of Allergy and Clinical Immunology reinforces the association between prenatal vitamin D levels and the risk of wheezing and asthma in children.

The analysis, involving 15 years of data from the Vitamin D Antenatal Asthma Reduction (VDAART) clinical trial, demonstrated that administering vitamin D supplements to pregnant women decreased the incidence of asthma and wheezing in their children when compared to children whose mothers were given standard prenatal vitamins.

Scott Weiss, the first author of the study and an associate director of the Channing Division of Network Medicine at Brigham Women’s Hospital as well as a professor at Harvard Medical School in Massachusetts, explained the key findings to Medical News Today by saying that “vitamin D3 given to pregnant women in a dose of 4,400 IU/day resulted in less asthma in their offspring compared to women who took 400 IU/day.”

This is important, he said, as “most pregnant women are deficient in their intake of vitamin D3.”

“Taken together with other pregnancy trials of vitamin D, we would recommend that all pregnant women take a dose of vitamin D3 of 4,000 to 6,000IU/day from conception throughout pregnancy,” Weiss added.

Based on their findings, experts suggest that pregnant women should consider consuming at least 4,400 IU of vitamin D3 daily from the start of their pregnancy.

Vitamin D, obtainable through sunlight exposure, diet, or supplementation, is primarily known for its importance in bone health, but it also plays a role in helping manage autoimmune and other diseases.

The new review established a connection between vitamin D deficiency and increased risks of asthma and wheezing in children.

The relationship between vitamin D levels during pregnancy and childhood asthma has been a subject of debate.

Some past studies have indicated that higher prenatal vitamin D levels might offer protection against asthma.

However, results from a research analysis focusing on vitamin D supplementation during pregnancy did not definitively show a difference between children of supplemented and non-supplemented mothers.

In this latest research, scientists pointed out that an initial VDAART trial and its analyses, along with other meta-analyses on vitamin D supplementation during pregnancy, fail to account for the differences between observational studies and clinical research.

The researchers noted that in the original VDAART study, pregnant women with a family history of allergies or asthma were recruited between 10 and 18 weeks of gestation.

Half of these women received a supplemental dose of 4,400 IU of vitamin D on top of the 400 IU found in their prenatal vitamins, while the other half were given placebos in addition to their prenatal vitamins.

The VDAART results for 3-year-olds indicated a small decrease in asthma incidence among the treatment group, although the difference wasn’t statistical significant.

By the time the children reached age 6, the findings were even less significant.

Yet, upon stratifying the outcomes based on the vitamin D levels in the control group, both sets of analyses gained significance.

Adjusting for the initial vitamin D levels, the researchers observed the anticipated effect seen in observational studies — a 50% reduction in the occurrence of asthma and wheezing.

Drawing on the insights from the VDAART study, the researchers in the new study propose that any future clinical trial should commence as early in pregnancy as feasible, recommend a vitamin D supplementation of 6,000 IU, and emphasize the importance of enrolling a substantial number of women of color.

They said such studies could enhance the comprehension of vitamin D’s potential effects on pregnancy outcomes and the development of asthma in early childhood.

Dr. Raj Dasgupta the chief medical advisor for Sleep Advisor who was not involved in the study, told Medical News Today that the results of the research are interesting.

These results hint at a potential connection between increased vitamin D supplementation for pregnant women and a reduced risk of childhood asthma for the fetus.

Dr. Raj Dasgupta

Dasgupta noted that this the research showed how higher doses of vitamin D during pregnancy are associated with a reduced risk of asthma in children at ages 3 and 6, along with improvements in allergies and lung function.

However, Dasgupta emphasized the need for further research to validate these findings and assess their safety and efficacy for all pregnant women, taking into account individual health circumstances.

Lauren Mahesri, RDN, LD, a pediatric dietitian who also was not involved in this research, told Medical News Today that “this [study] shines a new light on an important topic in maternal and child nutrition.”

“The findings of vitamin D status impacting rates of asthma are critical because both female vitamin D deficiency and childhood asthma are extremely common,” she said.

“One recent study even found that 50 percent of women over 40 years old have some form of vitamin D insufficiency,” Mahesri noted.

One of the biggest implications from this study was that higher vitamin D supplementation, particularly at a dose of 4,400 IU/day, may produce benefits beyond the standard prenatal multivitamin with vitamin D (400 IU/day) in reducing the risk of asthma in their offspring.

Lauren Mahesri, RDN, LD

“This should encourage dietitians and healthcare providers to reassess their pregnant patient’s vitamin D status throughout pregnancy, and supply them with adequate supplementation,” Mahesri said.

“This research also highlights the importance of maternal nutrition during pregnancy and its impact on the long-term health outcomes of children,” she said.

“This emphasizes the importance of evidence-based recommendations for prenatal nutrition and supplementation,” Mahesri explained.