Prenatal Vitamin D Reduces Asthma Risk in Children, Clinical Trial Data Suggests

 Prenatal Vitamin D Reduces Asthma Risk in Children, 

Clinical Trial Data Suggests

A review of 15 years of data from the Vitamin D Prenatal Asthma Reduction Trial (VDAART) found that vitamin D supplementation during pregnancy reduced the incidence of asthma and wheezing in children compared to a standard prenatal multivitamin

A review of 15 years of data from the Vitamin D Prenatal Asthma Reduction Trial (VDAART) found that vitamin D supplementation during pregnancy reduced the incidence of asthma and wheezing in children compared to a standard prenatal multivitamin.

Researchers at Brigham and Women's Hospital (BWH), a founding member of the Massachusetts General Hospital Brigham Healthcare System, have published a new review article highlighting the link between vitamin D levels during pregnancy and childhood wheezing and asthma in children. The review study was published in the Journal of Allergy and Clinical Immunology by the researchers.

"Vitamin D deficiency is common, especially in pregnant women who are not taking supplements," stated Scott T. Weiss, the study's first author, associate chair of the Department of Medicine at Brigham and Women's Hospital Channing Network and professor at Harvard Medical School. "Based on our findings, we recommend that all pregnant women consume at least 4,400 international units of vitamin D3 daily throughout their pregnancy, beginning at conception."

Vitamin D is a nutrient that comes from sun exposure, diet or supplements. It is often considered essential for bone health, but also has a role in autoimmune and other diseases. The review links vitamin D deficiency to childhood asthma and wheezing, a leading cause of disease in young children. About 40 percent of children have daily symptoms of wheezing by age three. By age six, 20 percent of children are diagnosed with asthma.

The link between childhood asthma and vitamin D has been controversial. Observational studies have shown that higher vitamin D levels during pregnancy can prevent asthma. Comparing the vitamin D supplemented group to the unsupplemented group in the Vitamin D Prenatal Asthma Reduction Trial (VDAART), a clinical trial investigating vitamin D supplementation during pregnancy, yielded conflicting results.

"Overall, observational studies showed an effect, but clinical trials did not, because nutritional trials are very different from drug trials," Weiss said. "You're comparing dosage and non dosing in a pharmacological study. In a nutrition trial, you're comparing more and less of a nutrient, but the baseline amount in the control group is variable."

Understanding the role of a nutrient during pregnancy requires consideration of the dose of the nutrient, the time of initiation of administration, and the baseline level in the control group, which Weiss said was overlooked in prior meta-analyses of vitamin D supplementation during pregnancy as well as the initial VDAART study and analysis.

Between 10 and 18 weeks of pregnancy, participants in the initial VDAART research were pregnant women having a family history of allergies or asthma. Half of the women took 4,400 international units of vitamin D in addition to 400 international units of vitamin D in their prenatal vitamins. The other half took a placebo along with their prenatal vitamins.

The results of the VDAART study in three-year-old , published in JAMA in 2016, showed a 20 percent reduction in asthma incidence in the treatment group, which was statistically critically significant. the results of the 2020 study, published in the New Journal of Medicine (NEJM), had an even smaller effect on six-year-olds.

Weiss continued, "But both analyses become important when we stratify the results based on vitamin D levels in the control group." "When you adjust for baseline vitamin D levels, we saw a definite effect in the observational study - a 50 percent reduction in asthma and wheezing."

Weiss's team published a reanalysis at age 3 in Public Library of Science - General in 2017, and published data at age 6 in the American Journal of Clinical Nutrition in 2023. The latest review article summarizes these studies as well as genetic findings that further strengthen the possibility of a causal link between vitamin D and asthma, and offers several considerations for planning follow-up studies.

According to Weiss, "Based on the insights gained from VDAART, we recommend starting a follow-up clinical trial as early as possible in pregnancy, supplementing with 6,000 IU of vitamin D, and seeking very high enrollment rates in women of color." "Such a trial could deepen our understanding of the potential impact of vitamin D on pregnancy outcomes and early asthma."