In utero vitamin D exposure reduces childhood allergic rhinitis risk

Results of a recently published study show higher intake of food-based vitamin D by expectant mothers reduces the risk of childhood allergic rhinitis.¹

The investigators analyzed data from 1248 mother-child pairs enrolled in a prospective prebirth cohort study. Based on information derived through maternal reports, the prevalence of ever allergic rhinitis at school age was 23.8%.  “Ever allergic rhinitis at school age” was defined as positive if a mother answered yes to ‘‘Have you ever been told by a health care professional, such as a doctor, physician assistant or nurse practitioner, that your child has hay fever, seasonal allergies or allergic rhinitis (runny nose due to allergies)?’’ at the school-age interview.

Analyses using multivariable-adjusted logistic regression models showed that the risk of a woman having a child with allergic rhinitis by school age fell about 20% per 100 IU/day increase in food-based vitamin D intake during the first and second trimesters of pregnancy. The risk of ever allergic rhinitis in a child was not affected by maternal intake of supplemental vitamin D nor was it associated with maternal vitamin D exposure as measured by serum 25(OH)D levels.

Lead author, Supinda Bunyavanich, MD, MPH, MPhil, told Contemporary Pediatrics, “Based on the findings of our study, physicians might counsel expectant mothers to consider including foods containing vitamin D in their diet during pregnancy. There are not many downsides to consuming these foods, which would include fish, dairy products, egg, and cereals, as they are part of a balanced diet, and a potential benefit may be a reduced risk of allergic rhinitis for their child.”

Dr Bunyavanich is an Assistant Professor in the Departments of Pediatrics and Genetics and Genomic Sciences at the Icahn School of Medicine at Mount Sinai, New York. She noted that because the study was based on mother-child pairs not selected for any disease or condition, its findings are relevant to the general population. For that reason, the dietary advice could be offered to all expectant mothers and there is no reason for it to be targeted to those with a personal or family history of allergic rhinitis.

Rational results

There is good biologic plausibility for an association between in utero exposure to vitamin D and childhood allergy, especially when the exposure occurs earlier during pregnancy, considering that vitamin D affects the immune system and early pregnancy is a formative period of immune system development in the fetus. The fact that food-based vitamin D intake predicted childhood allergic rhinitis risk whereas supplemental vitamin D intake did not may be explained by a contributing role of other nutrients in vitamin D-containing foods.

Now, Dr Bunyavanich and colleagues believe further investigation is warranted to explore the association between vitamin D intake during pregnancy and allergic rhinitis risk in offspring. She noted that other researchers from their team recently published results from the Vitamin D Antenatal Asthma Reduction Trial (VDAART) that was designed to investigate whether prenatal vitamin D supplementation in expectant mothers at risk of having children with asthma affected that outcome.² In VDAART, which was a double-blind, placebo-controlled trial, 881 pregnant women were randomized to receive 4000 IU vitamin D plus prenatal vitamin containing 400 IU vitamin D, or placebo plus prenatal vitamin containing 400 IU vitamin D. Outcomes analyses from follow-up through 3 years of age showed that the incidence of physician-diagnosed asthma or recurrent wheezing was 6.1% lower among children of mothers receiving supplementation with 4000 IU vitamin D compared with controls, but the treatment-related difference was not statistically significant.

“VDAART may have lacked adequate power to detect a statistically significant difference in the incidence of asthma at age 3 years, but follow-up of the study cohort is ongoing,” said Dr Bunyavanich.

“As a follow-up to our study, a prospective trial to further investigate the effect of vitamin D intake during pregnancy and the outcomes of allergic rhinitis and allergen sensitization might involve randomizing expectant mothers to a diet rich in foods containing vitamin D or to a usual diet and then following their children for allergy outcomes over time.”

References

1. Bunyavanich S, Rifas-Shiman SL, Platts-Mills TA, Workman L, Sordillo JE, Camargo CA Jr, Gillman MW, Gold DR, Litonjua AA. Prenatal, perinatal, and childhood vitamin D exposure and their association with childhood allergic rhinitis and allergic sensitization. J Allergy Clin Immunol. 2016 Feb 10.

2. Litonjua AA, Carey VJ, Laranjo N, et al. Effect of prenatal supplementation with vitamin D on asthma or recurrent wheezing in offspring by age 3 years: The VDAART randomized clinical trial. JAMA. 2016;315(4):362-370.