| Abstract: | In multivariate analyses, every 100-IU increase in maternal vitamin D intake was associated with about a 10% lower risk for any wheeze (odds ratio 0.90) and with nearly a 20% lower risk of having a child at high risk for asthma (OR 0.82). This inverse association was present whether vitamin D came from diet or nutritional supplements and remained after controlling for 10 confounding factors, Dr. Carlos A. Camargo Jr. reported at the annual meeting of the American Academy of Allergy, Asthma and Immunology.
The best explanation for the observed protective effect is that vitamin D, which is known to have some immunologic effects, influences IL-10 secretion by regulatory T cells. The findings suggest that vitamin D insufficiency is a reality, particularly in northern parts of the USA. The mean vitamin D intake during pregnancy was 548 IU/day in the study, which included 1,194 mother-child pairs in Project Viva, a prospective prepartum cohort study in Massachusetts. Intake was assessed using a validated food questionnaire in the first and second trimesters and was averaged for analyses.
The authors defined any wheeze as a mother-reported wheeze or physician-diagnosed asthma, wheezing, or reactive airway disease at ages 1, 2, or 3 years. High risk of asthma was defined as the subset of children with two or more reports of wheezing at 1, 2, or 3 years, plus either parental history of asthma or child diagnosis of eczema.
Multivariate analyses were performed controlling for gender, birth weight, income, maternal age, prepregnancy body mass index, passive smoking exposure, breast-feeding duration at 1 year, number of children younger than 12 in the household, and maternal and paternal history of asthma.
The adjusted risk was significantly lower for any wheeze at age 3 years in children born to 298 women with the highest vitamin D intake, or about 724 IU/day, than in children born to 298 women with the lowest intake, or about 356 IU/day (OR 0.58 vs. 1). The chance of having a child at high risk of asthma at age 3 years also was significantly lower among the high-intake group (OR 0.41 vs. 1).
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