Study results published in Allergy suggest that supplementing pregnant women with vitamin D may increase their children's risk for developing food allergy in infancy.
The team hopes the findings will help clarify the effects of vitamin D levels on symptoms of allergy in children, as results from previous studies have been conflicting, with some showing allergic symptoms associated with high vitamin D levels in pregnant women and children and some with low levels.
Irina Lehmann (University of Leipzig, Germany) and colleagues assessed levels of vitamin D in the blood of 378 women during pregnancy and in the cord blood of their babies at birth. The women were all participating in the Lifestyle and environmental factors and their Influence on Newborns Allergy risk (LINA) cohort study.
As well as data on vitamin D status, the researchers collected information about any atopic manifestations displayed by the children during the first 2 years of life through parental questionnaires and by testing allergen specific Immunoglobulin (Ig)E levels at the age of 2 years.
They found that women in the highest quartile for vitamin D during pregnancy (32.20-60.80 ng/mL) were a significant 3.66-fold more likely to have a child who developed food allergy during their second year of life than those in the bottom quartile (6.13-14.39 ng/mL), following adjustment for various confounders including family atopy history, cotinine level in pregnancy, and vitamin D supplementation in first year of life.
Children of mothers in the highest quartile for vitamin D status in pregnancy also had a significant 1.91-fold increased risk for food allergy within the first 2 years of life compared with children of mothers in the bottom quartile for vitamin D, as well as a 1.59-fold increased risk for having food-specific IgE antibodies.
Children with the highest levels of vitamin D (17.40-40.10 ng/mL) in their cord blood at birth also had a significant 4.65-fold increased risk for developing food allergy in the second year of life compared with children with the lowest levels (1.50-6.98 ng/mL).
Lehmann and team suggest that an inhibition of regulatory T cell numbers at birth associated with high levels of vitamin D in the blood may explain the increased risk for food allergy seen in these children.
"Our study demonstrates that high vitamin D levels in pregnancy and at birth may contribute to a higher risk for food allergy and therefore argues against vitamin D supplement to protect against allergy," writes the team.
"It is of high relevance to clarify how vitamin D in the pre- or neonatal period is able to modify programming of future immune function and therefore atopic outcomes later on," they add.
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