Excessive intakes of vitamin D during pregnancy may increase children’s food allergy risk

A new study from Germany suggests that consuming high doses of vitamin D supplements during pregnancy may raise the risk of children developing food allergies in the first two years of their lives. Experts criticize the findings as not being representative.

Based on results of an earlier observational trial, the blood vitamin D concentrations of 622 pregnant mothers and their 629 newborn children were compared with the occurrence of food allergies during the first two years of the children’s lives, assessed by questionnaires (1). The study results showed that in cases where expectant mothers were found to have low blood vitamin D levels, the occurrence of food allergies among their two-year-old children was lower than in cases where expectant mothers had high vitamin D blood levels. In addition, children whose mothers had high intakes of vitamin D had high levels of the specific immunoglobulin E to food allergens such as egg white, milk protein, wheat flour, peanuts, or soya beans. Moreover, high concentrations of 25(OH)D3 in cord blood were associated with lower numbers of regulatory T cells.

Experts criticized the fact that the study’s results also showed that, of all the pregnant mothers, 44.4% had deficient (below 20 ng/ml), 25.7% had insufficient (20–29.9 ng/ml), and only 29.9% had optimal (beyond
30 ng/ml) 25(OH)D3 levels. 50.0% of the newborns had deficient 25(OH)D3 levels (below 11 ng/ml). Only seven mothers obtained vitamin D supplements during pregnancy. Several epidemiological studies have shown that many pregnant women worldwide have insufficient or deficient vitamin D levels, which subse-quently result in insufficient or deficient vitamin D levels in newborns. To reduce disease risks related to low vitamin D levels in mother and child, supplementation in adequate doses is recommended by the majority of scientists. While warning against overly high vitamin D intakes is plausible, as is the case for any nutrient, it does not reflect the reality of widespread insufficient intakes.

Commenting on a potential mechanism, the researchers said that vitamin D may suppress the development of certain regulatory immune T cells (Treg), which are capable of preventing the immune system from over-reacting to allergens, with the result that they protect against allergies. Thus, by reducing the immune regu-lator cells’ activity, vitamin D could increase the risk of allergy. The scientists conceded that the occurrence of food allergies is undoubtedly affected by many factors other than just the vitamin D level but stated that it is important to take this factor into consideration.

1. Weisse K. et al. Maternal and newborn vitamin D status and its impact on food allergy development in the German LINA cohort study. Allergy. 2013; 68:220–228.