If peanut allergies are on the increase, one perfectly reasonable conclusion might be to avoid eating them while you're pregnant. Some mums also avoid wheat and dairy.... but a recently published study suggests that the opposite might be true.
Researchers from the Harvard Medical School looked at the associations between a pregnant mum's consumption of common childhood food allergens during early pregnancy, and the development of childhood allergy and asthma. They monitored the foods that 1277 healthy pregnant mothers ate during the first six months of their pregnancies. The researchers then followed up by examining their children at around 7 years old.
They checked the children for the development of food allergy, asthma, allergic rhinitis, and atopic dermatitis. Then they examined the associations between the mother's diet during pregnancy and childhood allergy and asthma. They found that a food allergy was common (5.6%) by mid-childhood, as was sensitisation to at least 1 food allergen (28.0%). However, if the mother had eaten a lot of peanuts during the first three months of pregnancy the chance of their child having an peanut allergic reaction reduced by 47%. Higher milk intake was associated with a 15% reduction in asthma and allergic rhinitis. They also found that eating wheat products during the second trimester (months 4-6) reduced the likelihood of the child developing atopic dermatitis (eczema). They did not find any link between eating eggs or soy products.
The researchers concluded that a higher intake of peanut, milk, and wheat by a new mum during early pregnancy significantly reduced the odds that their child would suffer from a mid-childhood allergy and asthma. It seems that an early encounter by the developing baby with food allergens in their mother's diet (via the placenta) during the critical period of immune system formation in early pregnancy, can lead to a tolerance of allergens rather than sensitisation.
They reported that although many healthcare professionals think that restricting certain foods by the mother during pregnancy and breastfeeding, and delaying the introduction of allergenic foods to infants, can prevent allergies and asthma, that systematic reviews do not support this belief. In fact, it seems that there is accumulating evidence that the early introduction of peanut, egg, wheat, milk, and fish to a baby's diet—rather than delaying or avoiding them — may be more helpful as it encourages a tolerance rather than an allergy.
Bunyavanich S, Rifas-Shiman SL, Platts-Mills TA, Workman L, Sordillo JE, Camargo CA Jr, Gillman MW, Gold DR, Litonjua AA. Peanut, milk, and wheat intake during pregnancy is associated with reduced allergy and asthma in children. J Allergy Clin Immunol. 2014 May;133(5):1373-82. doi: 10.1016/j.jaci.2013.11.040.