Mom’s Extra Egg, Peanut Intake Doesn’t Reduce Baby’s Allergy Risk

Women who ate a diet high in eggs and peanuts during pregnancy and lactation did not lower their baby’s risk of allergies to those foods at 1 year in a clinical trial among families with a history of allergies.

Randomization to eat at least six eggs and 60 peanuts per week from before 23 weeks’ gestation until 4 months postnatally during lactation didn’t change the proportion of infants with immunoglobulin E (IgE)-mediated egg or peanut allergy compared with mothers eating a standard diet that included no more than three eggs and 30 peanuts a week (7.8% vs 8.4%; relative risk [RR] 0.93, 95% CI 0.69-1.26, P=0.65).

“There were also no indications that higher maternal egg and peanut ingestion reduced (or increased) the risk of infant egg or peanut sensitization, IgE-mediated egg allergy, IgE-mediated peanut allergy, or medical diagnosis of eczema,” the researchers, led by Debra J. Palmer, PhD, of the University of Western Australia in Nedlands, reported in the New England Journal of Medicine.

“This finding reinforces the importance of timely introduction of egg and peanut in infant diets,” the group concluded.

After trials showing that timely oral exposure to allergenic foods in early life can promote tolerance changed clinical practice, the question was “whether the window for prevention begins even earlier, during fetal life and breast-feeding, when the developing immune system is first exposed to maternal antigens and dietary proteins,” wrote Maria C. Jenmalm, PhD, of Linköping University in Sweden, in an accompanying editorial. Food-allergen immune responses can show up before infants begin eating solid foods, as babies encounter food proteins in utero and through breast milk.

The clinical message is a practical and reassuring one, she added: “Pregnant and lactating women who tolerate egg and peanut need not avoid these foods for allergy prevention. Equally, they should not feel obliged to consume high quantities of egg or peanut to protect their child. This message is especially important for families with strong allergic histories, who may already have anxiety about infant allergy risk.”

“The trial supports counseling that is permissive rather than prescriptive: maintain a nutritionally adequate, varied diet according to preference and tolerance, and focus prevention advice on timely introduction and ongoing inclusion of allergenic foods in the infant diet when developmentally appropriate,” Jenmalm wrote.

One limitation of the trial was the lower-than-anticipated prevalence of egg or peanut allergy in the high-risk population studied, “which may have reduced our ability to detect an effect of the dietary intervention (although the confidence interval does not rule out the possibility of a clinically important 30% risk reduction),” Palmer’s group wrote. That 16% expected rate (vs the observed 8% rate) had been based on data collected before the 2016 update of Australian guidelines for infant feeding and allergy prevention that emphasized early exposure to potentially allergenic foods, similar to the shift in U.S. guidance.

Both trial treatment groups received advice consistent with those current allergy prevention recommendations, including introduction of egg and peanut in the first year of life. “As a result, the trial may have been conducted in a population already benefiting from improved infant-feeding practices,” Jenmalm agreed. “Nevertheless, the confidence interval and the authors’ confidence-distribution analysis argue strongly against a clinically important preventive effect of high maternal intake.”

The PrEggNut trial included 2,137 pregnant women seen at medical centers across four Australian cities who were at less than 23 weeks’ gestation with a singleton pregnancy and planning to breast-feed for at least 4 months. The women didn’t have egg or peanut allergies themselves, but at least two biologic family members of the fetus (mother, father, or siblings) had to have medically diagnosed allergic disease (asthma, eczema or atopic dermatitis, allergic rhinitis, or IgE-mediated food allergy).

The primary endpoint of percentage of infants with egg or peanut allergy at 1 year of age came out similar in the per-protocol population (5.6% in the high egg and peanut group vs 6.8% in the standard-diet group; RR 0.80, 95% CI 0.48-1.35). The same was true for the two food allergies considered separately: IgE-mediated egg allergy (6.2% vs 7.2%; RR 0.87, 95% CI 0.62-1.21) and IgE-mediated peanut allergy (2.6% in both groups; RR 1.02, 95% CI 0.60-1.76). Medically diagnosed eczema was likewise similar between groups at 4 months of age (16.4% vs 18.1%) and 12 months of age (42.8% vs 46.2%).

“There was also little evidence of effect modification in subgroup analyses,” the researchers added.

Nor were there differences in maternal or infant safety outcomes, including serious adverse events (3.6% high intake vs 3.8% standard diet, P=0.73) and infant anaphylaxis to egg or peanut (0.5% vs 0.9%, P=0.21).