November 8, 2010

Expectant moms and peanuts: Maybe not a good idea

Babies born to mothers who eat peanuts during pregnancy appear more prone to peanut allergy, according to research conducted by scientists at Johns Hopkins Children’s Center and elsewhere and published online Oct. 29 in The Journal of Allergy and Clinical Immunology. The research team was led by Scott Sicherer, of the Mount Sinai School of Medicine in New York.

The researchers analyzed the relationship between maternal peanut-eating habits during pregnancy and a child’s sensitivity to peanut proteins. Infants in the study whose mothers reported eating peanuts at least twice a week during pregnancy were nearly three times more likely than other infants to have levels of peanut antibodies high enough to suggest a lurking peanut allergy. Of the 503 infants, 3 to 15 months of age, 28 percent had such blood levels. All infants already had either confirmed or suspected diagnoses of milk or egg allergy.

The investigators emphasize that their work is far from showing a direct cause and effect between a mother’s peanut consumption and her baby’s allergy, and that the affected babies were already more likely to be immunologically susceptible to peanut allergies. The findings do suggest, however, that peanut eating may be a “priming” mechanism—possibly one of several such mechanisms—for developing peanut allergy, the investigators say.

“Mom’s peanut consumption during pregnancy appears to be a key primer for allergy in babies who already have the immunologic predisposition for such, but eating peanuts in and of itself is not enough to cause the allergy,” said Robert Wood, co-author on the study and director of Allergy and Immunology at Johns Hopkins Children’s Center. Indeed, the fact that the children in the study were already allergic to other foods suggests a predisposition to allergies, the investigators emphasize.

While the scientists stop short of recommending complete peanut avoidance during pregnancy, their findings suggest that pregnant women should keep this risk factor in mind when making dietary choices, especially if they have a family history of food allergies.

The investigators also caution that elevated antibody levels are not the same as clinical allergy, even though they are believed to be a potent predictor of future allergies. A food challenge remains the gold standard for clinical allergy, but because of the infants’ young age, such tests were not performed, the investigators say.

Among the 211 children whose mothers reported eating peanuts at least twice a week, 35 percent had significantly elevated antibodies to peanuts, while 22 percent of the 292 infants whose moms consumed peanuts less than twice a week had such high levels.

Whether a mother ate peanuts during breastfeeding did not seem to affect a child’s risk for peanut allergy, nor did the mode of delivery, whether the baby was breast- or formula-fed or whether a baby was fed soy or milk formula, the researchers found.

An estimated 1 percent of U.S. children have peanut allergies, which are often lifelong. Past research suggests that peanut allergies are more severe than other food allergies.

Institutions participating in the study in addition to Mount Sinai and Johns Hopkins were Duke University Medical Center, National Jewish Health Hospital and the University of Arkansas for Medical Sciences.

The research was funded by the National Institutes of Health.