So long as they don’t have nut allergies themselves, pregnant women shouldn’t be afraid that eating nuts might trigger allergies in their child, according to a large new study. In fact, when women ate nuts more than five times a month during pregnancy, their kids had markedly lower risk of nut allergies compared with kids whose mothers avoided nuts, researchers found.
“The take-home message is that the previous concerns or fears of the ingestion of nuts during pregnancy causing subsequent peanut or nut allergy is really unfounded,” said Michael Young, the study’s senior author and an attending physician in allergy and immunology at Boston Children’s Hospital.
But he cautioned that pregnant women shouldn’t start eating peanuts and tree nuts to prevent their children from developing nut allergies. “Even though our study showed a reduction of risk, I really have to emphasize that the way our study was done only shows an association,” he said.
He and his colleagues write in JAMA Pediatrics that between 1997 and 2010, the prevalence of peanut allergies tripled, to 1.4 percent of U.S. children.
The researchers used data from a national study of female nurses between the ages of 24 and 44 years old. Starting in 1991, the women periodically reported what they ate. The researchers then combined information on the women’s diets from around the time of their pregnancies with data from another study of their children.
In 2009, the women completed a questionnaire that asked whether their children had any food allergies. Of 8,205 children in the study, 308 had food allergies, including 140 who were allergic to peanuts or tree nuts. Tree nuts include walnuts, almonds, pistachios, cashews, pecans, hazelnuts, macadamias and Brazil nuts.
Overall, the researchers found that eating nuts while pregnant was not tied to an increased risk of nut allergies among children. On the contrary, the more nuts women reported eating during pregnancy, the less likely their children were to have nut allergies.
About 1.5 percent of children of women who ate less than one serving of nuts per month during pregnancy developed nut allergies. That compared with about 0.5 percent of children of women who ate five or more servings per week.
In other words, kids whose mothers ate nuts most often had about a third of the risk of kids whose mothers ate nuts least often.
The exception was children of women who themselves had a history of nut allergies. In those cases, when women ate nuts five or more times a week during pregnancy, their children had about 21 / 2 times the risk of nut allergies compared with the kids of allergic mothers who avoided nuts during pregnancy.