An analysis of pregnant mothers found that children appear to be less at risk for developing peanut or tree nut allergies if their mothers are not allergic and ate more nuts during pregnancy.

In the United States, the prevalence of childhood peanut allergy has more than tripled from 0.4 percent in 1997 to 1.4 percent in 2010. That corresponds with medical recommendations that mothers eat fewer nuts.

Study participants included children born to mothers who previously reported their diet during, or shortly before or after, their pregnancy as part of the ongoing Nurses' Health Study II. Among 8,205 children, researchers identified 308 cases of food allergy, including 140 cases of P/TN allergy. Study findings indicate that children whose nonallergic mothers had the highest P/TN consumption (five times a week or more) had the lowest risk of P/TN allergy. This lower risk of P/TN allergy was not observed among the children of mothers who had a P/TN allergy.

"Our study supports the hypothesis that early allergen exposure increases the likelihood of tolerance and thereby lowers the risk of childhood food allergy. Additional prospective studies are needed to replicate this finding," the study concludes. "In the meantime, our data support the recent decisions to rescind recommendations that all mothers avoid P/TN during pregnancy and breastfeeding."

In a related editorial, Ruchi Gupta, M.D., M.P.H., of the Northwestern University Feinberg School of Medicine, Chicago, writes: "Frazier and colleagues report a strong inverse association between peripregnancy nut intake and the risk of nut allergy in children among mothers who did not have nut allergies.

"Although the dietary surveys were not specific for the actual dates of pregnancy, these findings support recent recommendations that woman should not restrict their diets during pregnancy. Certainly, women who are allergic to nuts should continue avoiding nuts."