The research, published Monday in the journal JAMA Pediatrics, supports the current consensus among medical professionals that delaying the introduction of nuts, milk, fish, shellfish, eggs and other highly allergenic foods in young children doesn’t prevent the development of food allergies, said Michael C. Young, associate clinical professor of pediatrics at Harvard Medical School, and a senior author of the study.
The findings inversely link a pregnant mother’s consumption of peanuts or tree nuts with the onset of nut allergies in her child. The more nuts the mother ate while pregnant, or within a year before or after pregnancy, the lower the risk that the child would go on to develop nut allergies, Dr. Young said. The study doesn’t demonstrate a causal relationship between a pregnant mother’s diet and the onset of nut allergies in her offspring, he said.
The researchers stopped short of advising pregnant women to eat more nuts. Further, interventional studies—in which researchers would separate participating pregnant women into groups and prescribe their diets, rather than simply track their consumption—are required before they can make such a recommendation.
Researchers led by A. Lindsay Frazier of the Dana-Farber/Boston Children’s Cancer and Blood Disorders Center in Boston, analyzed data from 8,205 children born between Jan. 1, 1990 and Dec. 31, 1994 to mothers who had reported their diets at or around the time of pregnancy. Of the children they tracked, 140 had developed a peanut or tree nut allergy by 2009. All self-reported cases of physician-diagnosed nut allergies were reviewed independently by two pediatricians, according to the study.
The prevalence of childhood peanut allergy in the U.S. has become an “epidemic” in recent years, Dr. Young said. The rate of 1.4% in 2010 is more than triple the rate of 0.4% in 1997, according to the study. Peanut and tree nut allergies tend to overlap, and such allergies typically become evident with a child’s first known exposure to peanuts or tree nuts, the study said. It defines tree nuts as walnuts, almonds, pistachios, cashews, pecans, hazelnuts, macadamias and Brazil nuts.
Until recently, the American Academy of Pediatrics had recommended that young children avoid eating peanuts and tree nuts until at least age 3 and cautioned pregnant or nursing women against eating peanuts. In 2008, AAP did away with those guidelines after further studies showed little support for them. The new data support the AAP’s move to rescind the recommendation, Dr. Young said. The research “supports the hypothesis that early allergen exposure increases the likelihood of tolerance and thereby lowers the risk of childhood food allergy,” the study said.
Limitations of the study include that the dietary questionnaires weren’t specific to the dates of the mothers’ pregnancies. Only 45% of the questionnaires were completed during pregnancy, and 76% within one year.
In an editorial also published Monday in JAMA Pediatrics, Ruchi Gupta, associate professor of pediatrics at the Northwestern University Feinberg School of Medicine, counseled pregnant mothers against avoiding nuts for fear of causing their children to develop nut allergies. “Certainly, women who are allergic to nuts should continue avoiding nuts,” she added.
“Mothers-to-be should feel free to curb their cravings with a dollop of peanut butter!” Dr. Gupta wrote.