Children whose mothers ate more peanuts and tree nuts while pregnant are less likely to develop allergies to those foods, according to a study that reverses previous doctor recommendations.
The study from Boston Children's Hospital found that the children of moms not allergic to peanuts and tree nuts who ate five or more servings a week of the foods had a reduced risk of allergies than kids whose mothers ate less than one serving a month. The study is published Tuesday in JAMA Pediatrics.
Previous guidelines from the American Academy of Pediatrics in 2000 recommended avoiding these nuts during pregnancy yet the prevalence of allergies to these foods still tripled from 1997 to 2010, said Michael Young, a senior study author. Studies examining the link were inconsistent, causing the academy to rescind those recommendations in 2008. Tuesday's findings are the first in humans to link increased exposure to peanuts and tree nuts in utero and reduced allergies in children, he said.
"The data do dispel the fear that eating peanuts/tree nuts during pregnancy will cause peanut allergy in the offspring," Young, an attending physician at Boston Children's Hospital in the Division of Allergy and Immunology, said in an e-mail. "So, a pregnant woman who wishes to eat peanuts/tree nuts during her pregnancy can feel free to do so."
Young, who is also an associate clinical professor of pediatrics at Harvard Medical School, said Tuesday's findings support results from other studies suggesting that early exposure to food allergens is needed to develop a tolerance.
Researchers analyzed data from 8,205 children in the Growing Up Today Study, whose mothers were part of the Nurses' Health Study II and provided information about their diet before, during and after pregnancy. They found 140 cases of peanut and tree nut allergies in the children who were born from 1990 to 1994.
The children of moms who ate less than a serving a month of peanuts and tree nuts had a risk of allergies to those foods that was more than three times greater than mothers who ate five or more servings a week, according to the study.
The findings also suggested that women with allergies to nuts should avoid the food. Moms with peanut and tree nut allergies who ate these foods five or more times a week had children with a higher allergy risk, the study showed.
Researchers don't know for sure what causes allergies and it may be a combination of environmental and genetic factors, said Ruchi Gupta, an associate professor of pediatrics at Northwestern University's Feinberg School of Medicine in Chicago who wrote an accompanying editorial. About 1 in 13 children in the U.S. have a food allergy and about 40 percent have a history of severe, potentially life threatening reactions, she said.
"When parents see this huge rise in food allergies, they really want to know how they can help avoid it in their child," Gupta said in a telephone interview. "Eating the foods seems like an easy connection. What I like about this study is they follow these families prospectively and they found no relationship. Avoiding the food does not cause less of an allergy."