In the JournalsPerspective

Maternal peanut consumption, early introduction protect against allergy

Infants of mothers who consume peanuts while breast-feeding and directly introduce their child to the food by 12 months of age are less likely to be sensitized to peanuts, according to a study published in The Journal of Allergy and Clinical Immunology.

“The prevalence of food allergy has increased in recent decades, particularly in the United Kingdom and other industrialized nations. Approximately 7% of Canadian children have a food allergy, with peanut being among the most common,” Tracy J. Pitt, MD, from the Humber River Hospital, Toronto, Ontario, and colleagues wrote. “There are many theories regarding the cause of food allergy, including breaches in oral tolerance and alternative routes of exposure leading to sensitization… Recent studies suggest that early introduction to peanuts may in fact reduce the likelihood of developing peanut allergy.”

To assess the connection between mothers eating peanuts while breast-feeding, the time in which peanuts are introduced to their child and sensitization at 7 years of age, the researchers conducted secondary analysis of a nested cohort. People studied were included in the 1995 Canadian Asthma Primary Prevention Study intervention study, which encompassed multiple maternal questionnaires while their children were infants. When the children reached 7 years of age, skin prick tests were performed to determine peanut sensitization.

Of the mothers included in the analysis, 58.2% had eaten peanuts while breast-feeding. By the time their infant had reached 12 months of age, 22.5% of mothers had introduced their children to peanuts. At age 7 years, 9.4% of children were determined to be sensitized to peanuts, with the lowest incidence occurring in children who were introduced to peanuts before age 12 months and whose mothers ate peanuts while breast-feeding (1.7%). This combination was observed to be a protective factor against sensitization.

Children were significantly more likely to be sensitized to peanuts if their mothers consumed the food while breast-feeding but delayed introduction until after their infant was older than 12 months (15.1%; P < .05). Additionally, sensitization was also more common in children of mothers who did not eat peanuts while breast-feeding but attempted to introduce the food to their infant by 12 months of age (17.6%). Delayed introduction or maternal avoidance of peanuts while breast-feeding was observed to create an increased risk of sensitization.

“The associations noted in our secondary analysis suggest that maternal peanut consumption while breast-feeding may differentially influence peanut sensitization depending on the timing of direct peanut introduction, and vice versa, although further research is needed to formally test this hypothesis,” Pitt and colleagues wrote. – by Katherine Bortz

Disclosure: Pitt reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.

Infants of mothers who consume peanuts while breast-feeding and directly introduce their child to the food by 12 months of age are less likely to be sensitized to peanuts, according to a study published in The Journal of Allergy and Clinical Immunology.

“The prevalence of food allergy has increased in recent decades, particularly in the United Kingdom and other industrialized nations. Approximately 7% of Canadian children have a food allergy, with peanut being among the most common,” Tracy J. Pitt, MD, from the Humber River Hospital, Toronto, Ontario, and colleagues wrote. “There are many theories regarding the cause of food allergy, including breaches in oral tolerance and alternative routes of exposure leading to sensitization… Recent studies suggest that early introduction to peanuts may in fact reduce the likelihood of developing peanut allergy.”

To assess the connection between mothers eating peanuts while breast-feeding, the time in which peanuts are introduced to their child and sensitization at 7 years of age, the researchers conducted secondary analysis of a nested cohort. People studied were included in the 1995 Canadian Asthma Primary Prevention Study intervention study, which encompassed multiple maternal questionnaires while their children were infants. When the children reached 7 years of age, skin prick tests were performed to determine peanut sensitization.

Of the mothers included in the analysis, 58.2% had eaten peanuts while breast-feeding. By the time their infant had reached 12 months of age, 22.5% of mothers had introduced their children to peanuts. At age 7 years, 9.4% of children were determined to be sensitized to peanuts, with the lowest incidence occurring in children who were introduced to peanuts before age 12 months and whose mothers ate peanuts while breast-feeding (1.7%). This combination was observed to be a protective factor against sensitization.

Children were significantly more likely to be sensitized to peanuts if their mothers consumed the food while breast-feeding but delayed introduction until after their infant was older than 12 months (15.1%; P < .05). Additionally, sensitization was also more common in children of mothers who did not eat peanuts while breast-feeding but attempted to introduce the food to their infant by 12 months of age (17.6%). Delayed introduction or maternal avoidance of peanuts while breast-feeding was observed to create an increased risk of sensitization.

“The associations noted in our secondary analysis suggest that maternal peanut consumption while breast-feeding may differentially influence peanut sensitization depending on the timing of direct peanut introduction, and vice versa, although further research is needed to formally test this hypothesis,” Pitt and colleagues wrote. – by Katherine Bortz

Disclosure: Pitt reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.

    Perspective
    Matthew Greenhawt

    Matthew Greenhawt

    Is early peanut introduction the only factor that promotes immunologic tolerance to peanut?  Surely not. Although the LEAP study showed that early peanut introduction is protective against developing peanut allergy, many leading experts believe that a host of other factors also play a role besides the timing of introduction of potentially allergenic solids.  These include vitamin D, early diversity of the diet, maternal diet during pregnancy, and the microbiome among leading theories.  

    In this month’s Journal of Allergy and Clinical Immunology, secondary analysis of nested data from a large, longitudinal Canadian birth cohort, the Canadian Asthma and Primary Prevention Study (CAPPS), took a look at this very issue.  Infants were enrolled starting in 1995, predating the 2000 AAP recommendations for delayed peanut introduction in at-risk infants (with a parental history of allergic disease).  The cohort had nested data from caregiver questionnaires related to breast-feeding, infant feeding, and allergic outcomes during the study, as well as had allergy skin testing to foods (but not actual food allergy) as part of the final outcome assessment.  Food-related outcomes were not a primary aim of this study, so complete data were available on 342/545 of the originally enrolled children.  

    Investigators noted that only 23% of caregivers introduced peanut in the first year of life — with the rest of the cohort introducing peanut equally in the second year and the third year of life.  Nearly 58% of the mothers reported consuming peanut while breast-feeding (which per the year 2000 AAP guidelines was also not recommended). At the end of the study, when the children were aged 7 years, only 9.4% were sensitized to peanut (eg, have positive skin testing to peanut).  Athough the highest rates of peanut- sensitized children were from mothers consuming peanut while breast-feeding or who introduced peanut in the first year of life, the lowest incidence of sensitization was in the children where the mom both ate peanut while breast-feeding and introduced peanut in the first year of life.  It was unclear how much overlap there was between these two factors.

    Although this finding is interesting, there are many problems with the study. First, this does not imply allergy, just peanut sensitization.  To be allergic, one needs both sensitization to the food and IgE-mediated symptoms upon ingestion of that food. A positive test alone does not mean allergy.  Second, there is considerable recall bias. There was poor reporting of the frequency/amounts of exposure of the peanut consumption while both breast-feeding and in the first year of life, as well as how precise the degree of overlap between maternal exposure and peanut introduction in the child may have been. Thus, these findings highlight a potential association of interest but do not implicate causality, so enthusiasm must be tempered.  It is important to note that in the U.S., Canada, the U.K., Australia and New Zealand, peanut is recommended to be given in the first year of life, and that no guidelines recommend any allergen avoidance while pregnant or while breast-feeding. Therefore, there would not be any implications to change current clinical practices based on this study.

    I do caution that this association may be very difficult to prove definitively, even with a better designed study. Remember, the LEAP study looked only at timing of peanut introduction as a randomized intervention, and did not randomize any other outcome. Therefore, even similar nested data from the LEAP study (with a definitive outcome of who was peanut allergic or not) could do no more than reaffirm the potential association seen in the CAAPS data but could not show causality.  The issue is with maternal allergen transfer. Although many believe that allergens can pass through breast milk to the infant, this has not actually been conclusively demonstrated to happen consistently in previous studies. Therefore, considerable work would be needed first to definitively prove the hypothesis of passive allergen transfer through breast milk, that this can induce allergy in the infant, and then design a study that could control the amount/frequency the mother consumes as a variable to interact with an exact timing of overlap with active peanut introduction in the infant. This would be exceptionally difficult to do.

    Nonetheless, the take-home message from this study is to inform that although the early introduction of peanut may be a key factor in preventing peanut allergy, it may not be the only such factor.  

    • Matthew Greenhawt, MD, MSc
    • Infectious Diseases in Children Editorial Board member Chair, American College of Allergy, Asthma and Immunology Food Allergy Committee Associate professor of pediatrics Director, food challenge and research unit section of allergy and immunology Children’s Hospital Colorado University of Colorado School of Medicine

    Disclosures: Greenhawt reports no relevant financial disclosures.