Should You Advise Your Patients to Eat Peanuts During Pregnancy?
Abstract & Commentary
By Rebecca H. Allen, MD, MPH
Assistant Professor, Department of Obstetrics and Gynecology, Warren Alpert Medical School of Brown University, Women and Infants Hospital, Providence, RI
Dr. Allen reports no financial relationships relevant to this field of study.
Synopsis: In this study, women without allergies who consumed peanuts or tree nuts five times or more per month around the time of pregnancy compared to less than one time per month had reduced odds of having children with peanut or tree nut allergies.
Source: Frazier AL, et al. Prospective study of peripregnancy consumption of peanuts or tree nuts by mothers and the risk of peanut or tree nut allergy in their offspring. JAMA Pediatrics Published online December 23, 2013. [Epub ahead of print.]
This is a nested case-control study using two large national prospective cohort studies — the Nurses' Health Study II (NHSII) and the Growing Up Today Study 2 (GUTS2), which involved offspring of the participants of NHSII. Children in the GUTS2 study were born between January 1, 1990 and December 31, 1994. In 2009, to identify children with food allergies, a questionnaire was sent to the mother of every child in the GUTS2 cohort (n = 10,907). The children themselves had already reported on whether or not they had a food allergy in a 2006 GUTS2 questionnaire. The investigators reconciled answers to these two questionnaires and identified cases of allergy to peanut or tree nuts (P/TN). The cases were then divided into seven levels of confirmation, ranging from likely to possible based on review of available medical record information. The mothers had previously reported their diet on the 1991 and 1995 NHSII questionnaires, and the authors selected the questionnaire closest to the birthday of each child to determine maternal peanut intake. Investigators estimated that 45% of the food questionnaires were answered when the mother would have been pregnant with the child and 76% were within 1 year of the pregnancy.
After exclusions for missing data, the authors identified 8205 children (75% of the GUTS2 cohort) with 140 cases of P/TN allergy. The majority (> 95%) of the NHSII and GUTS2 sample was white, and 2% of the mothers reported a nut allergy. Women with the highest consumption of P/TN in their peripregnancy diet were more likely to introduce P/TN into their child's diet at a younger age (< 2 years old). In multivariable analysis controlling for maternal age, maternal history of non-nut allergy, maternal allergic rhinitis, eczema, asthma, and season at child's birth, the odds of having a child with P/TN allergy among mothers without a P/TN allergy themselves who had the highest consumption peripregnancy (≥ 5 servings/week) was reduced (odds ratio [OR], 0.31; 95% confidence interval [CI], 0.13-0.75). Interestingly, among mothers with a P/TN allergy themselves, the association was in the opposite direction, although not statistically significant (OR, 2.62; 95% CI, 0.74-9.27).
COMMENTARY
The incidence of peanut allergy has increased markedly in the United States from 0.4% in 1997 to 1.4% in 2010.1 This should come as no surprise to anyone who has children in the daycare or school setting, where peanuts are often banned. Peanut and tree nut allergy frequently occur together and 80-90% of cases occurring in childhood persist into adulthood. Since the majority of the IgE-mediated reactions occur during the child's first known exposure, the theory is that the child was exposed previously either in utero or through other unrecognized environmental or diet exposures. For many years, women have been advised to avoid giving their children peanuts in the first 3 years of life. In addition, some experts advised avoiding peanuts during pregnancy and lactation. These guidelines were then changed when little evidence was found to support them.2 In essence, a number of prospective studies had shown that maternal consumption of peanuts during pregnancy and lactation had no effect on subsequent development of P/TN allergy.3
This study aimed to clarify the association with peripregnancy consumption of P/TN by mothers and the subsequent development of P/TN allergy or not in their children. This is the first study in humans that showed ingestion of P/TN during pregnancy may actually protect against allergy in the offspring, at least among women without any allergy themselves. The investigators worked diligently to confirm cases of P/TN allergy by reviewing medical records, allergy skin test results, and specific IgE data. At the same time, the data on P/TN consumption were limited by the fact that the questionnaires were not specific to the actual dates of pregnancy. Therefore, the authors are assuming that the mother's eating habits were stable in the peripregnancy time period. To respond to this, the authors compared P/TN consumption during a pregnancy to that same individual's diet when not pregnant and found that 72% of women reported similar intake. Nevertheless, the quality of the data is not the same as a true prospective study where diet is diligently recorded during pregnancy. In fact, I find it questionable that the authors use the word "prospective" in their title. The quality of the data is also dependent on how accurately women filled out the questionnaires regarding their diet. In addition, no data were collected on exclusive breastfeeding rates or duration, which may or may not influence the development of allergies.2
The bottom line is that it is difficult to definitively prove causation with observational studies, especially in this realm where there are multiple confounding factors. The pediatric guidance currently states that there is not enough evidence that maternal dietary restrictions during pregnancy play any role in the prevention of atopic disease in infants.2 Similarly, there is not enough evidence to say that consumption of dietary food allergens in pregnancy will reduce the chance of allergy development to those allergens in the infant. So, if your patient asks you about eating peanuts during pregnancy, I would say there is no good evidence it will cause or prevent a peanut allergy in her child; we just don't have enough information. So, pregnant patients can indulge any peanut butter cravings!
References
- Sicherer SH, et al. US prevalence of self-reported peanut, tree nut, and sesame allergy: 11-year follow up. J Allergy Clin Immunol 2010;125:1322-1326.
- Greer FR, et al. Effects of early nutritional interventions on the development of atopic disease in infants and children: The role of maternal dietary restriction, breastfeeding, timing of introduction of complementary foods, and hydrolyzed formulas. Pediatrics 2008;121:183-191.
- Thompson RL, et al. Peanut sensitization and allergy: Influence of early life exposure to peanuts. Br J Nutr 2010;103:1278-1286.
