Clinician Roundtable: Can Dietary Interventions Prevent Asthma, Atopy in Children?

In April 2019, the American Academy of Pediatrics (AAP) published an update to their 2008 clinical report providing guidance on the prevention of atopic disease through maternal and early infant nutritional interventions.¹ While the authors noted that current data are still inadequate to inform definitive conclusions on many aspects related to atopy prevention through dietary strategies, recent evidence has led to the revision of certain recommendations.

“Although atopic diseases have a clear genetic basis, environmental factors, including early infant nutrition, have an important influence on their development,” they wrote. “Thus, for pediatric health care providers, there is great interest in early nutritional strategies that may ameliorate or prevent this disease.”

Pulmonology Advisor interviewed a range of experts to explore the updated guidelines as they pertain to asthma and food allergy:

Jonathan Spergel, MD, PhD, chief of the allergy section at Children’s Hospital of Philadelphia in Pennsylvania

Gigi Chawla, MD, MHA, pediatrician, hospitalist, and chief of general pediatrics at Children’s Minnesota in Minneapolis

Jonathan Tam, MD, medical director of the Gores Family Allergy Center at Children’s Hospital Los Angeles and assistant professor of clinical pediatrics at the Keck School of Medicine of the University of Southern California

Ankoor Shah, MD, MBA, MPH, pediatrician and medical director of the IMPACT DC Asthma Clinic at Children’s National Health System and assistant professor of pediatrics at the George Washington University School of Medicine & Health Sciences in Washington, DC

Adora A. Lin, MD, PhD, attending physician in the department of allergy and immunology at Children’s National Health System, assistant professor of pediatrics at George Washington University School of Medicine and Health Sciences, and researcher conducting ongoing research on food allergies in Washington, DC

Editor’s Note: These interviews have been edited for length and clarity.

Pulmonology Advisor: What is known thus far about associations between maternal and early infant diet and atopic disease, specifically, asthma and food allergy?

Dr Spergel: Maternal diet and early infant diet have no effect on asthma or atopic dermatitis after the age of 2 years.¹ Breastfeeding is associated with a temporary decrease in atopic dermatitis or eczema in young infants. However, we know that asthma is more common in children with food allergy, and the early introduction of foods may prevent food allergy.¹

Dr Chawla: Right now, evidence supports that there is no specific dietary restriction preventing atopy or asthma. Although there has been ample study in this area, a maternal diet that is most consistent with a Mediterranean diet has been associated with lower risk for allergic disease.² Higher-risk disease was related to diets including vegetable oils, nuts, and fast food.^1,2

Breastfeeding through the first 3 to4 months has shown decreases in atopy through 2 years of age and a decrease in wheezing and asthma after 5 years of age.¹

Dr Tam: The timing of food introduction for the prevention of food allergy has recently been of significant interest. Most trials have focused on the introduction of one food only, usually egg or peanut.

Based on the results of a single landmark study — the 2015 Learning Early About Peanut Allergy (LEAP; ClinicalTrials.gov Identifier: NCT00329784) study³ — the National Institute of Allergy and Infectious Diseases (NIAID) published an addendum to the Guidelines for the Prevention of Peanut Allergy in the United States.⁴ This was the first randomized trial to study early allergen introduction as a preventive strategy. The results showed that early introduction of peanut-containing foods to infants at high risk for peanut allergy, such as those with severe eczema or egg allergy, was not only safe but also led to an 86% relative reduction in the subsequent development of peanut allergy.³

It is unclear whether early introduction of other foods would have the same effect. A recent meta-analysis investigating the timing of allergenic food introduction to the infant diet found moderate evidence that egg introduction at 4 to 6 months was associated with reduced egg allergy, and that peanut introduction at 4 to 11 months was associated with reduced peanut allergy.⁵

As a result of these addendum guidelines, we have food-challenged infants with “mildly” positive allergy tests to peanut who have successfully gone on to eat peanuts. In the past, these children may have just been labeled peanut allergic.

There is currently no evidence that early introduction of cow’s milk, fish, sesame, and wheat protects against the development of food allergy; conversely, it is important to note that the addition of common food allergens (eg, peanut, egg, fish, sesame, milk) to the infant diet has no adverse nutritional or growth effects and does not increase rates of food allergy.¹

The effect of breastfeeding on wheezing and the development of asthma is in some ways controversial, as some studies report evidence toward beneficial effects while others have found no association or even increased risk.¹ Several systematic reviews have been conducted to synthesize the existing evidence on this topic, but when they combined studies, conclusions have differed. There are several issues that have led to this inconsistency, including variations in study populations, different definitions of breastfeeding and asthma, and cultural differences surrounding breastfeeding practices.  Reverse causality is another potential source of bias in observational research.¹

Dr Shah: Currently there is no evidence that supports a soon-to-be mother changing her diet to remove things like milk or eggs during the prenatal period to improve the likelihood of her child not having eczema, food allergy, or asthma.

There is a study that might show an association with a maternal diet high in fruits, vegetables, fish, and vitamin D (or a Mediterranean diet) with lower chances of the child developing allergies or asthma.²

In terms of breastfeeding, there is an association between breastfeeding exclusively for at least 4 months and a reduction in the development of asthma, with longer breastfeeding being more protective.¹

Dr Lin: The LEAP-On study (ClinicalTrials.gov Identifier: NCT01366846) showed that the  protective effect of early peanut introduction persists even after a period of peanut avoidance, suggesting that true tolerance was achieved.⁶ These studies led to the 2017 addendum guidelines from NIAID regarding infant peanut introduction.⁴

Meanwhile, the EAT study (ISRCTN Registry Number: 14254740) looked at early food introduction in non-high-risk, breastfed babies.⁷ The results from that study suggest that for breastfed infants, egg and peanut allergy could be prevented by a sufficient amount and duration of early exposure.

So far, the suggestion from these studies is that earlier introduction of foods, especially with regard to peanut and high-risk infants, can decrease the risk for food allergy developing. But we are far from making that a blanket statement for all foods and all infants.

Pulmonology Advisor: What are your thoughts about the updated AAP report, and how might it be helpful to clinicians?

Dr Spergel: The AAP report is consistent with both the National Institutes of Health and AAAAI [American Academy of Asthma, Allergy & Immunology] reports that early introduction is helpful. In fact, there are multiple studies that favor early introduction and almost none that recommend delayed introduction. The AAP guidelines reinforce the National Institutes of Health and AAAAI/ACAAI [American College of Asthma, Allergy, and Immunology] guidelines that recommend peanut around 4 to 6 months of age and other foods when they can be tolerated.⁴

Dr Chawla: The updated AAP report does help us better understand and translate the LEAP study for potential prevention of peanut allergy.³ In that study, and through the AAP report, best practice medicine now allows for earlier introduction of peanut in a dietary-appropriate manner in younger infants to prevent peanut allergy. Although there is not specific consensus on the introduction of other allergenic foods such as egg or fish, there is also no evidence that delaying these foods creates benefit.¹

Dr Tam: The updated AAP report on the Effects of Early Nutritional Interventions on the Development of Atopic Disease in Infants and Children has a few key changes from the 2008 report.¹ The largest change highlights the NIAID’s addendum Guidelines for the Prevention of Peanut Allergy in the United States.⁴ It stresses that the timing of introduction of complementary foods does not have to be feared and has been shown to be beneficial for egg and peanut.