Dietary exposures and allergy prevention in high-risk infants

Environmental Interventions for Preventing Atopic Diseases

PURPOSE OF REVIEW

In this review, we detail the exposome (consisting of environmental factors such as diet, microbial colonization, allergens, pollutants, and stressors), mechanistic and clinical research supporting its influence on atopic disease, and potentiation from climate change. We highlight contemporary environmental interventions and available evidence substantiating their roles in atopic disease prevention, from observational cohorts to randomized controlled trials, when available.

RECENT FINDINGS

Early introduction to allergenic foods is an effective primary prevention strategy to reduce food allergy. Diverse dietary intake also appears to be a promising strategy for allergic disease prevention, but additional study is necessary. Air pollution and tobacco smoke are highly associated with allergic disease, among other medical comorbidities, paving the way for campaigns and legislation to reduce these exposures. There is no clear evidence that oral vitamin D supplementation, prebiotic or probiotic supplementation, daily emollient application, and antiviral prophylaxis are effective in preventing atopic disease, but these interventions require further study. While some environmental interventions have a well-defined role in the prevention of atopic disease, additional study of many remaining interventions is necessary to enhance our understanding of their role in disease prevention. Alignment of research findings from randomized controlled trials with public policy is essential to develop meaningful public health outcomes and prevent allergic disease on the population level.

Nurturing Infants to Prevent Atopic Dermatitis and Food Allergies: A Longitudinal Study

BACKGROUND

Atopic dermatitis (AD) at a young age often precedes the development of food allergies. Although AD affects millions of infants worldwide, prenatal and postnatal risk factors, and their association with the development of food allergies later on, are not fully elucidated. This study seeks to investigate AD epidemiology in infancy and its risk factors, examining early-life factors (both prenatal and postnatal) that could contribute to the later development of food allergies.

METHODS

Between January 2019 and December 2019, 501 infants were included in this prospective cohort study. Longitudinal data collection was performed through maternal interviews, the first one conducted within three days after the delivery and the second within 24 to 36 months after the delivery, encompassing variables such as demographics, family history of atopy, maternal smoking, antibiotic use during pregnancy, the mode of delivery, breastfeeding history, food practices, and greenness exposure within 3 days from delivery, while they were still in the hospital.

RESULTS

Maternal smoking during pregnancy (p = 0.001) and an older sibling atopy history (p = 0.03) was significantly linked to AD incidence. Cesarean section delivery (p = 0.04) was associated with a higher risk of food allergies in infants with AD. Having a garden at home correlated with a higher likelihood of AD (p = 0.01), and food elimination without medical guidance (p = 0.02) due to AD correlated with an elevated risk of food allergies.

CONCLUSIONS

Encouraging timely allergenic food introduction while promoting dietary diversity, rich in plant-based foods, maternal smoking cessation, and professional dietary guidance may help minimize AD and food allergy risk. Future studies should address the role of greenness in the development of AD and food allergies.

Updates in Food Allergy Prevention in Children

Although significant evidence exists that feeding early has a role in the prevention of food allergy, this intervention in isolation may not be sufficient. Recent evidence highlights that early introduction of peanut specifically has had no significant impact on the populational prevalence of peanut allergy. Other factors that may contribute to food allergy prevention include regularity of ingestion once an allergen is introduced and consideration to the form in which the allergen is introduced (such as baked versus cooked egg). There are also many practicalities to early feeding and some discrepant viewpoints on these practicalities, which has led to poor implementation of early feeding strategies. In general, preemptive screening before food introduction is not recommended by most international allergy societies. Although there is little guidance to inform early introduction of allergens other than milk, egg, and peanut, the mechanism of sensitization is thought to be similar and there is no harm to early introduction. In terms of frequency and duration of feeding, there is little evidence to inform any concrete recommendations.

Primary Prevention of Allergy - Is It Feasible?

The allergy epidemic has been attributed to environmental influences related to urbanization and the modern lifestyle. In this regard, various theories exploring the role of microbes (hygiene, old friends, microbiota, and biodiversity hypotheses), and the epithelial barrier (epithelial, dual allergen exposure and vitamin D hypotheses) have been proposed. These hypotheses have guided clinical studies that led to the formulation of intervention strategies during the proposed window of opportunity dubbed as the "first thousand days." The most significant intervention is a paradigm shift from allergen avoidance to early introduction of allergenic foods, particularly egg and peanut, around 6 months of age for the prevention of food allergy. This recommendation has been adopted globally and included in allergy prevention guidelines. Other strategies with less robust clinical evidence include: encouraging a healthy balanced diet, rich in fish, during pregnancy; continuing allergenic food intake during pregnancy and lactation; vitamin D supplementation in pregnant women with asthma; discouraging social indications for caesarean section delivery; judicious use of antibiotics in early childhood; daily emollient use from birth in high risk babies; and avoiding cow's milk formula use in the first week of life. However, if early supplementation with cow's milk formula is required, continuing at least 10 mL of formula daily until age 2 months may be considered. Translating these strategies to public health and clinical practice is still a work in progress. Long-term population studies are crucial to assess the feasibility of these measures on allergy prevention.

Prevention of food allergy in infancy: the role of maternal interventions and exposures during pregnancy and lactation

There is increased focus on the role of maternal interventions in the prevention of food allergy in infancy. There is no role for maternal dietary modifications during pregnancy or lactation, such as allergen avoidance, as a means of infant allergy prevention. Although exclusive breastfeeding is the recommended infant nutrition source globally, the effect of breastfeeding on infant allergy prevention remains unclear. There is emerging evidence that irregular cow's milk exposure (ie, infrequent formula supplementation) might increase the risk of cow's milk allergy. Although further studies are required, there is also emerging evidence that maternal peanut ingestion during breastfeeding along with early peanut introduction in infancy might have a preventive role. The effect of maternal dietary supplementation with vitamin D, omega-3, and prebiotics or probiotics remains unclear.