Inverse associations between food diversity in the second year of life and allergic diseases

Emerging concepts in introducing foods for food allergy prevention

PURPOSE OF REVIEW

This review focuses on the latest information regarding the role of complementary feeding practices and food allergen introduction in the prevention of food allergies.

RECENT FINDINGS

Early introduction of food allergens for food allergy prevention is recommended by food allergy prevention guidelines and is supported by the latest randomized controlled trials. Diet diversity is recommended, supported by the latest studies from Asia. A European study indicated that diet diversity after the first year of life may still be important for food allergy prevention. The latest systematic reviews indicate there may be an association between ultra-processed food intake and food allergy development. Plant based foods and fiber play an important role in modulating the gut microbiome which has been associated with reduced food allergy outcomes. However, increased intake of food allergens within a diverse diet raises questions about excessive calorie and protein intake but can be managed by focusing on infant satiety cues.

SUMMARY

The latest studies clearly indicate and further supports that introduction of food allergies should not be delayed once complementary feeding is commenced. A diverse diet is recommended to further support the prevention of food allergies.

Dietary Intake, Diet Diversity, and Weight Status of Children With Food Allergy

BACKGROUND

Adoption of allergen avoidance diets may increase the risk of nutritional deficiencies and affect growth in children with food allergy (FA). How these dietary restrictions have an impact on diet diversity, a health-promoting eating behavior, remains unclear.

OBJECTIVE

To evaluate diet diversity, dietary intake, and weight status of children with FA.

DESIGN

Observational study.

PARTICIPANTS/SETTING

One hundred children with immunoglobulin E (IgE)-mediated milk, egg, or nut FA or multiple FAs and 60 children with perennial respiratory allergies (RA) matched as controls, aged 3 to 18 years, were consecutively recruited into the study.

MAIN OUTCOME MEASURES

Dietary intake and diet diversity (number of different foods consumed/day) were assessed through 4 24-hour recalls. Weight status (underweight, healthy weight, overweight, or obesity) was also evaluated.

STATISTICAL ANALYSES PERFORMED

Chi-squared test and 2-sample independent t test were used to test differences between groups. Adjustment for sex, age, and energy intake was made using linear regression.

RESULTS

The percentage of underweight was higher in children with FA (19.6%) compared with children in the control group (5.1%). Children with FA compared with children in the control group consumed more servings of meat (1.7, 95% CI, 1.6, 1.9 vs. 1.5, 95% CI, 1.3, 1.7 servings/day [Padj = 0.031]). No difference was observed in the diet diversity between the 2 groups (11-12 different foods/day). Within the FA group, children with allergy to milk proteins had lower energy intake from protein, lower intake of calcium, lower consumption of commercially prepared sweets, and higher consumption of eggs, compared with children with nut or egg allergy, but no difference in diet diversity was observed.

CONCLUSIONS

Diet diversity did not differ between children with FA and children with no FA, despite some differences in the intake from specific food groups. However, the higher percentage of underweight in children with FA suggests the need for targeted nutrition intervention as early as possible after FA diagnosis.

Associations between diet diversity during infancy and atopic disease in later life: Systematic review

Background

The incidence of allergic disease remains high, and many studies have focused on the association between food diversity in infancy and allergic disease later in life, but their conclusions are still controversial.

Objective

We aimed to synthesize the literature on the association between childhood diet diversity and atopic disease.

Methods

We searched the PubMed, Cochrane Library, Embase, Scopus, VPCS, and Wanfang databases for studies about food diversity and atopic disease. Seventeen high-quality studies, 14 cohort studies, and 1 case-control study were included from 5244 studies with sample sizes ranging from 100 to 5225.

Results

All high-quality cohort studies showed that increasing food diversity in infancy can effectively prevent the occurrence of food allergies (5/5). Moderate evidence showed that increased food diversity reduced the risk of asthma (4/6), food sensitization (3/5), and atopic dermatitis (3/5). However, its effect on eczema (5), allergic rhinitis (4), and other diseases remains controversial.

Conclusions

Increasing food diversity during infancy is a potential method for preventing food allergy, asthma, atopic dermatitis, and food sensitization later in life. There is little or no comparative evidence about the protective effect of food diversity on other atopic diseases.

Pre-asthma: a useful concept for prevention and disease-modification? A EUFOREA paper. Part 1-allergic asthma

Asthma, which affects some 300 million people worldwide and caused 455,000 deaths in 2019, is a significant burden to suffers and to society. It is the most common chronic disease in children and represents one of the major causes for years lived with disability. Significant efforts are made by organizations such as WHO in improving the diagnosis, treatment and monitoring of asthma. However asthma prevention has been less studied. Currently there is a concept of pre- diabetes which allows a reduction in full blown diabetes if diet and exercise are undertaken. Similar predictive states are found in Alzheimer's and Parkinson's diseases. In this paper we explore the possibilities for asthma prevention, both at population level and also investigate the possibility of defining a state of pre-asthma, in which intensive treatment could reduce progression to asthma. Since asthma is a heterogeneous condition, this paper is concerned with allergic asthma. A subsequent one will deal with late onset eosinophilic asthma.

Immunonutrition: Diet Diversity, Gut Microbiome and Prevention of Allergic Diseases

Allergic diseases are increasing both in morbidity and mortality. Genetic, environmental, and dietary factors may all be involved in this increase. Nutrition during pregnancy, breastfeeding, and early life may play a particularly important role in preventing allergic diseases. Based on current systematic reviews, the intake of specific nutrients has failed to prevent allergic disease. Prevention strategies have shifted their focus to the overall diet which can be described using diet diversity. Infant and maternal diet diversity in pregnancy has been associated with reduced allergy outcomes in childhood. Overall, diet also seems to have a marked effect on the microbiome compared to single foods. Factors that may negate the allergy-preventative effect of overall diet diversity include the addition of emulsifiers, advanced glycation end-product content, and overuse of commercial baby foods. There is a need to perform randomized controlled trials using overall dietary intake to support international food allergy guidelines. These studies should ideally be conducted by multi-professional teams.

Food allergy prevention: Where are we in 2023?

Food allergy prevention involves recommendations to the maternal diet during pregnancy and breast feeding, early life feeding and introduction of solid foods. Pregnant and breastfeeding women are not recommended to exclude any food allergens from their diet, but data are lacking to support active consumption of food allergens for prevention of food allergy. Breastfeeding is recommended for the many health benefits to the mother and child but has not shown any association with reduction in childhood food allergies. There is currently no recommendation regarding the use of any infant formula for allergy prevention, including the use of partially or extensively hydrolyzed formulas. Once the introduction of solid food commences, based on randomized controlled trials, it is advised to actively introduce peanuts and egg early into the infant diet and continue with consumption of these. Although there are limited data with respect to other major food allergens and whether early introduction may prevent allergy development, there is no need to delay the introduction of these allergens into the infant diet. Interpreting food allergen consumption in the context of cultural food practices has not been studied, but it makes sense to introduce the infant to family foods by 1 year of age. Consumption of foods typical of the Western diet and foods high in advanced glycation end products may be associated with an increase in food allergies. Similarly, intake of micronutrients, such as vitamin D and omega-3 fatty acids in both the maternal and infant diet, needs further clarification in the context of food allergy prevention.

The clinical and immunological basis of early food introduction in food allergy prevention

IgE-mediated food allergy has an estimated prevalence of 6%-10% in developed countries. Allergen avoidance has long been the main focus in the prevention of food allergy and late solid food introduction after 6-12 months of age was recommended in high-risk infants. However, the rising prevalence of food allergy despite delayed exposure to allergens and the observations that IgE-mediated sensitization to food products could even occur before the introduction of solid foods resulted in a shift towards early solid food introduction as an attempt to prevent IgE-mediated food allergy. Since then, many trials focused on the clinical outcome of early allergen introduction and overall seem to point to a protective effect on the development of IgE-mediated food allergies. For non-IgE-mediated diseases of food allergy, evidence of early food introduction seems less clear. Moreover, data on the underlying immunological processes in early food introduction is lacking. The goal of this review is to summarize the available data of immunological changes in early food introduction to prevent IgE and non-IgE mediated food allergy.

Understanding the development of Th2 cell-driven allergic airway disease in early life

Allergic diseases, including atopic dermatitis, allergic rhinitis, asthma, and food allergy, are caused by abnormal responses to relatively harmless foreign proteins called allergens found in pollen, fungal spores, house dust mites (HDM), animal dander, or certain foods. In particular, the activation of allergen-specific helper T cells towards a type 2 (Th2) phenotype during the first encounters with the allergen, also known as the sensitization phase, is the leading cause of the subsequent development of allergic disease. Infants and children are especially prone to developing Th2 cell responses after initial contact with allergens. But in addition, the rates of allergic sensitization and the development of allergic diseases among children are increasing in the industrialized world and have been associated with living in urban settings. Particularly for respiratory allergies, greater susceptibility to developing allergic Th2 cell responses has been shown in children living in urban environments containing low levels of microbial contaminants, principally bacterial endotoxins [lipopolysaccharide (LPS)], in the causative aeroallergens. This review highlights the current understanding of the factors that balance Th2 cell immunity to environmental allergens, with a particular focus on the determinants that program conventional dendritic cells (cDCs) toward or away from a Th2 stimulatory function. In this context, it discusses transcription factor-guided functional specialization of type-2 cDCs (cDC2s) and how the integration of signals derived from the environment drives this process. In addition, it analyzes observational and mechanistic studies supporting an essential role for innate sensing of microbial-derived products contained in aeroallergens in modulating allergic Th2 cell immune responses. Finally, this review examines whether hyporesponsiveness to microbial stimulation, particularly to LPS, is a risk factor for the induction of Th2 cell responses and allergic sensitization during infancy and early childhood and the potential factors that may affect early-age response to LPS and other environmental microbial components.

Environmental influences on childhood allergies and asthma - The Farm effect

Asthma and allergies are major health problems and exert an enormous socioeconomic burden. Besides genetic predisposition, environmental factors play a crucial role in the development of these diseases in childhood. Multiple worldwide epidemiological studies have shown that children growing up on farms are immune to allergic diseases and asthma. Farm-related exposures shape children's immune homeostasis, via mediators such as N-glycolylneuraminic acid or arabinogalactan, or by diverse environmental microbes. Moreover, nutritional factors, such as breastfeeding or farm milk and food diversity, inducing short-chain fatty acids-producing bacteria in the intestine, contribute to farm-related effects. All farm-related exposures induce an anti-inflammatory response of the innate immunity and increase the differentiation of regulatory T cells and T helper cell type 1. A better understanding of the components of the farm environment, that are protective to the development of allergy and asthma, and their underlying mechanisms, will help to develop new strategies for the prevention of allergy and asthma.