Retinol concentrations after birth are inversely associated with atopic manifestations in children and young adults

Malnutrition and Allergies: Tipping the Immune Balance towards Health

Malnutrition, which includes macro- and micronutrient deficiencies, is common in individuals with allergic dermatitis, food allergies, rhinitis, and asthma. Prolonged deficiencies of proteins, minerals, and vitamins promote Th2 inflammation, setting the stage for allergic sensitization. Consequently, malnutrition, which includes micronutrient deficiencies, fosters the development of allergies, while an adequate supply of micronutrients promotes immune cells with regulatory and tolerogenic phenotypes. As protein and micronutrient deficiencies mimic an infection, the body's innate response limits access to these nutrients by reducing their dietary absorption. This review highlights our current understanding of the physiological functions of allergenic proteins, iron, and vitamin A, particularly regarding their reduced bioavailability under inflamed conditions, necessitating different dietary approaches to improve their absorption. Additionally, the role of most allergens as nutrient binders and their involvement in nutritional immunity will be briefly summarized. Their ability to bind nutrients and their close association with immune cells can trigger exaggerated immune responses and allergies in individuals with deficiencies. However, in nutrient-rich conditions, these allergens can also provide nutrients to immune cells and promote health.

Specific and nonspecific nutritional interventions enhance the development of oral tolerance in food allergy

The goal of food allergy (FA) prevention and treatment is to induce oral tolerance (OT). Appropriate nutritional interventions are essential to induce OT to food allergens. This review introduces the mechanism of OT and the importance of early nutritional interventions, and then firstly summarizes specific nutritional factors to induce the development of OT of FA, including proteins, vitamins, fatty acids, saccharides and probiotics. The regulatory mechanism mainly induces the development of tolerance by increasing local or systemic protective regulatory T cells (Tregs) to suppress FA, while the gut microbiota may also be changed to maintain intestinal homeostasis. For allergens-specific OT, the disruption to the structure of proteins and epitopes is critical for the induction of tolerance by hydrolyzed and heated proteins. Vitamins (vitamin A, D), fatty acids, saccharides and probiotics as allergens nonspecific OT also induce the development of OT through immunomodulatory effects. This review contributes to our understanding of OT in FA through nutritional interventions. Nutritional interventions play an important role in the induction of OT, and offer promising approaches to reduce allergy risk and alleviate FA. Moreover, due to the importance and diversity of nutrition, it must be the future trend of induction of OT in FA.

Lack of iron, zinc, and vitamins as a contributor to the etiology of atopic diseases

Micronutritional deficiencies are common in atopic children suffering from atopic dermatitis, food allergy, rhinitis, and asthma. A lack of iron, in particular, may impact immune activation with prolonged deficiencies of iron, zinc, vitamin A, and vitamin D associated with a Th2 signature, maturation of macrophages and dendritic cells (DCs), and the generation of IgE antibodies. In contrast, the sufficiency of these micronutrients establishes immune resilience, promotion of regulatory cells, and tolerance induction. As micronutritional deficiencies mimic an infection, the body's innate response is to limit access to these nutrients and also impede their dietary uptake. Here, we summarize our current understanding of the physiological function of iron, zinc, and vitamins A and D in relation to immune cells and the clinical consequences of deficiencies in these important nutrients, especially in the perinatal period. Improved dietary uptake of iron is achieved by vitamin C, vitamin A, and whey compounds, whereas zinc bioavailability improves through citrates and proteins. The addition of oil is essential for the dietary uptake of beta-carotene and vitamin D. As for vitamin D, the major source comes via sun exposure and only a small amount is consumed via diet, which should be factored into clinical nutritional studies. We summarize the prevalence of micronutritional deficiencies of iron, zinc, and vitamins in the pediatric population as well as nutritional intervention studies on atopic diseases with whole food, food components, and micronutrients. Dietary uptake via the lymphatic route seems promising and is associated with a lower atopy risk and symptom amelioration. This review provides useful information for clinical studies and concludes/emphasizes that a healthy, varied diet containing dairy products, fish, nuts, fruits, and vegetables as well as supplementing foods or supplementation with micronutrients as needed is essential to combat the atopic march.

Allergy prevention by breastfeeding: possible mechanisms and evidence from human cohorts

PURPOSE OF REVIEW

Allergy is a modern disease which does not seem to benefit from breast milk preventive effects. We propose that maternal milk composition has not adapted to the needs of allergy prevention because of the recent and rapid increase of allergy. Modulation of breast milk composition may be the best strategy to counteract allergy development. We will review recent advances in understanding of allergy physiopathology and how breast milk factors may be specifically appropriate to interfere with allergy development in early life.

RECENT FINDINGS

There is strong evidence both from rodent and human studies that breast milk factors may impact on parameters which are now recognized to be essential for allergy physiopathology: infant gut barrier function, microbiota metabolites production, and oral tolerance induction. Data from human cohorts support the possibility to modify breast milk composition by selected interventions and to impact health outcomes in offspring.

SUMMARY

Nutritional intervention in lactating mothers should endow breast milk with the capacity to combat allergy epidemics in addition to infectious disease.

Modulación de la respuesta alérgica por los carotenoides de la dieta

<p>Los carotenoides son pigmentos isoprenoides que están presentes de manera natural y en altas concentraciones en la mayoría de alimentos vegetales —entre ellos, aguacate, papaya, tomate y zanahoria—, pero también encontrados como aditivos y colorantes en diversos productos cárnicos, aceites vegetales, salsas, aderezos, harinas, entre otros. En los últimos años, algunos estudios han descrito que los carotenoides de la dieta participan en varios procesos fisiopatológicos, incluyendo la respuesta inmune de tipo alérgico. Las tasas de prevalencia para este tipo de enfermedades han incrementado de manera alarmante durante las últimas cinco décadas en todo el mundo, a la vez que varios factores e hipótesis se han planteado tratando de explicar este fenómeno: uno de ellos es la hipótesis de la dieta, la cual plantea que la composición de varios micro y macronutrientes de la alimentación, así como los cambios en los patrones dietarios, influirían en tal problemática. Evidencia epidemiológica y básica experimental emergente señala que los carotenoides de la dieta participan en la regulación de la inflamación alérgica, y por ello se postulan como coadyuvantes en la terapia de tales padecimientos. En el presente artículo se revisará el estado del arte en relación a los efectos de los carotenoides de la dieta sobre la patología alérgica.</p>

Oral tolerance is inefficient in neonatal mice due to a physiological vitamin A deficiency

Increased risk of allergy during early life indicates deficient immune regulation in this period of life. To date, the cause for inefficient neonatal immune regulation has never been elucidated. We aimed to define the ontogeny of oral tolerance and to identify necessary conditions specific for this stage of life. Ovalbumin (OVA) was administered orally to mice through breast milk and efficiency of systemic tolerance to OVA was assessed in adulthood using a model of allergic airway inflammation. Oral tolerance induction was fully efficient starting third week of life. Inefficiency in neonates was a consequence of abnormal antigen transfer across the gut barrier and retinaldehyde dehydrogenase expression by mesenteric lymph node CD103(+) neonatal dendritic cells, resulting in inefficient T-cell activation. Neonates' serum retinol levels were three times lower than in adult mice, and vitamin A supplementation was sufficient to rescue neonatal defects and allow tolerance induction from birth. The establishment of oral tolerance required the differentiation of Th1 lymphocytes in both vitamin A-supplemented neonates and 3-week-old unsupplemented mice. This knowledge should guide the design of interventions for allergy prevention that are adapted to the neonatal stage of life such as vitamin A supplementation.

Breast milk and its impact on maturation of the neonatal immune system

PURPOSE OF REVIEW

This article aims to review the evidence that breast milk can actively shape neonate gut immune system development toward a mature immune system capable of responding appropriately to encountered antigens.

RECENT FINDINGS

Recent findings in the adult have demonstrated the critical role of the interaction between diet, gut microbiota, gut epithelial cells and gut-associated lymphoid tissue in the development of immune responses. Here, we will review what is known in this field in the neonate, compare these data to those obtained in the adult and review how milk factors impact gut immune function in the short and long term.

SUMMARY

We propose that the neonate immune system and maternal milk represent an entity necessary to ensure not only appropriate function in early life but also long term immune homeostasis.

Allergen skin prick testing in early childhood: reproducibility and prediction of allergic symptoms into early adulthood

OBJECTIVE

To assess the predictive value of skin prick testing in early childhood on subsequent allergic symptoms up to adult age.

STUDY DESIGN

A cohort of 200 unselected healthy newborns was prospectively followed from birth to 20 years of age. Of them, 163 (82%) were reassessed at age 5 years, 150 (76%) at age 11 years, and 164 (83%) at age 20 years with a skin prick test that included 11 common allergens. On the basis of clinical examination and structured interview, the occurrence of atopic dermatitis, allergic rhinoconjunctivitis, recurrent wheezing, and symptoms of food hypersensitivity were recorded at each of the follow-up visits.

RESULTS

The reproducibility of skin prick test positivity at age 5 years was 100% at ages 11 and 20 years, ie, none of the skin prick-positive subjects turned negative during the follow-up. Gaining of new sensitizations to aeroallergens was common. Skin prick test positivity at age 5 years predicted allergic symptoms at ages 11 (sensitivity 28%, specificity 94%) and 20 years (sensitivity 23%, specificity 91%) but not atopic dermatitis.

CONCLUSIONS

Skin prick test positivity at age 5 years strongly predicts later skin prick test positivity and is associated with respiratory symptoms, ie, allergic rhinoconjunctivitis and recurrent wheezing, at ages 11 and 20 years. However, skin prick test negativity at age 5 years does not exclude sensitization and allergic symptoms at a later age.

Confounding and effect modification in studies of diet and childhood asthma and allergies

OBJECTIVE

To propose a comprehensive set of confounders and effect modifiers that should be considered in epidemiologic investigations.

METHODS

Two reviewers independently critiqued studies included in a recent systematic review and extracted data on the confounders and effect modifiers that were considered and the approaches used to justify inclusion.

RESULTS

Of the 62 studies reviewed, 20 were cohort, 16 case-control, 25 cross-sectional studies, and one ecologic study. All cohort, cross-sectional, and ecologic studies had some adjustment for confounding or consideration of effect modification, but this was only the case for 7/16 (44%) case-control studies. Of the 53 studies that considered confounding or effect modification, 39/53 (74%) gave no justification for the inclusion of the variables considered. Studies that justified the inclusion of the variables did so based on empirical evidence (n = 10), conceptual justification (n = 7), or a combination of the two (n = 3). Confounding was handled mainly by using regression modeling, but some case-control studies utilized matching and anova. Ten studies handled effect modification by stratification, eight tested for interaction, and five used both strategies.

CONCLUSIONS

We have found substantial shortcomings in the handling of confounding and effect modification in studies of diet and development of childhood asthma/allergies. Selection of variables should be based on conceptual considerations and empirical evidence. Using this approach, we have proposed a comprehensive set of confounders and effect modifiers that need to be considered in future studies.

Nutrients and foods for the primary prevention of asthma and allergy: systematic review and meta-analysis

BACKGROUND

Epidemiologic studies suggest that deficiencies of the nutrients selenium; zinc; vitamins A, C, D, and E; and low fruit and vegetable intake may be associated with the development of asthma and allergic disorders.

OBJECTIVES

To investigate the evidence that nutrient and food intake modifies the risk of children developing allergy.

METHODS

We systematically searched 11 databases. Studies were critically appraised, and meta-analyses were undertaken.

RESULTS

We identified 62 eligible reports. There were no randomized controlled trials. Studies used cohort (n = 21), case-control (n = 15), or cross-sectional (n = 26) designs. All studies were judged to be at moderate to substantial risk of bias. Meta-analysis revealed that serum vitamin A was lower in children with asthma compared with controls (odds ratio [OR], 0.25; 95% CI, 0.10-0.40). Meta-analyses also showed that high maternal dietary vitamin D and E intakes during pregnancy were protective for the development of wheezing outcomes (OR, 0.56, 95% CI, 0.42-0.73; and OR, 0.68, 95% CI, 0.52-0.88, respectively). Adherence to a Mediterranean diet was protective for persistent wheeze (OR, 0.22; 95% CI, 0.08-0.58) and atopy (OR, 0.55; 95% CI, 0.31-0.97). Seventeen of 22 fruit and vegetable studies reported beneficial associations with asthma and allergic outcomes. Results were not supportive for other allergic outcomes for these vitamins or nutrients, or for any outcomes in relation to vitamin C and selenium.

CONCLUSION

The available epidemiologic evidence is weak but nonetheless supportive with respect to vitamins A, D, and E; zinc; fruits and vegetables; and a Mediterranean diet for the prevention of asthma. Experimental studies of these exposures are now warranted.

Clinical aspects of pediatric food allergy and failed oral immune tolerance

Food allergy seems to represent a new spectrum of disease that has elicited significant community concern and extended waiting lists for allergists and gastroenterologists alike. The apparent rise in prevalence of IgE-mediated food allergy (and associated risk of anaphylaxis) has been postulated to result from effects of a "modern lifestyle" but as yet clear environmental risk factors have not yet emerged. Family history seems to contribute to risk suggesting that gene-environment interactions will be important for identifying a subpopulation with increased susceptibility to any identified lifestyle effects. Non-IgE-mediated food allergy (including food-induced enteropathies and colitides, eosinophilic esophagitis, and Crohn's disease) with potentially similar environmental triggers resulting in diverse immune dysregulatory mechanisms. The evidence underpinning the putative rise in food allergy is discussed and potential mechanisms of disease explored. Clinical aspects of various food allergic conditions including non-IgE-mediated food allergy are outlined.

Role of nutrients in the development of neonatal immune response

Nutrients exert unique regulatory effects in the perinatal period that mold the developing immune system. The interactions of micronutrients and microbial and environmental antigens condition the post-birth maturation of the immune system, influencing reactions to allergens, fostering tolerance towards the emerging gastrointestinal flora and ingested antigens, and defining patterns of host defense against potential pathogens. The shared molecular structures that are present on microbes or certain plants, but not expressed by human cells, are recognized by neonatal innate immune receptors. Exposure to these activators in the environment through dietary intake in early life can modify the immune response to allergens and prime the adaptive immune response towards pathogens that express the corresponding molecular structures.

Cord serum immunoglobulin E as a risk factor for allergic symptoms and sensitization in children and young adults

Early markers of atopic predisposition are needed for targeting allergy preventive measures to high-risk infants. An elevated cord serum immunoglobulin E (CS-IgE) level is considered a risk factor for subsequent allergy in childhood. However, the previous studies have not assessed the predictive value of CS-IgE in a follow-up extended to adulthood. We aimed at clarifying whether CS-IgE is useful in predicting subsequent atopic manifestations up to age 20 yr. A cohort of 200 unselected, full-term newborns were prospectively followed up from birth to age 20 yr. The CS-IgE level was successfully measured in 190 subjects at birth. The subjects were re-examined at ages of 5, 11 and 20 yr with assessment of the occurrence of allergic symptoms during the preceding year, skin prick testing and measurement of serum total IgE. An elevated CS-IgE level was associated with allergic symptoms and skin prick test positivity at age 5 yr (p = 0.03 and 0.01), with allergic rhinoconjunctivitis at age 20 yr (p = 0.04) and with an elevated serum total IgE at ages of 11 and 20 yr (p = 0.02 and 0.01). The sensitivity of CS-IgE, i.e. the probability of an elevated CS-IgE in an infant who subsequently develops atopy, in predicting skin prick test-verified atopy at ages of 5 and 20 yr was 50% and 26%, respectively. The combination of elevated CS-IgE and positive family history of allergy was strongly associated with subsequent atopic manifestations. Nevertheless, it showed a reduced sensitivity as compared to CS-IgE or family history of allergy. We conclude that an elevated CS-IgE level predicts subsequent atopy up to age 20 yr.

Serum cholesterol level in infancy is inversely associated with subsequent allergy in children and adolescents. A 20-year follow-up study

BACKGROUND

Previous studies suggest an association between an altered lipoprotein profile and atopy. The association has been hypothesized to be due to alterations in the dietary fat intake, a factor possibly contributing to the increase of allergic diseases in industrialized countries.

OBJECTIVE

We aimed at assessing whether there is an association between the serum lipid levels in infancy and subsequent development of allergic symptoms in childhood and adolescence.

METHODS

A cohort of 200 unselected newborns was prospectively followed up from birth to age 20 years (from 1981 to 2002) with repeated measurements of total cholesterol from birth and throughout the first year of life. The subjects were re-examined at the ages of 5, 11 and 20 years, with assessment of the occurrence of allergic symptoms, skin prick testing (SPT) and measurement of total IgE and of the total, high- and low-density lipoprotein cholesterol.

RESULTS

Children and adolescents with allergic symptoms, SPT positivity and an elevated IgE had lower total cholesterol levels in infancy and childhood than the non-atopic subjects. The difference was not detectable in cord blood, but became significant from age 2 months onward.

CONCLUSION

The inverse association between the cholesterol level in infancy and subsequent manifestations of atopy seems not to be due to atopy-related dietary alterations, because it was already present in early infancy, when virtually all the infants were on a similar diet, i.e. on exclusive breastfeeding.