The clinical expression of allergy in breast-fed infants

Nutritionally mediated programming of the developing immune system

A growing body of evidence highlights the importance of a mother's nutrition from preconception through lactation in programming the emerging organ systems and homeostatic pathways of her offspring. The developing immune system may be particularly vulnerable. Indeed, examples of nutrition-mediated immune programming can be found in the literature on intra-uterine growth retardation, maternal micronutrient deficiencies, and infant feeding. Current models of immune ontogeny depict a "layered" expansion of increasingly complex defenses, which may be permanently altered by maternal malnutrition. One programming mechanism involves activation of the maternal hypothalamic-pituitary-adrenal axis in response to nutritional stress. Fetal or neonatal exposure to elevated stress hormones is linked in animal studies to permanent changes in neuroendocrine-immune interactions, with diverse manifestations such as an attenuated inflammatory response or reduced resistance to tumor colonization. Maternal malnutrition may also have a direct influence, as evidenced by nutrient-driven epigenetic changes to developing T regulatory cells and subsequent risk of allergy or asthma. A 3rd programming pathway involves placental or breast milk transfer of maternal immune factors with immunomodulatory functions (e.g. cytokines). Maternal malnutrition can directly affect transfer mechanisms or influence the quality or quantity of transferred factors. The public health implications of nutrition-mediated immune programming are of particular importance in the developing world, where prevalent maternal undernutrition is coupled with persistent infectious challenges. However, early alterations to the immune system, resulting from either nutritional deficiencies or excesses, have broad relevance for immune-mediated diseases, such as asthma, and chronic inflammatory conditions like cardiovascular disease.

What are the risks associated with formula feeding? A re-analysis and review

BACKGROUND

Most infant feeding studies present infant formula use as "standard" practice, supporting perceptions of formula feeding as normative and hindering translation of current research into counseling messages supportive of exclusive breastfeeding. To promote optimal counseling, and to challenge researchers to use exclusive breastfeeding as the standard, we have reviewed the scientific literature on exclusive breastfeeding and converted reported odds ratios to allow discussion of the "risks" of any formula use.

METHODS

Studies indexed in PubMed that investigated the association between exclusive breastfeeding and otitis media, asthma, types 1 and 2 diabetes, atopic dermatitis, and infant hospitalization secondary to lower respiratory tract diseases were reviewed. Findings were reconstructed with exclusive breastfeeding as the standard, and levels of significance calculated.

RESULTS

When exclusive breastfeeding is set as the normative standard, the re-calculated odds ratios communicate the risks of any formula use. For example, any formula use in the first 6 months is significantly associated with increased incidence of otitis media (OR: 1.78, 95% CI: 1.19, 2.70 and OR: 4.55, 95% CI: 1.64, 12.50 in the available studies; pooled OR for any formula in the first 3 mo: 2.00, 95% CI: 1.40, 2.78). Only shorter durations of exclusive breastfeeding are available to use as standards for calculating the effect of "any formula use" for type 1 diabetes, asthma, atopic dermatitis, and hospitalization secondary to lower respiratory tract infections.

CONCLUSIONS

Exclusive breastfeeding is an optimal practice, compared with which other infant feeding practices carry risks. Further studies on the influence of presenting exclusive breastfeeding as the standard in research studies and counseling messages are recommended.

Breast-feeding and the onset of atopic dermatitis in childhood: a systematic review and meta-analysis of prospective studies

BACKGROUND

Despite the numerous studies on the possible protective effect of breast-feeding against the onset of atopic dermatitis during childhood, this issue remains controversial.

OBJECTIVE

We conducted a systematic review with meta-analysis of prospective studies that evaluated the association between exclusive breast-feeding during the first 3 months after birth and atopic dermatitis.

METHODS

A comprehensive search of the 1966-2000 MEDLINE database and review of the reference lists of relevant articles identified 18 prospective studies that met the predefined inclusion criteria. By means of a standardized approach, 2 of the investigators independently assessed the methodologic quality of the studies, duration and exclusivity of breast-feeding, outcome measures, and control for potential confounding factors. The same approach was applied during data abstraction and evaluation of the estimates of association. Summary measures of association were then calculated.

RESULTS

The summary odds ratio (OR) for the protective effect of breast-feeding in the studies analyzed was 0.68 (95% confidence interval [CI], 0.52-0.88). This effect estimate was higher in the group of studies wherein children with a family history of atopy were investigated separately (OR = 0.58; CI, 0.41-0.92) than in those of combined populations (OR = 0.84; CI, 0.59-1.19). A small subset of studies of children without a history of atopy in first-degree relatives showed no association between breast-feeding and the onset of atopic dermatitis (OR = 1.43; CI, 0.72-2.86).

CONCLUSION

Exclusive breast-feeding during the first 3 months of life is associated with lower incidence rates of atopic dermatitis during childhood in children with a family history of atopy. This effect is lessened in the general population and negligible in children without first-order atopic relatives. Breast-feeding should be strongly recommended to mothers of infants with a family history of atopy, as a possible means of preventing atopic eczema.

Association between breast feeding and asthma in 6 year old children: findings of a prospective birth cohort study

OBJECTIVES

To investigate the association between the duration of exclusive breast feeding and the development of asthma related outcomes in children at age 6 years.

DESIGN

Prospective cohort study.

SETTING

Western Australia.

SUBJECTS

2187 children ascertained through antenatal clinics at the major tertiary obstetric hospital in Perth and followed to age 6 years.

MAIN OUTCOME MEASURES

Unconditional logistic regression to model the association between duration of exclusive breast feeding and outcomes related to asthma or atopy at 6 years of age, allowing for several important confounders: sex, gestational age, smoking in the household, and early childcare.

RESULTS

After adjustment for confounders, the introduction of milk other than breast milk before 4 months of age was a significant risk factor for all asthma and atopy related outcomes in children aged 6 years: asthma diagnosed by a doctor (odds ratio 1.25, 95% confidence interval 1.02 to 1.52); wheeze three or more times since 1 year of age (1.41, 1.14 to 1.76); wheeze in the past year (1.31, 1.05 to 1.64); sleep disturbance due to wheeze within the past year (1.42, 1.07 to 1.89); age when doctor diagnosed asthma (hazard ratio 1.22, 1.03 to 1.43); age at first wheeze (1.36, 1.17 to 1.59); and positive skin prick test reaction to at least one common aeroallergen (1.30, 1.04 to 1.61).

CONCLUSION

A significant reduction in the risk of childhood asthma at age 6 years occurs if exclusive breast feeding is continued for at least the 4 months after birth. These findings are important for our understanding of the cause of childhood asthma and suggest that public health interventions to optimise breast feeding may help to reduce the community burden of childhood asthma and its associated traits.