Background: The nutritional composition of breast milk, coupled with the health advantages of breastfeeding, are reasons that advisory bodies recommend this form of infant feeding as best practice. Evidence investigating the association between breastfeeding and the prevalence of allergies has, however, been highly inconclusive. Research has shown that breastfeeding has a protective effect on the early development of allergic asthma (Kull, 2002), whilst other evidence showed there to be no significant association (Fergusson, 1983). Paradoxically, other research has even shown breastfeeding increases the risk of children developing allergic asthma (Sears, 2000). This systematic review aimed to examine the evidence relating breastfeeding and allergic asthma among children up to 7 years of age.
Methods: A systematic review process was utilised. Different terminologies for breastfeeding and allergic asthma were nested; breastfeeding and breast-feeding were combined with either asthma, allergic, atopic or extrinsic asthma and used in four databases; Google Scholar; PubMed; Web of Knowledge and CAB abstracts. The papers identified were compared against pre-defined inclusion and exclusion criteria. The paper must have: an abstract available; been written in English; used objective and valid diagnostic methodology for defining asthma and atopy in children up to 7 years of age and studied comparable groups of children given breast milk or alternative milks. References acknowledged by the selected papers were sourced and subjected to the same inclusion and exclusion criteria. The quality of the research selected was assessed using a scale adapted from the Newcastle–Ottawa Scale (Wells, 2001). An overall judgement of the quality of the research was made by the researcher. The same terminology and the database Cochrane Reviews were used to identify any relevant reviews that had previously been published.
Results: One thousand seven hundred and eighty-three papers were identified. Of these, 562 were excluded because of their publication date, their apparent irrelevance based on their title (n = 717) or by use of the defined inclusion criteria (n = 497). This gave a final sample selection of seven papers.
Breastfeeding had a protective effect for the risk of developing asthma. Children who had been breastfed for any period were less likely to have developed asthma by 7 years of age than those who had only been given formula milk. This risk reduction was more common among children who had been breastfed for longer periods of time compared with children who had been breastfed for only a short period. There was no significant difference in the prevalence of allergic sensitisation among children who had been breastfed compared with those given artificial milks.
Discussion: Breastfeeding helps to protect children up to 7 years of age from developing asthma. Despite advisory bodies promoting breastfeeding for its protective effect on the development of allergies, evidence showed the benefits were not significant in reducing the risk of atopy. Collectively, breastfeeding does not protect against allergic asthma in children up to 7 years of age. It is unfortunate that mothers are being encouraged to breastfeed their infants for its protective effect on the development of allergies when evidence is not significant.
Conclusion: There are many benefits of breastfeeding but current evidence does not support its effect on reducing the risk of children up to 7 years of age developing allergic asthma.
References: Kull, I., Wickman, M., Lilja, G., Nordvall, S. & Pershagen, G. (2002) Breast feeding and allergic diseases in infants – a prospective birth cohort study. Arch. Dis. Child.87, 478–481
Fergusson, D. Horwood, L. & Shannon, F. (1983) Asthma and Infant Diet. Arch. Dis. Child.58, 48–51.
Sears, M., Greene, J., Taylor, D., Flannery, E., Cowan, J., Herbison, G. & Poulton, R. (2000) Long-term Relation Between Breastfeeding and Development of Atopy and Asthma in Children and Young Adults: A Longitudinal Study. Lancet360, 901–907.
Wells, G., O’Connell, D., Peterson, J., Welch, V., Losos, M. & Tugwell, P. (2001) Ottawa Health Research Institute; The Newcastle-Ottawa Scale for Assessing the Quality of Nonrandomised Studies in Meta-analyses; available at http://www.ohri.ca/programs/clinical_epidemiology/nosgen.pdf.