Although the role of breast-feeding in the prevention of allergic diseases is not clear, there is no evidence that any other food resources before 4 to 6 month of life could be superior in any aspect. Maybe the main issue that allows questions about the protective effects of breast-milk is it is not possible randomise breast-feeding, which is always a confounding variable. Many of the studies that claim about the lack of protection of breast-feeding or even that breast milk could increase the risk of allergies have been non-randomised, retrospective or observational in design and, thus, inconclusive.
Several studies have reported higher protection with exclusive breast-feeding and some have observed a better effect in children considered as “high risk for atopy”. Regarding the protective effect of breastfeeding on the development of asthma in infancy and childhood, there are some evidences that breastfeeding induces tolerance when lactating mothers are exposed to allergens. In this process, the presence of TGF-b in breast milk appears as a critical factor for tolerance induction toward antigen transmitted to the babies. Together, allergen and TGF-b are sufficient to induce T-cell differentiation and the resulting CD4+ regulatory T cells provide offspring with allergen-specific protection in a mouse model of human asthma.
Similarly, protective effects of breastfeeding an infant were found in a systematic review with meta-analysis of prospective studies that evaluated exclusive breastfeeding during the first 3 months after birth and atopic dermatitis. The authors found that exclusive breastfeeding during the first 3 months of life was associated with lower incidence of atopic dermatitis during childhood in children with a family history of atopy (infants with at least one first-degree relative [parent or sibling] with allergic disease). Further studies confirmed this effect protection in children with a family history of atopy, but the same conclusion cannot be made for children not at high risk for allergic disease.
The relationship between breastfeeding and food allergy is not clear, but an analysis of published peer-reviewed observational and interventional studies found that feeding exclusively human milk for at least 4 months was associated with a lower cumulative incidence of cow´s milk allergy until 18 months of age. Although the American Academy of Pediatrics could not make any firm conclusions about the role of breastfeeding and development of general food allergy, there is enough evidences to support its role at least on cow´s milk allergy.
When compared with breast-feeding with supplemental cow’s milk formula, exclusive breast-feeding for 4 months showed a protective effect on developing allergy in infants at high risk. Breast-feeding with supplemental hydrolysed formula (both partially and extensively hydrolysed) also showed a positive effect compared with breast-feeding with supplemental cow’s milk formula. However, breastfeeding with supplements of hydrolysed formulas showed no advantage compared with exclusive breast-feeding.
No matter the history of family atopy, due to the countless advantages of breast milk as the optimal form of feeding for children in the first months of life, exclusive breast-feeding should always be encouraged at least the first 4 months of life and continued at least up to 2 years-old (World Health Organization).
References:
- Verhasselt V. Neonatal tolerance under breastfeeding influence. Curr Opin Immunol. 2010;22(5):623-30.
- Mosconi E, Rekima A, Seitz-Polski B, Kanda A, Fleury S, Tissandie E, Monteiro R, Dombrowicz DD, Julia V, Glaichenhaus N, Verhasselt V. Breast milk immune complexes are potent inducers of oral tolerance in neonates and prevent asthma development. Mucosal Immunol. 2010;3(5):461-74.
- Verhasselt V. Neonatal tolerance under breastfeeding influence: the presence of allergen and transforming growth factor-beta in breast milk protects the progeny from allergic asthma. J Pediatr. 2010;156(2 Suppl):S16-20.
- Kneepkens CM, Brand PL. Clinical practice: Breastfeeding and the prevention of allergy. Eur J Pediatr. 2010;169(8):911-7.
- Thygarajan A, Burks W. American Academy of Pediatrics recommendations on the Effects of Early Nutritional Interventions on the Development of Atopic Disease. Curr Opin Pediatr. 2008;20(6): 698–702.
- Mizak Z. Infant nutrition and allergy. Proc Nutr Soc. 2011;70(4):465-71.