The importance of early complementary feeding in the development of oral tolerance: Concerns and controversies

Abstract

Rising rates of food allergies in early childhood reflect increasing failure of early immune tolerance mechanisms. There is mounting concern that the current recommended practice of delaying complementary foods until 6 months of age may increase, rather than decrease, the risk of immune disorders. Tolerance to food allergens appears to be driven by regular, early exposure to these proteins during a 'critical early window' of development. Although the timing of this window is not clear in humans, current evidence suggests that this is most likely to be between 4 and 6 months of life and that delayed exposure beyond this period may increase the risk of food allergy, coeliac disease and islet cell autoimmunity. There is also evidence that other factors such as favourable colonization and continued breastfeeding promote tolerance and have protective effects during this period when complementary feeding is initiated. This discussion paper explores the basis for concern over the current recommendation to delay complementary foods as an approach to preventing allergic disease. It will also examine the growing case for introducing complementary foods from around 4 months of age and maintaining breastfeeding during this early feeding period, for at least 6 months if possible.

Food Allergy and the Oral Immunotherapy Approach

“…Therefore, in the oral tolerance induction there is a critical ''window period'' to reduce the risk of allergy. Although the timing of this window to prevent allergies is not completely clear, current evidence suggests that this is most likely to be located between the 4th (around 17 weeks) and the 7th month of life (Prescott et al 2008). In this regard, Koplin et al (2010) have found that infants who were introduced to cooked egg at 4-7 months had the lowest risk of developing an allergy to eggs.…”

Asociación entre los patrones alimentarios durante el primer año de vida y alergia alimentaria en lactantes

“…3 La base genética no puede ser modificada, 4 pero existen factores ambientales que modulan la aparición de la alergia alimentaria; 5 en este contexto, el rol de la dieta durante el primer año de vida podría ser determinante. 6 Las alergias alimentarias son más frecuentes en lactantes, presumiblemente por la inmadurez de mecanismos inmunológicos y no inmunológicos que previenen el ingreso de antígenos a través de la barrera gastrointestinal. 7,8 Leche, huevo y maní son los alérgenos alimentarios más comunes en la temprana infancia y en la niñez.…”

Infant nutrition and allergy

“…Until very recently, for infants with a family history of allergy expert guidelines recommended delaying introduction of allergenic foods (including avoiding eggs until 2 years and nuts until 3 years of age), as well as delaying solid foods until after 6 months and continuation of breast-feeding for at least 12 months (8,13,32) . These recommendations have been challenged by recent population studies, creating the concern that the current practice of delaying complementary foods until 6 months of age may increase, rather than decrease, the risk of immune disorders (1,9,13,(33)(34)(35) . In a systematic review of thirteen studies, five studies found a positive association between early introduction of solid foods (before 4 months of age) and eczema, one study found an association with pollen allergy, and others reported no association between early introduction of solid foods and the development of allergic diseases (36) .…”

“…In contrast, Sariachvili et al showed that early introduction (within the first 4 months) of solid foods was associated with a reduced risk for eczema among children with allergic parents, whereas no significant effect was found among children with non-allergic parents (37) . Furthermore, a review by Prescott et al showed an increased risk of allergy if solids were introduced before 3-4 months (34) . Some other prospective studies supported neither prolonged breast-feeding nor delayed introduction of solid foods for the prevention of allergic diseases in children (9,35) .…”

“…Based on the current available data, it was proposed that early complementary food introduction may hasten and/or maintain oral mucosal tolerance rather than increase the risk of food allergy (30) . Tolerance to food allergens appears to be driven by regular, early exposure to these proteins during a 'critical early window' of development (34) . Although the timing of this window is not clear, current evidence suggests that this is most likely to be between 4 and 6 months of life and that delayed exposure beyond this period may increase the risk of food allergy, coeliac disease and islet-cell autoimmunity (8,33,34) .…”