Neoformed Compounds from the Maillard Reaction in Infant Formulas: a New Risk Factor for Allergy?

Food allergies, which are T helper cell Type 2 aberrant responses of the immune system to food proteins, are increasing. Environmental factors, including food contaminants, are often mentioned to explain this increase. Heat treatment of food induces the Maillard reaction, a non-enzymatic reaction between reducing sugars and free amino groups of proteins or free amino acids. This leads to the genesis of neoformed compounds, including advanced Maillard reaction products (also called dietary advanced glycation end-products [AGEs]). Infant formulas are very sensitive to the Maillard reaction because of their high content of lactose and proteins and their long shelf life. The dietary AGEs content is particularly high in hydrolysed infant milk. Among dietary AGEs, Nε-carboxymethyllysine is the main form in milk. An increasing number of studies show potentially deleterious effects of dietary AGEs, including inflammation genesis. These effects seem to be in a great part dependent on the receptor of AGEs (RAGE). RAGE is present on immune cells and studies have shown that RAGE is involved in T helper cell priming, proliferation, and differentiation. Moreover, there is increasing evidence that the Maillard reaction enhances the allergenicity of proteins. All these data indicate a potential role of dietary AGEs in allergies. Nevertheless, the impact of dietary AGEs on the immune system favouring the T helper cell Type 2 profile and consequently predisposition to develop allergy is poorly documented and needs further investigation.