Immunonutrition in early life: diet and immune development.

The belief that “you are what you eat” originated from Brillat-Savarin et al. (“tell me what you eat, and I will tell you who you are”) in the 1800s [1] was the starting point in the quest to understand the role of diet in almost every function in the body and in overall health. However, prior to the 1950s, there was little recognition of the relationship between nutrition and immune function. Scrimshaw and colleagues first described the bidirectional interaction between nutrition and infection [2]. This initial link between malnutrition and infective diseases has since evolved; not only do we now consider that diet is critical in maintaining optimal immune function, but it is widely accepted that almost all nutrients in the diet play a crucial role in maintaining an “optimal” immune response, and that both deficiency and excessive intakes can have negative consequences in terms of immune status and susceptibility to a variety of pathogens [3]. Dietary components with immunomodulatory potential include vitamins, minerals, polyphenols, dietary polyunsaturated fatty acids (PUFAs), and dietary components with the ability of modulating the gut microbiota (fibre, prebiotics, and probiotics). Although extensive research (experimental and clinical) demonstrates the properties of some of these dietary components, in many cases the exact mechanisms remain unclear. The impact of particular nutrients has been investigated by both epidemiological and intervention studies, but there are relatively few studies dealing with immune development in early life and in subjects with common immune-mediated diseases in early life (coeliac disease or asthma/allergies).