Abstract
Breast milk is the best source of nutrition that provides the energy and nutrients needed for the ideal growth and development of newborns and infants. Besides, breast milk includes various bioactive compounds, which protects infants against infectious agents and antigens and contributes to immune maturation, organ development and microbial colonization. Breast milk is dynamic; the composition of the nutrients and the content of immunological active compounds may change in each stage of lactation. During the early stages of lactation, biological and immunological active compounds provide additional support to the development of the neonatal immune system. After these stages, the composition of breast milk continues to provide appropriate energy and nutrients according to the infant needs, in order to protect neonatal immune system and maintain the development and growth of infants. Immunological maturation during the fetal life and the first months of life is provided by immunoglobulins in breast milk, which are among the most important immune protective factors and transferred to infants through breastfeeding. Due to their biological characteristics, Secretory Immunoglobulin A (SIgA) antibodies are the most important antibodies in breast milk, which provide the first defense against the antigens in the intestines of infants. In addition to antibodies, enzymes, including active leukocytes, cytokines, oligosaccharides, lactoferrin, lysozyme and lactoperoxidase, as well as biological and immunological factors, such as hormones, growth factors, bioactive peptides, nucleotides and fatty acids are transferred to infants through breastfeeding. There is now a growing body of evidence suggesting that breastfeeding protects infants against many infections such as gastrointestinal system and respiratory tract infections, strengthens immune system and provides protective effects against allergic and autoimmune diseases in later life.
Highlights
Breast milk is a unique source of nutrition that meets the nutritional and physiological needs of the newborn
Several studies in the literature show that breast milk maintains defense against infections and allergic diseases, the results of the studies investigating the effects of breastfeeding on atopic diseases are conflicting
One of the studies found that IgA concentrations in the breast milk of atopic mothers were lower compared to breast milk of non-atopic mothers, but this was not related to the development of food allergy in children [61]
Summary
Breast milk is a unique source of nutrition that meets the nutritional and physiological needs of the newborn. Breast milk contains living cells and biologically and immunologically active agents, including leukocytes (polymorphonuclear neutrophils, monocytes/macrophages, lymphocytes), cytokines, inflammatory mediators, signaling molecules, hormones, growth factors, soluble receptors, oligosaccharides, polyunsaturated fatty acids and various microbiomes [25] [26] [27]. All these agents interact with each other and the mucous membranes of the digestive and upper respiratory tracts of infants, providing passive immunity and strengthening the immune system [5]. SIgA maintains immune defense for infants by preventing bacterial colonies and the translocation across the mucosal barrier [5] [6] [8] [28] [31]
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