Beneficial actions of breast milk Why and how?

Breast feeding not only reduces the risk of necrotizing enterocolitis, atopy, and infection, and improves cognitive development but also protects against development of obesity, diabetes mellitus, hypertension, and imparts a favorable lipid profile in adult life. Human breast milk contains adequate amounts of protein, fat, carbohydrates, lactose, casein, more than 200 short-chain human milk oligosaccharides (HMOs), vitamins, carotenoids, interleukin-10 (IL-10), tumor necrosis factor-alpha (TNF-alpha) and several antibodies in the form of secreted immunoglobulin A (IgA) that support somatic growth and help the infant to develop robust populations of memory T cells {including T helper 17 (IL-17) cells} and a healthy gut microbiota. Presence of polyunsaturated fatty acids (PUFAs) and their hydroxy fatty acid precursors including pro-inflammatory leukotriene B4 (LTB4) and anti-inflammatory and pro-resolving lipoxin A4 (LXA4), resolvin D1 (RsvD1) and resolvin E1 (RsvE1) in human breast milk will ensure prevention of inappropriate inflammation. PUFAs and their metabolites serve as ligands for the retinoid X receptor (RXR) in brain, an obligatory component of a large number of nuclear receptor heterodimers to which vitamin A metabolite, 9-cis retinoic acid, binds with high affinity. These retinoic acid (RA) receptors (RAR alpha, RAR beta, and RAR gamma) and the retinoid X receptors (RXR alpha, RXR beta, RXR gamma) function as RAR-RXR heterodimers to support embryonic development and post-natal life and in the regulation of various neurotransmitter pathways and enhance intelligence quotient (IQ).