Human milk oligosaccharides and polyphenols: Mechanisms, effects, and applications in allergies

Human milk offers the best nutrition to the infant, which is crucial for the child's proper development and health status across the lifespan. Besides providing the substances optimally supplying the baby with energy and building materials, breast milk contains several immunometabolically active components. Those include molecules fully de novo synthesized by the mother, such as human milk oligosaccharides (HMO), and substances of nonhuman origin, transferred to the infant through mother's milk, such as dietary plant polyphenols. In this review, we outline the basic biology of HMO and polyphenols and deeply characterize their effects on the development of allergic disorders on the basis of available literature reporting data from in vitro, animal, and human studies. Further, we review the abundance of HMO and polyphenols, commonly present in mother's milk, and their mutual interactions in the context of the mechanisms underlying predisposition to, or protection against, the development of allergies. Finally, we discuss the potential of HMO and polyphenols in allergy prevention and therapy.