Lactoferrin in human milk: its role in iron absorption and protection against enteric infection in the newborn infant.

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This is a general discussion with references to relevant literature dealing with the substance lactoferrin in human milk. Its structure and biochemical properties are explained. Most of these structural and biochemical studies have been carried out with proteins of human or bovine origin. The iron-saturated form of lactoferrin seems to remain relatively intact within the gastrointestinal tract of neonates due to the low level of appreciable peptic activity in newborn infants. Breast milk does though contain factors which actively promote iron absorption. Especially as the infant matures its need for exogenous iron increases milk lactoferrin levels decrease and proteolytic activity increases resulting in progressively more iron being released from the lactoferrin. Once released absorption of this iron is facilitated. Many studies most with human and guinea pig subjects have shown that lactoferrin has the ability to inhibit growth of certain microorganisms in the gut of newborn infants. In the milk of other species e.g. the cow pig and dog lactoferrin levels are too low to provide this protection. It is concluded that a main function of lactoferrin may be to control iron absorption in newborns.