Lactoferrin in milk

Lactoferrin is a major component of breast milk protein, constituting 10-15% of the total content. Each molecule of lactoferrin is capable of binding two atoms of iron and it has been proposed that lactoferrin is involved in iron absorption in the newborn infant. It is known that iron status of exclusively breast-fed infants usually is satisfactory to 6-9 months of age, in spite of a low iron content in breast milk. As a significant part of iron in human milk is bound to lactoferrin, it has been hypothesized that lactoferrin could aid in the delivery of iron to specific sites on the brush border membrane of the small intestine. Such lactoferrin receptors have now been isolated and characterized and may indeed facilitate cellular uptake of iron. Since lactoferrin is unusually stable against proteolytic enzymes, surviving molecules may help the infant to accrue breast milk iron during the neonatal period. It is also possible that lactoferrin in milk may have other biological effects in the infant, such as inhibiting bacterial growth, stimulating mucosal growth and proliferation, as well as modulating immune function. Bovine lactoferrin can now be obtained commercially and be used in infant formulae, but clinical evaluations of its effects have so far been disappointing. Recombinant human lactoferrin may also soon become available, but the effects of this form of lactoferrin have not yet been evaluated. It is possible that human lactoferrin in the context of human milk may have important biological functions in breast-fed infants, but it may be difficult to mimic these functions by the use of bovine lactoferrin or recombinant human lactoferrin added to infant formulae. Protein composition of human milk