Matching Human-Milk Composition and Breastfeeding Performance

CHALLENGES OF MATCHING HUMAN-MILK COMPOSITION AND BREASTFEEDING PERFORMANCE 

Infant formula manufacturers have made changes to formulas in order to match either human milk composition or breastfeeding performance (Benson and Masor, 1994). The term breastfeeding performance is used because, with the exception of one study of preterm infants (Lucas et al., 1994), all other studies comparing human milk with formulas involved breastfeeding— not providing human milk from a bottle. 

Historically one approach to match human-milk composition is to add new ingredients (see Appendix B for the composition of formulas and human milk). This turns out to be a quixotic quest since human milk is a complex body fluid that is variable not only among individuals, but within an individual over time. In addition, it contains components, such as live cells and bioactive compounds, that either cannot be added to formulas or cannot survive a shelf life. Finally, not all human-milk constituents are essential some, like LC-PUFAs, docosahexaenoic acid (DHA), and arachidonic acid (ARA), can be synthesized by term and preterm infants born at 33 weeks gestation (Uauy et al., 2000). 

Manufacturers who wish to add some, but not all, ingredients found in human milk may defeat the purpose of the added nutrients or may potentiate negative interactions. Examples include the deleterious effect on growth when eicosapentaenoic acid is added without adequate DHA (Carlson et al., 1996) and the potential negative effect of adding polyunsatu- 

Manufacturers must also consider the form of the molecule in which a nutrient is presented to the intestine and its bioavailability. For example, the high bioavailability of iron from lactoferrin in human milk allows for a much lower concentration of iron in human milk (0.2-0.4 mg/L) compared with infant formulas (4.0-12 mg/L) and thereby decreases competition between iron and other divalent cations, such as copper and zinc (Lonnerdal and Hernell, 1994). 

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