[Past and present status in the design of infant formulas]

This paper describes briefly the history of infant foods, from the alternate ways of feeding developed during the late 19th century to the present-day infant formulas, and enumerates the different available types (milk-based, soy-based, hypoallergenic, lactose-free, etc,). Among the nutritional aspects the main characteristics of formulation are emphasized, especially within the nitrogen, fat and mineral fractions. Considering the nitrogen fraction, it must be taken into account that the amino acid profiles in milk-based formulas differ according to the casein/whey proteins ratio (either 80:20 or 40:60 in the so-called "adapted" or "humanized"). On the other hand, it has been recognized recently that some non-protein components of human milk, such as taurine, carnitine and nucleotides, are relevant to infant nutrition and therefore, they are being included in some formulas. Regarding fat, essential fatty acids supply is very important; present recommendations stress the importance of providing n-6 to n-3 series ratios close to that found in human milk and also a preformed supply of long-chain polyunsaturated fatty acids. Among minerals, bioavailability and relative proportions of trace elements are important issues in formulation. Other concepts of relevance are the renal solute load and the osmolarity because of their effect on neonate's metabolism.