But it must be fresh, for lipases deteriorate in pooled mother's milk or cow's milk, particularly if it has been pasteurized. It is now known that during the first month of lactation, the nitrogen and protein content decline. In evolutionary terms, this weak premature infant should be culled out by a survival of the fittest process, but three advantages for the premature have been found in this well-designed milk. The ratio of cysteine to methionine is high, thereby overcoming the limited biosynthetic capabilities of the premature child to produce cysteine. Taurine, aminoethylsulfonic acid, which may be essential for neonates, is present in high concentrations in the mother's milk for prematurely born infants.
Taurine is very low in cow's milk.
The potentially toxic aromatic amino acids, phenylalanine, and tyrosine, are lower in concentration in human milk than in animal's milk. Human milk proteins are more easily assimilated by the child than the proteins in animals' milk. Some of these proteins are absolutely vital for the healthy development of the infant's immune system. In summary, the design of the milk is perfect in caloric content, amino acid concentrations, and in the enzyme concentrations of both lipase and lactase, ideally meeting the infant's needs. Its make-up far surpasses that of any formula, or even milk from animal sources.