Anemia of Prematurity - Portal Neonatal

Fore and hind milk - important differences
In addition to the changes from colostrum to mature milk that mirror the needs of the developing
neonate, variation exists within a given breastfeeding session. The milk first ingested by the infant (fore
milk) has a lower fat content. As the infant continues to breastfeed over the next several minutes, the fat
content increases (hind milk), which is thought to facilitate satiety in the infant. Finally, diurnal variations
in breast milk exist, which reflect maternal diet and daily hormonal fluctuations.
Specific enzymes to aid neonatal digestion
Various enzymes are components of human milk, some specific for the biosynthesis of milk components
in the mammary gland (eg, lactose synthetase, fatty acid synthetase, thioesterase) and others specific
for the digestion of proteins, fats, and carbohydrates that facilitate food breakdown and absorption of
human milk by the infant. Certain enzymes also serve as transport moieties for other substances such
as zinc, selenium, and magnesium.
Three-dimensional structure of human milk
Under a microscope, the appearance of human milk is truly amazing. While a fluid, human milk has
substantial structure in the form of compartmentation. Within the various compartments of human milk,
nutrients and bioactive substances are sequestered. The most elegant example of this structure
involves lipids. Lipids are enveloped at the time of secretion from the apical mammary epithelial cell
within its plasma membrane, becoming the milk-fat globule. Certain proteins, growth factors, and
vitamins also become sequestered within this milk-fat globule and are embedded within the membrane
itself.
The membrane acts as a stabilizing interface between the aqueous milk components and
compartmentalized fat. This interface allows controlled release of the products of lipolysis and transfer of
polar materials into milk serum (aqueous phase). The bipolar characteristics of the membrane are also
necessary for the emulsion stability of the globules themselves; thus, the structure of human milk
provides readily available fatty acids and cholesterol for micellar absorption in the small intestine.
Proteins, carbohydrates, and designer fats for optimal brain development
Human milk provides appropriate amounts of proteins (the major components of which are alphalactalbumin
and whey), carbohydrates (lactose), minerals, vitamins, and fats for the growing term infant.
The fats are comprised of cholesterol, triglycerides, short-chain fatty acids, and long-chain
polyunsaturated (LCP) fatty acids. The LCP fatty acids (18- to 22-carbon length) are needed for brain
and retinal development. Large amounts of omega-6 and omega-3 LCP fatty acids, predominately the
20-carbon arachidonic acid (AA) and the 22-carbon docosahexaenoic acids (DHAs), are deposited in
the developing brain and retina during prenatal and early postnatal growth.
An infant, particularly a preterm infant, may have a limited ability to synthesize optimal levels of AA and
DHA from linoleic and linolenic acid. These 2 fatty acids may be essential. Recently, some infant
formulas in the United States have added AA or DHA. Increasing evidence suggests that breastfed
infants have better visual acuity at 4 months and slightly enhanced cognitive development than formulafed
infants, even when socioeconomic factors are taken into account. These differences are more
pronounced in premature infants. Rather than causing better vision or greater intelligence, breast milk
may somehow protect the developing neonatal brain from injury or less optimal development by
providing necessary building materials and growth factors.