Definitions
First up, some definitions for some extra clarity:
- Infant- A child aged between 0-12 months.
- Newborn or neonate- An infant in the first 28 days of life.
- Preterm- Infant born before 37 weeks gestation.
- Very preterm- Infant born between 28 weeks and 31 weeks + 6 days gestation.
- Extremely preterm- Infant born before 28 weeks gestation.
Babies who are born very or extremely preterm may need to be fed parentally at first, and then drip-fed milk. Premature babies may have underdeveloped GI tracts that cannot handle a rapid feed, so feeding them rapidly may increase the risk of necrotising enterocolitis (NEC).
Breastmilk
You've probably heard the saying that "breast is best." In fact, the World Health Organisation and UNICEF recommend that babies are fed exclusively breast milk in the first six months of life, and that breast milk continues to be the primary food for the first year of life. It is also recommended to continue to breastfeed for two years or even longer.
Why is breast milk so good? It's got lots of good stuff in it, such as:
Proteins
Proteins, which are found in higher concentrations in colostrum (milk in first few days after giving birth) as compared to regular breast milk, are needed for growth of lean tissue. The main proteins in breast milk are caseins, whey proteins and milk fat globule proteins. Important whey proteins include lactoferrin, alpha-lactalbumin, lysozyme, secretory IgA and bile-salt-stimulated lipase. Lactoferrin binds to iron, reducing the amount of iron available for pathogens, and thus has bacteriostatic effects. Alpha-lactalbumin has a good amino acid profile, making it suitable for promoting the growth of the gut microbiome. Lysozyme and secretory IgA both have important immune functions, while bile-salt-stimulated lipase aids in the digestion of milk lipids. Whey proteins are somewhat resistant to digestion by the baby's gut, so they can hang around and exert their goodness for a while.
Carbohydrates
The main carbohydrate in breast milk is lactose, but it isn't the only one. Other important carbohydrates include the human milk oligosaccharides (HMO), which consist of a large variety of oligosaccharides (3-10 monosaccharides) that are resistant to digestion. HMOs are prebiotic (support growth of the gut microbiome), inhibit virus and bacteria binding, and are a source of sialic acid, which supports brain development and cognition. At least one HMO is associated with reduced risk of necrotising enterocolitis.
Fats
Breast milk contains plenty of saturated and polyunsaturated long-chain fatty acids. The total fat content is independent of the maternal diet, but the fatty acid profile depends on maternal diet, so mothers should make sure to eat a diet with a good fatty acid profile. Fats are actively transported from the maternal blood through lactocytes in order to get to the milk.
The main saturated fatty acids in breast milk are palmitic and stearic acids, which are important energy sources. Around 60% of palmitic acid in human breast milk is esterified at the sn-2 position of glycerol, which is different to cow's milk and formula in which esterification occurs at sn-1 and sn-3. It is thought that the esterification in cow's milk and formula may increase calcium binding to palmitate, leading to hard stools in babies fed formula (as opposed to breast milk).
The main polyunsaturated fatty acids in breast milk include linoleic and linolenic acids (both essential fatty acids), decosahexanoic acid (DHA) and eicosapentanoic acid (EPA) (incorporated into cell membranes and are essential for retinal and brain development), and arachidonic acid. The optimal ω-6/ω-3 ratio is around 5.
Micronutrients
Breast milk contains a lot of micronutrients such as vitamins, iron and iodine. However, the concentrations of such nutrients depends on the mother's diet.
Prebiotics?
Breast milk contains bacteria that may be important for the gut health of the infant. This is still a growing area of research, so watch this space...
"Nutritional supplements" for infants
Unfortunately, not all mothers can breastfeed, for various reasons. As such, other possible "supplements" are being researched. Bovine colostrum has been shown to be beneficial in neonatal growth, digestive function and gut immunity, while bovine lactoferrin (which is 70% homologous with human lactoferrin) may reduce the risk of necrotising enterocolitis.
Formula
Formula is pretty much always the go-to for mothers who cannot breastfeed. All formulae have certain nutrients that are required by law. In addition, there are laws that state that no health claims can be made for formulae designed for infants (i.e. <12 months of age).
Introducing solids
Solids can be introduced at around 6 months, or even slightly earlier. It is important that the first foods given are rich in protein and iron, as these are the first nutrients to become deficient. Foods can be introduced in pretty much any order, at a rate that suits the infant. Once the child is older than 12 months, they can usually eat the same foods as the rest of the family.
Only one more content lecture left for the rest of semester (for PATH3304)! Almost there!
Micronutrients
Breast milk contains a lot of micronutrients such as vitamins, iron and iodine. However, the concentrations of such nutrients depends on the mother's diet.
Prebiotics?
Breast milk contains bacteria that may be important for the gut health of the infant. This is still a growing area of research, so watch this space...
"Nutritional supplements" for infants
Unfortunately, not all mothers can breastfeed, for various reasons. As such, other possible "supplements" are being researched. Bovine colostrum has been shown to be beneficial in neonatal growth, digestive function and gut immunity, while bovine lactoferrin (which is 70% homologous with human lactoferrin) may reduce the risk of necrotising enterocolitis.
Formula
Formula is pretty much always the go-to for mothers who cannot breastfeed. All formulae have certain nutrients that are required by law. In addition, there are laws that state that no health claims can be made for formulae designed for infants (i.e. <12 months of age).
Introducing solids
Solids can be introduced at around 6 months, or even slightly earlier. It is important that the first foods given are rich in protein and iron, as these are the first nutrients to become deficient. Foods can be introduced in pretty much any order, at a rate that suits the infant. Once the child is older than 12 months, they can usually eat the same foods as the rest of the family.
Only one more content lecture left for the rest of semester (for PATH3304)! Almost there!
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