Biology to advancements in other areas. Composition of Breastmilk:

Biology Assignment 1


Introduction: Due to a variety of possible reasons, a mother may not be able to or want to breastfeed their child. The child will still require the nutrients that milk provides thus mother began searching for alternative solutions. Wet nursing was the first but the prospect garnered a negative image in the eyes of society at large. Stevens (2009) noted that the creation of infant formula was only possible due to advancements in other areas.

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Composition of Breastmilk: Breastmilk is not like most other liquids because it is alive and as such, it has a constantly changing composition. The values that will be used here are only averages taken from certain time periods after the mother has given birth.

Mammalian milk consists of variable amounts of water, triglyceride fats, a large number of carbohydrates (primarily lactose, that is, milk sugar), proteins, vitamins (A, C, and B complexes), omega-3 fatty acids, and the minerals calcium and phosphate, which are all essential nutrients. Milk contains about 750 calories per litre. Harley, John P

Breast milk contains approximately 3–5% of lipids, 98% of which are triacylglycerols (fats and oils), and they comprise an essential part of young infants’ diet. The key benefits that are provided to the baby by human milk fat (HMF) relate to


Energy: almost 50% of the energy required by the fast-growing young infant originates from fat.


Physical protection: a layer of stored body fat protects the infant against internal injuries while it starts to explore the world and it acts as an insulant to maintain body heat.


Development: HMF provides essential fatty acids required for healthy development of the brain function and visual development, it helps develop and support the immune system, and is an essential component of body tissues and many organs. Furthermore, its hydrophobic nature allows the absorption of fat-soluble vitamins (A, D, E, and K), and therefore HMF is a well-matched vehicle by which vitamins are provided to the infant. ?  R.P. Happe (2016).

The first fluid produced by mothers after delivery is colostrum, which is distinct in volume, appearance and composition. Colostrum, produced in low quantities in the first few days postpartum, is rich in immunologic components as well as developmental factors such as epidermal growth factor. Colostrum also contains relatively low concentrations of lactose, indicating its primary functions to be immunologic and trophic rather than nutritional. Levels of sodium, chloride and magnesium are higher and levels of potassium and calcium are lower in colostrum than later milk. As tight junction closure occurs in the mammary epithelium, the sodium to potassium ratio decreases and lactose concentration increases, indicating secretory activation and the creation of transitional milk. The timing of secretory activation (lactogenesis stage II) varies among women, but usually happens over the first few days postpartum. Delayed onset of lactogenesis is defined as onset >72 hours after delivery and appears to occur more often with preterm delivery and maternal obesity, and may be predicted by markers of metabolic health

Transitional milk shares some of the properties of colostrum but represents a period of “ramped up” milk production to support the nutritional and developmental needs of the rapidly growing infant, and typically occurs from 5 days to two weeks postpartum, after which milk is considered largely mature as described by R.P Happe (2016). By four to six weeks postpartum, human milk is considered fully mature. In contrast to the dramatic shift in composition observed in the first month of life, human milk remains relatively similar in composition, although subtle changes in milk composition do occur over the course of lactation.

Breast milk also has immunological properties and these are what make it unique. It contains a variety of antibodies, immune cells and other chemicals that ward off disease. The colostrum makes up for what it lacks in essential nutrients by, as John P (2015) writes, having higher concentrations of proteins and immunoprotective elements. The lymphocytes breastmilk carry can also destroy foreign micro-organisms outright. This helps with protecting the child against any pathogens that may invade its gastrointestinal system ensuring that it will always be able to take milk.

Table 1

Macronutrient (g/dL) and energy (kcal/dL) composition of human milk from specified references

Author (year), n





Mean (± 2 SD)

Mean (± 2 SD)

Mean (± 2 SD)

Mean (± 2 SD)

Term infants, 24-hour collection, mature milk

Nommsen et al (1991), n=58

1.2 (0.9, 1.5)

3.6 (2.2, 5.0)

7.4 (7.2, 7.7)

70 (57, 83)

Donor human milk samples

Wojcik et al (2009), n=415

1.2 (0.7, 1.7)

3.2 (1.2, 5.2)

7.8 (6.0, 9.6)

65 (43, 87)

Michaelsen et al (1990), n=2553

a 0.9 (0.6, 1.4)

a 3.6 (1.8, 8.9)

a 7.2 (6.4, 7.6)

a 67 (50,115)

Representative values of mature milk, term infants

Reference standard




65 to 70

Preterm, 24-hour collection, first 8 weeks of life

Bauer & Gerss (2011)



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