The breast milk is the best nutrition for baby. Its specific composition covers all the needs of baby and is perfectly adapted to its development . It contains the vitamins, minerals, trace elements, sugars, fats, proteins that your baby needs to grow well, all in just quantities .
But that’s not all, its composition varies during the feeding , getting rich in fat as the breast is empty or when the feeds approach, but also during the day and over months to really adapt to the needs of growing baby.
Composition of breast milk
(Hamosh 2001, Jensen 1995, Neville 2001, Picciano 2001a and 2001b, 1993)
Proteins and nitrogenous substances
The protein content of women’s milk, between 8 and 12 g / L, is much lower than that of other mammals.Nevertheless, it is perfectly adapted to the needs of the infant because of an excellent absorption and a perfect adequation amino acid profile.Proteins in women’s milk are also very specific; even caseins, which account for only 40% of proteins (as opposed to 80% in cow’s milk) are different. Casein from woman’s milk forms micelles much smaller than those of cow’s milk. It is mainly casein – the hydrolysis of which leads to peptides (caséomorphines) with opioid properties and casein – highly glycosylated, whose C terminal fraction has bifidogenic effects. Finally, a high percentage of protein (60%) does not precipitate with caseins; they are called “soluble proteins”.
This high percentage of soluble proteins and small casein micelles explain the finer coagulation of the woman’s milk in the infant’s stomach, contributing to faster gastric emptying. Among these soluble proteins, some have an essential functional role such as immunoglobulins, in particular secretory IgA (IgAs) (0.5 to 1 g / L), lactoferrins, lysozyme, beta-defensin 1, enzymes (in particular lipase), growth factors such as Insulin-like Growth Factor (IGF1), Transforming Growth Factor (TGF), leukocyte growth factors (G-CSF) and Epidermal Growth Factor (EGF) , which has a trophic action on the gastric and intestinal mucosa.Orythropoietin, folate binding proteins, vitamins B12 and D are also found,
Woman’s milk is therefore not a simple “vehicle” of nutrients; It has many biological properties. Besides proteins, the sum of peptides, free amino acids (including taurine), urea, uric acid, sugars and amino alcohols, polyamines, nucleotides, and carnitine, represents 20 to 25% of the total nitrogen of milk, while it constitutes only 3 to 5% of this nitrogen in cow’s milk.
Lipids and digestibility of fats
If the lipid content (35 g / L on average) is close to that of cow’s milk, the digestibility and the absorption coefficient of fat of women’s milk are much higher (80% against 60% in the first days, rapidly reaching 95% against 80% at 3 months for cow’s milk). The best digestibility of fat is the presence in the woman’s milk of a bile acid dependent lipase of the newborn which compensates, at the duodenal level, insufficiency of pancreatic lipases; the different structure of the triglycerides is added: 70% of the palmitic acid (25% of the total fatty acids) being in position 2 on the glycerol, it is well absorbed in the form of monoglyceride which is not the case with cow’s milk.Woman’s milk is high in cholesterol (2.6 to 3,
Cholesterolemia is higher in breastfed infants. We must remember the role of cholesterol in the structure of membranes, as a precursor hormone and in brain development. The woman’s milk contains polyunsaturated fatty acids (PUFAs), essential fatty acids but also their higher homologues, in particular arachidonic acid. (AA: 0.46 g / 100 g of fatty acids) in the linoleic (n-6) and docosahexaenoic acid (DHA: 0.25 g / 100 g fatty acids) series in the _-linolenic series (n -3). This content depends on the dietary intake of n-6 and n-3 fatty acids of the lactating woman (Heird, 2000). AA and DHA have a demonstrated role in the processes of brain and retinal maturation.
The immaturity in the premature of the processes of elongation and especially of desaturation which allow their synthesis starting from the two essential fatty acids led to a consensus on the necessity of a specific and balanced supplementation in AA and DHA of the premature preparations .
Carbohydrates and Oligosaccharides
Milks Overall, mature women’s milk contains 75 g / L of carbohydrates, including 63 g of lactose and 12 g of oligosaccharides, while cow’s milk contains only lactose.Formed of five sugars elemental (glucose, galactose, N-acetylglucosamine, fucose, sialic acid), of branched structure, oligosaccharides constitute a major originality of women’s milk: they are more than 130 in number and constitute true prebiotics.
Not digestible in the small intestine, with the exception of sialic acid which can be cleaved and then absorbed, they play an essential role in the establishment of the bacterial colic-dominated in children in the breast, by the Bifidobacteria, especially Bifidobacterium bifidum.The role of these oligosaccharides (almost absent from cow’s milk) in the protection against digestive infections, but also extra-digestive, is now well argued (Kunz, 2000).
Other components of female milk
The relatively low content of nitrogen and mineral salts (2.50 g / L) makes it possible to limit the osmolar renal load to rather low values (93 mOsm / L), whereas it is much more high for cow’s milk (308 mOsm / L). This low osmolar renal load constitutes a safety in the event of excessive water losses, by transpiration or diarrhea, by making it possible to better ensure the equilibrium maintenance of the hydro-mineral balance. Another important point concerns the better bioavailability of various trace elements like iron and zinc, because of the ligands present in the woman’s milk, which facilitate their absorption.
During the first three days of breastfeeding, breast’s milk, then called , has a different composition of mature milk. Less rich in lipids and lactose, it has a lower energy density (450-480 against 650-700 kcal / L); on the other hand, it is richer in immuno-competent cells (10 times more), in oligosaccharides (22 to 24 versus 12 to 13 g / L), and in proteins (22 versus 11 g / L). The increase concerns functional soluble proteins such as immunoglobulins, in particular IgAs, lactoferrins, various growth factors (G-CSF, EGF, IGF1), the different cytokines, whereas caseins are practically absent.
All of these help to protect the newborn who is particularly vulnerable to infection. In a few days, the composition joins that of mature milk. The milk of women who give birth prematurely is richer in PUFA ( Polyunsaturated Fatty Acids), which corresponds to the higher needs of premature infants in these PUFAs for cerebral maturation. In the course of the head, the composition of the milk changes and is enriched with fats and micelles of casein. The analysis of an isolated sample of milk is therefore meaningless and could lead to the mistaken belief that the caloric density of milk is insufficient, while it remains normal, even when the mother is malnourished. Variations in maternal nutrition may, however, affect milk fatty acid composition, iodine, selenium, vitamin A, and B-group vitamins.