Table 1.
Summary of breast milk main nutritional and immunological components
| Breast milk components |
Types and concentrations | Suggested role in infants’ growth |
|---|---|---|
| Immune cells (Andreas et al., 2015) | Macrophages (55–60%), neutrophils (30–40%), and lymphocytes T and B (5–10%) are found in human milk | • Help the infant develop a functional immune system through childhood. • The infant’s T-cell activity is stimulated by the help of macrophages which provide adequate protection against pathogens. |
| Cytokines (Murphy et al., 2018, Garofalo, 2010) | Interleukin-1 beta (IL-1b), IL-6, tumor necrosis factor-alpha (TNF-a), interferon-g (IFN-g), IL-10, transforming growth factor-beta (TGF-b) | • IL-1b pro-inflammatory cytokine is involved in the host defense response to injury and recruitment of neutrophils to the mammary gland. • IL-6 pro-inflammatory cytokine has an essential role in the development of the infant’s mucosal immunity. • Tumor necrosis factor-alpha (TNF-a), an important regulator of immune cells, is involved in the chemotactic activity of neutrophils and stimulates human milk’s IL-6 production. • TGF-b has been associated along with IL-6 and IL-10 in the development and differentiation of immunoglobulin A (IgA) producing cells in the mammary gland. It has also been linked with the maturation of the intestinal immune system as well as preventing allergic reactions. • Interferon-g (IFN-g), a cytokine with immuno-stimulatory and immuno-modulatory effects, is also capable of inhibiting virus replication. |
| Colony-stimulating factors (Gilmore et al., 1994) | Granulocyte-colony-stimulating factor (G-CSF), macrophage-colony-stimulating factor (M-CSF), and granulocyte-macrophage-colony-stimulating factor (GM-CSF) | Play a significant role in fetal intestinal development as well as having a beneficial effect on the proliferation, differentiation, and survival of neutrophils. |
| Immunoglobulins (Andreas et al., 2015) | Human breast milk is rich in immunoglobulins (IgA, IgM, and IgG), the most prominent of which is the secretory immunoglobulin A (sIgA) | Protect the infant at the mucosal level by interrupting virus replication, activating the complement system, and promoting phagocytosis. |
| Lactoferrin (Andreas et al., 2015) | A protein with antioxidant, bacteriostatic, and bactericidal properties | • Regulating immune and inflammatory responses. • Efficient in killing many different pathogens without inducing inflammation. |
| Oligosaccharides (Andreas et al., 2015) | The third largest component in breast milk, accounting for 12.9 g/L on average in mature milk and 20.9 g/L at four days postpartum | They act as prebiotics stimulating the proliferation of beneficial bacteria such as Bifidobacterium infantis in the intestines of infants essential for the enhancement of the intestine defense mechanisms against various pathogens. |
| Lipids (Andreas et al., 2015) | One of the major nutritional components of human milk is considered the major source of energy in human milk representing 40–55% of its overall energy. | Essential for central nervous system myelination due to the presence of Sphingomyelins which exist in the membrane of the milk fat globule |
| Polyunsaturated fatty acids (PUFAs) (Andreas et al., 2015) | Human milk is particularly rich in EFAs, GLA, DGLA, AA, EPA, and DHA. | DHA, EPA, and AA are the major LCPUFAs found in the brain and retina. Throughout childhood, neurological and immunological developments rely on the action of these fatty acids. It has been demonstrated that they also play a major role in the brain’s growth spurt occurring from the last trimester of pregnancy to age of 2. |
EFAs, essential fatty acids; GLA, gamma-linolenic acid; DGLA, dihomo-gamma-linolenic acid; AA, arachidonic Acid; EPA, eicosapentaenoic acid; DHA, docosahexaenoic acid; LCPUFAs, long-chain polyunsaturated fatty acids.