As the main carbohydrate in breast milk, lactose provides a large proportion of energy and calories to the baby. At the same time, it helps to absorb minerals and supports the baby’s immune system.
The high energy or caloric requirements regarding baby nutrition are also met with the help of special lipids in breast milk. These ensure a proper physiological, neurological, and immunological development. In addition, lipids introduce taste and aroma to breast milk. As a positive side-effect, breast milk has taste and aroma.
A prebiotic is "a substrate that is selectively utilized by host microorganisms conferring a health benefit" (Gibson et al. 2017).
Milk proteins can be divided into caseins, whey proteins, and milk fat globule membranes (MFGMs). They have a positive effect on digestion as well as the absorption of micronutrients.
Breast milk contains a variety of vitamins and minerals, which are important for child development. While some tendencies in concentrations exist, the actual vitamin and mineral supply also depends on the breastfeeding mother’s diet.
Nucleotides such as deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are involved in several biochemical processes essential for a living body. Moreover, nucleotides available in breast milk have also been shown to provide several beneficial biological effects for the baby.
Breast milk contains a number of viable bacteria – probiotics – which have the power to provide health benefits to the baby. These positive health effects do not only impact the well-being of the baby at the time of breastfeeding but may also affect health in later stages of life.
Lactose is the main and most abundant carbohydrate in breast milk. It is a disaccharide molecule consisting of glucose bound to galactose, generally regarded as the main sugar in breast milk. The concentration of lactose is fairly constant in the mother’s milk, and accounts for 40% of total milk energy or calories (Guo, 2014). Stable concentration of lactose is important to maintain constant osmotic pressure in breast milk. Lactose promotes the absorption of minerals such as calcium or magnesium (Martin et al, 2016). It is also suggested that lactose enhances the infant’s immune system by upregulating antimicrobial peptides (AMPs) associated with protection and regulation of infantile microbiota (Cederlund et al, 2013).back
Lipids are key nutrients available in breast milk. Milk is rich in lipids to meet the high energy or caloric requirements of babies, but lipids also provide taste and aroma (Martin et al, 2016). Triglycerides are the main constituents of lipids in breast milk and they account for 95% of the breast milk’s total composition. Breast milk contains the essential fatty acids linoleic acid (LA) and α-linoleic acid (ALA), and special lipids such as long-chain polyunsaturated fatty acids (LC-PUFAs) which provide distinct benefits during babies’ early development. The two essential fatty acids are converted into arachidonic acid (AA) and eicosapentaenoic acid (EPA), the latter being converted into docosahexaenoic acid (DHA). EPA and DHA are important for growth regulation, immune function, inflammatory responses, and cognitive and motor development in newborns (Martin et al, 2016). LC-PUFAs, including DHA and AA, are essential for cell differentiation and promoting healthy neurological and immune system development during the perinatal period (Koletzo et al, 2001).back
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Milk proteins can be divided into caseins, whey proteins, and milk fat globule membranes proteins (MFGM proteins) (Lopez Alvarez, 2007). Since MFGM proteins simply enclose the lipid globules in milk, they only represent a small amount of breast milk proteins. Casein and whey proteins account for a greater percentage, but their actual concentration is hard to identify because it changes and adapts according to the specific needs of the baby. In general, milk proteins are important to supply amino acids, and support digestion and absorption of micronutrients such as vitamins (Lönnerdal, 2003).back
Breast milk contains a variety of vitamins (including vitamins A, B6 and B12) in adequate quantities to stimulate healthy growth of the baby. As micronutrients are passed on to the baby via lactation, their profile is highly dependent on maternal diet. Nonetheless, the concentrations of vitamins D and K are typically low, necessitating postnatal supplementation of these vitamins (Ballard et al, 2013). Minerals such as iodine influence a variety of physiological effects and are cofactors for several different metabolic pathways, proving to be essential for healthy baby development (Martin et al, 2016).back
Nucleotides are present in human milk and represent 2-5% of total non-protein nitrogen (Cosgrove, 1998; Thorell et al, 1996). Nucleotides are organic substances that serve as monomer units or building blocks for the formation of nucleic acids – a purine (adenine or guanine) or pyrimidine (cytosine, uracil, or thymine) base, linked to a pentose sugar and esterified with a phosphoric acid. Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are the two types of nucleic acids that occur in nature and are essential to all life-forms. They participate in several biochemical pathways which are vital for a living body, including being or taking part in: i) monomer units of DNA and RNA; ii) biosynthesis processes (e.g. the glycogenesis process); iii) co-enzyme components; iv) biological regulators; and v) the generation of the energy source in biological systems – adenosine triphosphate (ATP) (Lerner et al, 2000). Due to their availability in breast milk composition, they have also been evaluated for numerous biological effects on infants. These effects include intestinal growth and differentiation, intestinal repair, immune function, and even absorption of minerals such as iron (Lerner et al, 2000).back
Probiotics are viable bacteria present in breast milk which provide benefits to the host when administered in certain quantities (Guarner et al, 2017). Bacterial gut colonisation in early life is a process that exerts influence on the health status of an infant. A recent study shows that breast milk is a source of live staphylococci, streptococci, lactic acid bacteria, bifidobacteria, propionibacteria, corynebacteria, and closely related Gram-positive bacteria to the infant gut (Fernández et al, 2013). Other studies show that there is also a mother-infant transfer of bacterial strains which include Lactobacillus, Staphylococcus, Enterococcus, and Bifidobacterium (Soto et al, 2014). By consuming approximately 800ml/day of milk, breastfed infants can ingest between 105 to 107 beneficial bacteria (Heikkilä et al, 2003). The exposure of infants to breast milk may even provide beneficial effects later in life or prevent future health problems (Soto et al, 2014). More detailed information is provided under the section NaturScience.back