10 magical facts about breast milk

During breastfeeding, breast milk is a rich source of Immunoglobulin A, anti-inflammatory factors, and immunologically active cells needed to induce both tolerance to non-harmful antigens (dietary antigens or beneficial commensal microbes) and to develop a robust immune defence against pathogenic organisms. This is known as the "entero-mammary pathway", which occurs when bacteria from the mother's gastrointestinal tract are translocated to the mammary glands via immune cells [1]. 

The production of Immunoglobulin A in infants is still very immature. This is why their presence in breast milk helps protect the baby in the meantime — a kind of "immune umbrella". Antibodies form a barrier that prevents most pathogens from binding to the cells of the mucous membranes and epidermis [2].

Immunoglobulins are present in high concentrations in colostrum, and even more so in mothers whose babies were born prematurely.

To find out more, read our article on breastfeeding and immunity.

When babies suckle, the diameter of the nipple increases and a vacuum is created by negative pressure, drawing in fluids including nasal and oral secretions, saliva and milk from the child's mouth into the milk ducts [3].

External bacteria can enter the mammary gland through " retrograde transfer " from sources such as the areolar skin or the infant's oral cavity. The reversal of milk flow towards the breast during feeding may allow microbes to enter and establish themselves in the milk ducts from the infant's mouth. This is known as 'retrograde milk flow' [4]. 

The mammary gland is filled with immune cells that end up in the milk, in order to protect against and respond to the pathogens that baby encounters [5].

During breastfeeding, the baby's saliva interacts with breast milk whilst simultaneously providing precursors to molecules that promote growth. Breast milk interacts via the enzyme Xanthine Oxidase with the newborn's saliva during feeding, producing peroxides (hydrogen peroxide) whose antimicrobial action has been demonstrated. This interaction is also thought to act as a kind of "natural selection" to favour beneficial bacteria, which subsequently colonise the gut.

Milk therefore plays more than a simple nutritional role in mammals, as it interacts with infant saliva to produce a powerful combination of stimulating and inhibitory metabolites that regulate the oral, and therefore intestinal, microbiota [6].

Breast milk contains prebiotics — more than 130 different oligosaccharides, the best known being Human Milk Oligosaccharides — which stimulate beneficial colonisation and reduce colonisation by pathogens in the colon [7].

It also contains Bifidobacteria, which produce organic acids and prevent the growth of pathogenic bacteria [8]. The longer breastfeeding continues, the greater the effects on the microbiome. 
A precious gift when you consider that "the microbiome is said to be "resilient", meaning that by around 2–3 years of age, it will not change much for the rest of life [9]!

In the first few days of life, your baby feeds frequently as they take in very small amounts at a time. They are learning to coordinate sucking, swallowing and breathing. Over time, they take in larger quantities of milk at a sustained frequency: roughly every 2 to 3 hours on average. 

However, they may start wanting to feed much more frequently, for various reasons (growth spurts, illness, etc.) [10] [11]. Cluster feeding is normal and you should not follow a strict breastfeeding schedule - feed your baby on demand and without watching the clock.

Melatonin, whose levels increase in your milk at night, will help your baby regulate their natural body clock [12].

In addition to melatonin, breast milk produced at night is rich in other substances such as tryptophan, an amino acid that promotes sleep. It is a precursor to serotonin, a hormone essential for the brain and its development. Tryptophan increases the number of serotonin receptors. A baby breastfed at night will therefore develop more serotonin receptors, as shown by Darcia Narvaez, an American researcher [13].

Find our article on breastfeeding and sleep for more information. 

The composition of breast milk varies according to how the feed progresses, throughout the day and over the course of the breastfeeding period.

At the start of a feed, breast milk is composed of a high proportion of water, lactose and minerals to quench thirst. As the feed progresses, the amounts of proteins and fats increase. Towards the end of each feed, fats become increasingly concentrated in the milk, giving the baby a feeling of fullness [14].

A baby fed on demand can adjust feeds according to their own needs. 

At birth, a baby's brain is only a quarter of its adult size. Babies need a continuous source of fuel to power their brain, which grows considerably in the first few months. They therefore need frequent nourishment.

Studies show that DHA, a fatty acid, is beneficial for the development of the baby's brain [15], language development and vision [16]. Studies even show that the concentration of DHA in breast milk can vary by a factor of 10 depending on your DHA intake dietary.

Maternal DHA levels decline during breastfeeding, which reflects the transfer into breast milk of a fatty acid that is important for the child's development. Studies even show that the concentration of DHA in breast milk can vary by a factor of 10 depending on your intake [17]! 

Did you know? The breastfeeding snack Cho-chocolat, the spread Crazy nut all contain 200 mg of DHA, which is the recommended amount. You can also take the supplement omega-3 pregnancy, with 200 mg of DHA per capsule, in addition to our postpartum food supplement to meet your nutritional needs. 

Breast milk contains stem cells, as does amniotic fluid [18].  

The presence of these cells can most likely be explained by the higher needs of newborns in terms of immune protection, growth, protein synthesis, neurocognitive development and blood vessel development [19]. 

#10 Babies recognise the smell of their mother's milk
 

Babies are born with very limited vision, and the world outside the womb is very stimulating and bright for them. Their sense of smell takes over from their vision, before their sight sharpens over time. The smell of breast milk is very similar to the smell of amniotic fluid, which explains its attractiveness to the newborn [20]. Orientation towards the scents of the mother's breast is an innate response in newborns [21].

Researchers have shown that newborns are very quickly able to distinguish the smell of their own mother's milk from that of another mother's milk. Breastfed newborns were able to distinguish their mother's scent from those produced by unfamiliar breastfeeding women [22].

This is why, given the importance of biological scents for newborns, products that eliminate or mask these signals should be avoided during the perinatal period [23].