What’s in breastmilk?
by Cordelia Uys, Breastfeeding Counsellor
December 2021
This article describes the nutrients and immunological factors in breastmilk.
Humans are mammals, which means it’s the biological norm for us to breastfeed our young. All mammals are capable of producing milk, but because different species have different needs and live in different environments, the proportion of nutrients in their milk are very different. For example, hooded seals live in the freezing cold coastal waters of the North Atlantic, and in order for their pups to survive, they need to drink up to 7 kilograms of milk fat per day. The pups only drink their mother’s milk for 4 days, which is why a hooded seal’s milk contains about 61% fat, 5% protein and 1% lactose.
Human infants require an extremely long period of parental care following birth, and they grow relatively slowly. So human milk contains approximately 3.6% fat, 1.2% protein, and 7.4% lactose (the main carbohydrate in breastmilk). Around 88% of breastmilk is water, which is why breastfed babies don’t need any additional water until they start solids.
Cow’s milk contains 3% to 4% fat, 3.5% protein and 5% lactose, and circa 87.5% of cow’s milk is water. There is more protein in cow’s milk because calves need to grow much faster than human babies, and there is more lactose in human milk because our brains need to grow much more than cows’ brains.
Breastmilk contains just the right balance of nutrients, such as fats, proteins, lactose, vitamins, minerals, and water. These provide the optimal nutritional, immunological, and emotional nurturing for an infant to grow and develop. Breastmilk plays a key role in children’s brain development. It is rich in omega-3 and omega-6 fatty acids, taurine, choline, zinc, and many other nutrients that support this process. It’s also recently been discovered that breastmilk contains stem cells, which are the building blocks for all other cells.
Immunological protections of breastmilk:
When a baby is born, their immune system is immature. It takes up to a year for a baby to start producing enough antibodies to protect him or herself from serious illnesses, and a child’s immune system isn’t fully developed until around the age of five. Every drop of breastmilk contains millions of white blood cells which are the same cells that circulate through our blood stream, destroying harmful viruses and bacteria. These cells help protect a baby from the illnesses their mother has experienced.
Breastmilk also contains infection-fighting proteins known as immunoglobulins. These are like natural antibiotics which act against any harmful germs that the baby is exposed to.
Immunoglobulins also allow beneficial bacteria in the digestive system to flourish. The growth of friendly bacteria gives a baby’s stomach the defence needed to fight off harmful organisms and promote a healthy digestive system. There are known to be approximately 200 structurally different oligosaccharides (a type of carbohydrate) in breastmilk, the majority of which can’t be digested by the baby and are there just to feed the good bacteria in the baby’s gut. Breastmilk even protects against parasites. Many nutrients in breastmilk cannot be replicated artificially.
Breastmilk also contains natural painkillers called endocannabinoids, as well as tryptophan, which is the building block for hormones that induce and regulate sleep.
The infection fighting properties in a mother’s milk are being continually updated in response to the mother’s environment. When she encounters a new germ, her mature immune system will deploy some white blood cells to fight it off and quickly pass them on to her baby through her milk. And whenever her baby picks up an infection, the thin skin of a mother’s areola allows germs in the baby’s saliva to pass directly into the mother’s blood stream. Her immune system kicks in, manufactures several billion white blood cells, which pass back to the baby at the next feed. This means that if a mother and her baby are sitting on a bus and someone sneezes on them, within hours, the mother’s body will be making antibodies to the germs in that sneeze, and delivering them to her baby via her breastmilk. Some of the immune factors in breastmilk increase in concentration when solids are introduced, and during the second year of a child’s life.
According to the Lancet Breastfeeding Series 2016, breastmilk is ‘exquisitely personalised medicine’.
UNICEF and the World Health Organization recommend exclusive breastfeeding for 6 months, and continued breastfeeding, alongside the introduction of solid food, up to and beyond two years. A child will continue to receive immunological protection from their mother’s milk for as long as they are receiving any breastmilk.
What’s in breastmilk that isn’t in infant formula (From Why Formula Feeding Matters by Shel Banks):
There are many things which are present in breastmilk that are not present in our ‘breastmilk substitutes’. These include stem cells, enzymes, growth factors, hormones, anti-inflammatory compounds, live ‘friendly’ bacteria which colonise the gut and help with digestion and health, live viral fragments that trigger protective antibody responses and so on. And since these ingredients in human milk are human, they are very unlikely to trigger allergic responses in human babies.
Links:
https://www.breastfeeding.asn.au/bfinfo/breastmilk-composition
http://www.human-milk.com/infographic/leaflet.html
https://kellymom.com/pregnancy/bf-prep/how_breastmilk_protects_newborns/
http://www.fao.org/dairy-production-products/products/milk-composition/en/
https://www.nytimes.com/2019/06/12/health/breastmilk-microbiome-parenting.html
https://www.llli.org/breast-milks-circadian-rhythms-2/