What Is Breast Milk Made Of?

What Is Breast Milk Made Of?

Last update: 23 October, 2017

Breast milk is unique and cannot be imitated. It changes composition according to babies’ age, needs, as well as the time of year. Do you know what breast milk is made of?

Nature is very wise. Breast milk has the exact components that the baby needs for development.

According to the World Health Organization, children receive good nutrition from breast milk up to the age of 3 as long as other foods are incorporated.

Breastfeeding also creates a bond of wonderful possibilities between mother and child – a loving relationship and a channel of dialogue between both. This is what is known as attachment.

Breastfeeding provides the emotional security for the beginning of life that every human being needs.


what is breast milk made of

How is breast milk produced?

First, the mother produces colostrum, a watery and yellowish substance rich in minerals and vitamins A, E, K and B12. It is very easy to digest and creates a laxative action, which helps to expel the feces produced in the child’s gut during gestation.

This colostrum is composed of leukocytes and antibodies, which are responsible for protecting the baby from possible intestinal and respiratory infections until his immune system develops.

A few days after delivery, there is an increase in milk itself, a substance low in protein but high in fats and carbohydrates.

At the beginning it is very light and at the end it becomes creamy. It is this change in texture that allows the newborn to first quench his thirst, and then his appetite.

What is breast milk made of?


It is the most abundant component of breast milk. It contributes to the newborn’s ability to regulate body temperature.

It has been shown that the needs of infants can be fully satisfied by the water in breast milk.


Many of the properties of human milk can be traced back to their unique proteins. 

Human milk is characterized by a predominance of whey proteins over casein. From a nutritional standpoint, casein not only fulfills functions as a protein, but fragments of it also form part of the bifidus factor, and others have immunomodulatory functions.

Lactoferrin is another major serum protein. It aids in the protection of the newborn against microorganisms.

This protein binds to iron and makes it so germs cannot replicate.

Immunoglobulins or antibodies are proteins capable of binding to and recognizing structures they are directed against. Recognizing the antigen allows the immune system to destroy it. They are very important for their protective effect.

When an immunologically mature infant consumes breast milk, it receives antibodies against environmental microorganisms to which it is exposed.


mother breastfeeding child

The main carbohydrate in milk is lactose. It is synthesized in the mammary gland.

Its main function is to provide energy, but it appears to be specific for the growth of the newborn since it has the following beneficial properties:

  • It facilitates the absorption of calcium
  • It is a source of galactose, which is essential for the production of galactoloipids, indispensable for the development of the central nervous system.
  • It influences volume control of the milk, regulating the transport of water.
  • It is part of the bifidus factor

Lactose levels are fairly constant in each mother’s milk throughout the day. Even in mothers with poor nutrition, lactose levels do not vary.


Fats and oils are an important source of energy and are essential for the development of the nervous system.

Fat is the most variable component of milk, increasing during the day and during feeding, with low values at the beginning and high levels at the end.

Over the course of intake, the watery phase of the milk is replaced with fat globules in increasing proportion.

Human milk provides fatty acids that are related to vision. It has been shown that formula-fed children have less visual acuity than those fed breast milk.

Mineral salts

A breastfed child handles water more easily, for temperature control through sweat, for example.

  • Sodium and potassium: potassium levels are much higher than those of sodium, similar to the proportion found in cells. Low levels of sodium and high levels of potassium in breast milk have a beneficial effect.
  • Iron: the rate of iron absorption of breast milk reaches 50% of available iron. Children exclusively breastfed for the first 6 months are much less likely to have the iron deficiency known as anemia.
  • Calcium: calcium and phosphorous levels are low in human milk but easily absorbed.
  • Zinc: breast milk contains biologically available zinc. Acrodermatitis enteropathica, a congenital alteration of zinc metabolism, does not occur in breastfed infants.


baby being breastfed

The water-soluble vitamins are ingested in proportions suitable for the infant.

  • Vitamin A. Vitamin A, like all fat-soluble vitamins (A, E, D and K) are transported in milk fat. The content is even higher in colostrum and in the milk of mothers of premature babies.
  • Vitamin D. The main source of vitamin D is sun exposure, not dietary intake. There are no deficiencies in exclusively breastfed children.
  • Vitamin E. Breast milk provides more than enough levels of vitamin E. Colostrum provides about 3 times more vitamin E than mature milk. This is important since infants have low reserves and need an adequate amount in the first days of life.
  • Vitamin K. The concentration of vitamin K is higher in colostrum and in transitional milk.

Some curiosities …

  • Breast milk is an aqueous suspension of nutrients, cells, hormones, growth factors and immunoglobulins that exert a complex interrelationship between the mother and her baby.
  • Milk varies with the time of day, over time throughout lactation, and also within the same period of intake.
  • All variations are functional. Human milk has the potential to adapt to the individual needs of each infant.

All cited sources were thoroughly reviewed by our team to ensure their quality, reliability, currency, and validity. The bibliography of this article was considered reliable and of academic or scientific accuracy.

This text is provided for informational purposes only and does not replace consultation with a professional. If in doubt, consult your specialist.