Home Breastfeeding Breast Milk Composition: Macronutrients, Micronutrients & Growth Factors

Breast Milk Composition: Macronutrients, Micronutrients & Growth Factors

by Pooja Saini

Breast milk or the golden liquid is the gift of nature for the newborn baby and it is every mother’s duty to breastfeed the baby. According to the World Health Organization (WHO), infants should be exclusively breastfed for their first 6 months of life and it should be continued for 1-2 years.

Human breast milk contains various nutrients and bioactive factors that promote the healthy development of the baby. Besides this, exclusive breastfeeding reduces the risk of diseases and disorders even in adulthood.

Breast milk has a wonderful chemical makeup, which makes it so nutritious for the newborn. The composition of breast milk changes in response to many factors, matching the infant’s requirements according to its age and other characteristics, reports a study.

Therefore, it is believed that the composition of breast milk is specifically tailored by each mother to precisely reflect the requirements of her infant.

Maternal Diet may affect the Composition of Breast Milk

It is very well-known that maternal diet may affect the taste of the breast milk, but it does influence the composition too. Therefore, mothers must focus on eating a wholesome and nutritious diet.

Different food groups should be included in the mother’s diet so that her body gets a variety of nutrients. This will benefit the mother as well as the baby’s health.

Intake of high amounts of caffeine and chocolates should be limited, whereas trans-fat, alcohol intake and cigarette smoking should be avoided.

Eating an unhealthy, processed and imbalanced diet can affect the nutrient composition of the breast milk. This can have a negative impact on the infant’s health and the risk of deficiencies in infants may increase.

Breast Milk Composition

Breastfeeding Benefits for Women

The composition of breastmilk is discussed underneath:


The concentration of macronutrients in the human breast milk depends upon:

  1. Maternal body weight for height.
  2. Intake of protein.
  3. Return of menstruation.
  4. The frequency of nursing.

Let us have a look at the carbohydrate, protein and fatty acid composition of the breast milk:


Amino acids are the building blocks of the body and they are vital for infant growth and development. One study reported that the protein content of breast milk is approximately 1.4-1.6 grams/100 ml during early lactation, 0.8-1 grams/100 ml by 3-4 months of lactation and 0.7-0.8 grams/100 ml after 6 months of lactation.

However, maternal protein intake may have an impact on the protein content of the breast milk. Amino acids from breast milk facilitate digestion by enhancing the uptake of other nutrients. It further boosts the infant’s immune system and fights off bacterial and fungal infections.

A study found that poorly nourished mothers secreted milk low in certain amino acids. The reason behind this was a poor protein quality in the diet of the mothers.

Another interesting research found that the levels of some amino acids like lysine, threonine and valine in breast milk were low if the maternal diet is low in animal protein and soy protein. Soy is an inexpensive source of plant protein and it contains adequate quantities of essential amino acids too.

Therefore, eating a well-balanced and protein-rich diet will improve the composition of amino acids in breast milk.

The proteins of human milk are divided into casein fraction and whey fraction. The most abundant proteins in breast milk are:

  • Casein
  • Lactoferrin
  • Immunoglobulin A
  • Albumin
  • Lysozyme

The levels of protein decrease in the breast milk over the first 4 to 6 weeks.

Fatty Acid Composition

Fat is the most highly variable macronutrient of the breast milk. Hindmilk or the last milk of the feed may contain 2 to 3 times more concentration of fat as compared to the initial milk of a feed. 100 ml of the breast milk provides 65 calories. Almost 50% of these calories supplied to the infant comes from fat.

Intake of long-chain polyunsaturated fatty acid like DHA from diet or supplements has a positive impact on an infant’s brain development and vision.

Studies have reported that maternal diet influences the fatty acid composition of the breast milk. For example- in regions where the consumption of fish is high, the DHA content of breast milk was higher. The fat content of 100 ml of breast milk is approximately 3.8-4 grams.

Breastfeeding Benefits for Baby


The main sugar present in human breast milk is lactose. Of all the macronutrients present in human milk, lactose is the least variable. However, higher concentrations of lactose are found in the milk of mothers producing higher quantities of milk.

Besides this, the other significant carbohydrate present in breast milk is an oligosaccharide. Oligosaccharides have prebiotic effects that promote gut colonization.

They are a great immune booster, which blocks the adhesion of harmful pathogens to the cell surfaces. Thus, oligosaccharides strengthen the immune system and protect the infants against bacterial and viral infections.

Oligosaccharides are added to infant formulas, but they are different from human milk oligosaccharides and are not functionally equivalent.


The maternal diet and body stores may influence the micronutrient composition of the breast milk. Vitamins and minerals present in breast milk include:

  • Vitamin A
  • Thiamin or vitamin B1
  • Riboflavin or vitamin B2
  • Pyridoxine or vitamin B6
  • Cobalamin or vitamin B12
  • Vitamin D
  • Iodine
  • Iron
  • Copper
  • Zinc

The maternal diet may not always be optimal. Therefore, intake of multivitamin supplements is recommended during lactation.

The concentration of vitamin K is poor in breast milk. Hence, infants should receive vitamin K injections to avoid hemorrhagic disease of the newborn if required and advised by a doctor.

Low maternal exposure to sunshine, results in a low quantity of vitamin D in the breast milk. This has become a common and a huge problem among the populations worldwide. Thus, vitamin D supplementation is highly recommended to prevent vitamin D deficiency.

Bioactive Components

Bioactive components are those, which have a positive impact on the overall health. Human breast milk is loaded with numerous bioactive components that boost the good health of the infant.

Some of these components are naturally secreted by the cells of the mammary epithelium and others are produced by the cells carried within the milk. Whereas, others are drawn from the maternal serum.

These bioactive components not only provide nutrition, but they possess medicinal properties that promote infant survival and health.

Immunoglobulins present in breast milk are antibodies or a natural vaccine that boosts the immune system and protects the infant against bacteria, viruses and other harmful foreign bodies.

Such immune properties of breast milk may protect the infants against gastrointestinal infections, ear infections and the common cold, which can have a negative impact on the overall health.

Human Breast Milk

Other Factors in Breast Milk

There are several growth factors are present in breast milk.

Growth Factors

Breast milk contains growth factors that enhance growth, development and healing. These include:

Epidermal growth factor (EGF)

EGF is found in the breast milk, which is responsible for the maturation and healing of the intestinal mucosa. It reduces inflammation and protects the cells against damage.

Neuronal growth factor

It increases neuron survival and outgrowth.

Insulin-like growth factor

It increases tissue growth and stimulates erythropoiesis.

Vascular endothelial growth factor

It regulates the vascular system and the concentration of this factor is high in the colostrum.


Human breast milk contains significant amounts of erythropoietin that is responsible for increasing the red blood cells. Blood loss and immaturity of the hematopoietic system may contribute to anemia, which can impact the growth and development. Erythropoietin prevents anemia and increases the production of red blood cells.

Factors Affecting Human Milk Composition

The composition of human breast milk is dynamic and variable, unlike infant formulas, which are standardized within a narrow range of composition.

The two major factors that affect the composition of human milk are the stage of lactation and preterm delivery.

  • Preterm milk or milk of the mothers who give birth prematurely may differ than milk produced by women after full-term delivery.
  • The level of lactoferrin is higher in the preterm than in full-term Lactoferrin is a protein with bacteria-killing properties. The immune system of premature babies is not fully matured. Hence, they are at a higher risk of acquiring infections. That is why lactoferrin levels may be higher in preterm milk.
  • Besides this, studies have found that the concentration of energy, carbohydrates, proteins and fat in preterm milk is higher.
  • In case of extremely preterm milk (less than 28 weeks), the protein content is significantly higher.
  • Colostrum or the first fluid produced by the mothers after delivery is rich in immunologic components and growth factors. Whereas, the concentration of lactose, lipids and energy is low. This indicates that the primary function of the first fluid is to enhance the immunity rather than nutritional.
  • The fat concentration of breast milk is lower in the night and morning feedings, as compared to the afternoon and evening feedings.
  • Mothers who are overweight have a lower milk protein composition as compared to mothers who are not overweight.
  • The breast milk of mothers who smoke has a lower concentration of fat, proteins and immunoglobulins.
  • Maternal diet and body stores have a direct impact on the composition of vitamins and trace minerals in breast milk.
  • If the breast milk is stored, frozen or thawed, the levels of fat, lactoferrin and immunoglobulins may decrease.


Human breast milk is a valuable gift for the infant and it is every mother’s duty to breastfeed her little one. Breastfeeding provides two-sided benefits, that is, it is advantageous for the baby as well as the mother.

The composition of breast milk is such that it fulfills all the nutritional requirements of the baby. Breast milk is a highly nutritious liquid, which provides health benefits to the baby lifelong. The composition of the breastfeed changes to match the needs of the growing baby.

Hence, women must focus on their diet during the period of lactation and breastfeed exclusively for the first 6 months because breast milk is the sole source of nutrition for your little one.


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  3. Zhang Z, Adelman AS, Rai D, Boettcher J, Lőnnerdal B. Amino Acid Profiles in Term and Preterm Human Milk through Lactation: A Systematic Review. Nutrients. 2013; 5(12):4800-4821. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3875913/)
  4. Martin CR, Ling P-R, Blackburn GL. Review of Infant Feeding: Key Features of Breast Milk and Infant Formula. Nutrients. 2016; 8(5):279. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4882692/)
  5. Kim H, Kang S, Jung BM, Yi H, Jung JA, Chang N. Breast milk fatty acid composition and fatty acid intake of lactating mothers in South Korea. Br J Nutr. 2017 Feb;117(4):556-561. (https://www.ncbi.nlm.nih.gov/pubmed/28285609)
  6. Kelishadi R, Hadi B, Iranpour R, Khosravi-Darani K, Mirmoghtadaee P, Farajian S, Poursafa P. A study on lipid content and fatty acid of breast milk and its association with mother’s diet composition. J Res Med Sci. 2012 Sep;17(9):824-7. (https://www.ncbi.nlm.nih.gov/pubmed/23826007)
  7. Jantscher-Krenn E, Bode L. Human milk oligosaccharides and their potential benefits for the breast-fed neonate. Minerva Pediatr. 2012 (https://www.ncbi.nlm.nih.gov/pubmed/22350049)

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