Breast Milk Proteins - Growth and Development

The magic of breast milk proteins that boost your baby’s growth and development

There is nothing like breast milk to provide power-packed nutrition to your baby for the first 6 months after birth. This milk is a wholesome food containing a complex mix of several nutrients in sufficient quantities and in balanced proportions to support the growth and development of infants. Breast milk is also easy to digest and protects your child against several allergies and infections. So, find out more about its composition, protein content, and how the proteins help your little one to grow and develop well.

Composition of breast milk:

Breast milk comprises the following principal elements:

  • Water - 87%
  • Protein - 0.9% to 1.0%
  • Fats - 3.5 to 4.5%
  • Carbohydrates - 7%
  • Oligosaccharides - 1% to 2.4%
  • Mineral constituents - 0.2%

Apart from these, breast milk also contains a sufficient quantity of vitamins and minerals, elements that boost immunity, lipase, and growth factors. Immunity-boosting elements in breast milk protect your baby against many common infections. Bile-salt stimulated lipase helps your child to digest fats and the epidermal growth factor facilitates the maturation of your child’s intestinal linings.

Types of breast milk protein

The protein composition of breast milk is around 1%, which is lower than the amount of protein found in the milk of animals. Cow’s milk has a protein content of around 3.5% for example. However, high protein content is not ideal, as it can exert pressure on your baby’s kidneys, which are not fully developed yet. The proteins you will find in breast milk are:

  •  Casein - Breast milk contains some amount of this protein, which forms curds. It is soft and easily digestible. 
  •  Whey protein - Around 50- 80% of breast milk is composed of whey protein. It is soluble, remains in the liquid state, and is easily digestible. 
  • Lysozyme - It is an enzymatic protein that is present in breast milk.
  •   Oligosaccharides - They are present in large quantities (ranging from 10 to 20 g/L) in breast milk. These are complex elements that help in the development of your child’s gut bacteria and the immune system. 
  •  Immunomodulating agents - These include immunoglobulin A, anti-inflammatory cytokines haptocorrin and lactoferrin. 

How does breast milk protein help your child to grow and develop?

Protein in breast milk provides amino acids that are important for your infant’s growth and development. Here is a detailed look at how each protein helps:

Casein – It helps in the formation of peptide protein during digestion, and enhances the solubility of calcium and zinc, and makes them available for various bodily functions.

Glutamine – This protein facilitates the citric acid cycle and is the main source of energy for the intestinal cells. It acts as a neurotransmitter in the brain too.

Alpha-lactalbumin - It is essential for the formation of lactose and is required for the binding of calcium and zinc ions.

Lactoferrin – This is a protein that helps prevent the spread of disease-causing bacteria, thereby preventing illnesses in infants. It modulates your child’s immune functions and responses as well.

Lysozyme – Like lactoferrin, it helps prevent the spread of disease-causing bacteria.

Haptocorrin – This is a protein that promotes the absorption of vitamin B12.

Immunoglobulin A antibody – It offers immune-protection and helps in the destruction of disease-causing bacteria, thereby protecting the mucosal surface of your child’s gut.

Composition of breast milk depends on lactation phases

Milk formation in the breasts can occur in two phases or stages. The initial phase is referred to as the transitional stage and is characterised by the production of colostrum, whereas, the latter phase is called the mature stage, where mature milk is produced.


Colostrum is yellowish and is produced by the breasts in the initial 2-3 days and up to 5 days after the birth of your child. It is usually secreted in small quantities (40-50 ml). Colostrum passes on immune protection to your child in the first few days of his or her life. It is rich in vitamin A, which is essential for the development and protection of your child’s eyes. It also contains epidermal growth factor that prepares your child’s gut lining to receive nutrients in the milk.

Colostrum is rich in several cells that help build your child’s immunity, such as macrophages and lymphocytes. Moreover, it contains larger quantities of protein, minerals and fat-soluble vitamins (A, E and K) compared to mature milk, which is formed at later stages.

To wrap up

So, you now know how breast milk provides a variety of proteins and other nutrients to support the growth as well as vital functions in your baby. Breast milk is also ideal for preterm babies and it has a sufficient quantity of protein, sodium, chloride, and potassium to meet your preterm child’s nutritional requirements. The composition of breast milk changes based on your baby’s age and needs. So, talk to your doctor to understand more about proteins found in breast milk and why breastfeeding is essential for the first 6 months.