Composition Of Breast Milk – All You Need To Know

Composition Of Breast Milk – All You Need To Know

18 May 2022 | 4 min Read

Sayani Basu

Author | 497 Articles

Breast milk is produced by the mammary glands that are located in a woman’s breasts. Several health organisations around the world have recognised human breast milk as an ideal source of nutrition to support early life. 

In fact, the World Health Organisation (WHO) also recommends that a mother should breastfeed her baby exclusively for six months as breast milk is the ideal food for infants.

Containing antibodies that protect the infant against many common childhood illnesses, breast milk provides all the energy and nutrients that the infant needs. But do you know what’s in breast milk that makes it highly recommended?

Breast milk is full of minerals, vitamins and proteins that nourish and protect your little one. However, the composition of breast milk varies over time. Read on to find out what breast milk contains and how it changes to meet your baby’s needs.

Breast milk is an excellent source of nutrients for your baby. | Image Source: pexels

Composition Of Breast Milk

Breast milk is primarily composed of water, proteins, lipids, carbohydrates and other biologically active components. However, the composition changes over a single feed as well as over the period of lactation.

Macronutrient Composition

The macronutrient composition of the breast milk include:


Human breast milk is made up of about 90% of water. Water maintains hydration, helps regulate body temperature, lubricates joints, and protects all the organs.

Breast milk alone provides all the water required by the infants for survival.


Studies have shown that carbohydrates are a preferred energy source for the brain and the main carbohydrate in breast milk is milk sugar which is known as lactose. Human milk contains more lactose than cow’s milk.

Other carbohydrates found in breast milk are oligosaccharides that promote healthy bacteria in your baby’s intestines.

These bacteria protect your baby’s gut and help fight diseases like infant diarrhoea.

Lipids (Fats)

Lipids make up about 4% of breast milk and provide over half of the calories to your little one.

Lipids are a major source of energy, cholesterol, and essential fatty acids such as DHA and are necessary for the development of your baby’s brain, nervous system, and vision.

The high-calorie content of lipids is also responsible for the baby’s healthy weight gain.


Proteins build, strengthen, and repair the body’s tissue and make hormones, enzymes, and antibodies. The protein in breast milk is easy for the little ones to digest.

Lactoferrin is a form of protein in breast milk that moves iron through your baby’s body and protects your newborn’s intestines from infections.

Your breast milk contains antibodies that help to fight illness and disease in your baby. | Image Source: pexels


Bioactive Components

There are several elements of breast milk that are unique and are not found in formula milk. These are:

Immunoglobulins (Antibodies)

Immunoglobulins are antibodies that help to fight illness and disease. Due to these natural immune substances, breast milk can almost be thought of as a baby’s first vaccine.

It also helps protect against the common cold, ear infections, vomiting, diarrhoea, and other potentially dangerous infections.​

The primary antibody in breast milk is Secretory Immunoglobulin A (IgA) that coats the baby’s lungs and intestines, sealing them to prevent germs from entering the body and bloodstream.


Hormones involved in milk production include prolactin and thyroid hormones. These hormones also influence growth and development, metabolism, stress and pain responses, and blood pressure regulation.


Human breast milk contains several enzymes that aid digestion by breaking down fats or proteins. Some enzymes also provide immune support.


Breast milk also contains vitamins and minerals that are important for your infants health and development:


Vitamins found in breast milk support healthy bones, eyes, and skin and are necessary to prevent diseases of malnutrition like scurvy and rickets.


Breast milk is full of minerals that your baby’s body needs to be healthy and strong.

Minerals like iron, zinc, calcium, sodium, chloride, magnesium, and selenium build strong bones and produce red blood cells. These minerals also promote proper muscle and nerve function.

Key Takeaways

There are three phases of breast milk – colostrum, transitional milk and mature milk. Doctors refer to colostrum as “liquid gold” for its importance for your infant. As the composition of breast milk changes over time, the ratio and amounts of whey/ casein protein changes from colostrum to mature milk.

Between the two, whey protein is predominant and makes up to 50-80% of protein content in the breast milk. Thus, even if the composition of the breast milk changes, the protein composition of breast milk is dynamic.











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