Breast Milk Composition: Nutrients and Bioactive Factors

Composition of breast milk

Breast milk is one of the best milk which can help babies to grow properly, get all the nutrients they need, and stay healthy through development. Many doctors recommend women to breastfeed their babies until they are six months old and to add solid foods and breast milk in their diets till the age of 2. Breast milk is rich in nutrients that feed and protect your baby. The breast composition can vary over time. Breast milk includes the basic essential nutrients, such as fats, protein, and carbohydrates, as well as water to keep your baby hydrated. [1,2]

But, breast milk is not ordinary food. It has more value than nutrition alone. When six months have passed, you may be wondering what will happen with your breast milk. You sure ask yourself if your body will keep producing such high–quality mature milk for months and months or even years. You will start introducing solid foods at six months to bolster your baby’s stores of certain nutrients, such as iron but your breast milk will stay a big part of his or her diet [1,2]. When your baby will be seven months old, then he or she will be getting 93% of his or her calories from breast milk.

Even when your baby will be between 11 and 16 months old, around half of his or her daily calorie intake will be in milk form. So, you should enjoy the health benefits of your breast milk which you can give to your little one. Breast milk has many different bioactive components which can help with the development of the brain, immune system, and gastrointestinal tract.

Also, studies have shown that breast milk can reduce metabolic disease risk later in life. This also includes type 2 diabetes and obesity [3,4]. But, you should know that the composition of your breast milk changes as your baby develops.

Breast milk in comparison with infant formula:

composition of breast milk

The woman’s body is producing breast milk to meet the nutritional needs of her baby. It has everything that a baby needs to have proper growth and development and it changes in response to the baby’s needs. Breast milk is a complete source of nutrition and hydration. Also, it can help to protect the baby from getting sick through antibodies that pass from mother to baby through the milk. Breast milk is composed of hundreds of distinct bioactive molecules. Some of them are not yet fully understood by scientists.

Also, the infant formula provides complete nutrition, but it does not fully replicate the immune benefits of breast milk. But, infant formula is a safe and acceptable alternative to breast milk. For those parents who do not have breast milk to offer or for women who prefer not to breastfeed, they can give infant formula to their babies as a suitable option. One of the most important things to do for parents is to be sure that their babies are taking enough nutrients, no matter if it is through breast milk or through infant formula.

Macronutrient composition:

Primarily, breast milk is composed of proteins, lipids, carbohydrates, and water. Each of the mentioned nutrients plays a role in contributing to infant growth and development. [5,6]

  • Proteins: Proteins can help to build, strengthen and repair the tissues of the body. Also, they are needed to make antibodies, enzymes, and hormones. Breast milk has protein that is easy for babies to digest. These proteins are essential throughout every stage of the lifecycle for people to survive. Lactoferrin is a form of protein in breast milk. It moves the iron through your baby’s body. Also, it can help to protect your newborn’s intestines from infections.
  • Lipid (fats): Lipids make 4% of breast milk. They provide over half of the calories which your baby receives from it. Lipids are a great source of energy, essential fatty acids (such as DHA), and cholesterol. All of the mentioned nutrients are necessary for the development of your baby’s vision, nervous system, and brain. DHA supplements should be taken by all breastfeeding mothers.

If you are a vegan or vegetarian, then you may need a Vitamin B12 supplement. Breast milk has high – calorie content which is responsible for the baby’s healthy weight gain. Naturally, breast milk should contain all the lipids your baby needs to grow for the first six months of life.

  • Carbohydrates: This is the preferred energy source for the brain. Milk sugar, which is also known as lactose, is the main carbohydrate in breast milk. It is a known fact that human milk has more lactose than cow’s milk. Oligosaccharides are other carbohydrates found in breast milk and they promote healthy bacteria in the baby’s intestine. These bacteria can protect a baby’s gut and they can help in the fight against diseases, like infant diarrhea.
  • Water: 90% of human breast milk is made of water. Our bodies depend on water to function. Water can help to maintain hydration. It can help to regulate your body’s temperature. It can lubricate joints and can protect organs. Breast milk alone will provide all of the water required by young babies for survival.

Bioactive components:

There are some components in breast milk that cannot be found in infant formula. They are unique substances that are passed from the mother. [5,6]

  • Enzymes: There are several key enzymes that are found in breast milk. Some of them aid digestion by breaking down proteins or fats, while others give immune support. Many of the enzymes in human milk have unknown functions. Many doctors do not fully understand what enzymes do, but they play beneficial roles in infant development.
  • Hormones: Hormones have a lot of functions in the human body. Hormones influence blood pressure regulation, stress and pain responses, metabolism and growth, and development. Growth factors, thyroid hormones, and prolactin are hormones that are involved in milk production. Scientists are still learning about which hormones are transferred into breast milk (such as leptin), so they will know how they will impact the health of your baby.
  • Antibodies or immunoglobulins: These are antibodies that fight against illness and disease. They are natural immune substances, so breast milk is thought of as the baby’s first vaccine. Breast milk has properties that can help to protect against diarrhea, vomiting, ear infections, common cold, and other potentially dangerous infections. IgA (Secretory Immunoglobulin A) is the primary antibody in breast milk.

It coats the baby’s lungs and intestines, sealing them to prevent germs from entering the body and the bloodstream. Premature babies and those babies who will be attending daycare right away are especially poised to benefit from the added immune support which breast milk can provide.


Vitamins and minerals are found in breast milk and they are needed to support young babies. Also, infant formulas have many of these vital micronutrients. [5,6]

  • Vitamins: Vitamins support healthy skin, eyes, and bones. They are needed to prevent diseases of malnutrition, such as rickets and scurvy. Typically, breast milk has all the vitamins needed to support your baby’s health as he or she grows. But, if you follow some dietary restrictions, then the amount of Vitamin B6, folate, or Vitamin D may be lower. You should talk with your doctor if you need to take some vitamins to support your breastfeeding. Often, doctors recommend to women continue with taking prenatal vitamins until they finish breastfeeding.
  • Minerals: Breast milk is rich in minerals which the baby needs to grow healthy and strong. Some of the most important minerals include selenium, magnesium, chloride, sodium, calcium, zinc, and iron. Minerals are used to promote proper nerve function, produce red blood cells and build strong bones.

Breast milk is an excellent source of many important nutrients for babies. It has been shown that infant formula is a safe and healthy alternative to a mother’s breast milk. They are not exactly the same in the terms of the bioactive properties which breast milk can offer. You should talk with your pediatrician, doctor, or family member about whether breast milk is an accessible option for you and your baby.

But, you are a mother and you can only decide what is right for your child. If your baby is adequately fed, no matter if breast milk or infant formula is used, you should not be worried. Your baby is getting enough nutrients, so you will see his or her development and growth.


[1] Jama A, Gebreyesus H, Wubayehu T, et al. Exclusive breastfeeding for the first six months of life and its associated factors among children age 6-24 months in Burao district, Somaliland. International Breastfeeding Journal. 2020;15.

[2] World Health Organization. Breastfeeding. Retrieved from

[3] National Institutes of Health. Breastfeeding may help prevent type 2 diabetes after gestational diabetes. 2015. Retrieved from

[4] Gunderson EP, Hurston SR, Dewey KG, et al. The study of women, infant feeding and type 2 diabetes after GDM pregnancy and growth of their offspring (SWIFT Offspring study): prospective design, methodology and baseline characteristics. BMC Pregnancy and Childbirth. 2015;15.

[5] Ballard O, Morrow AL. Human milk composition: Nutrients and bioactive factors. Pediatric Clinics of North America. 2013;60(1):49–74. doi:10.1016/j.pcl.2012.10.002

[6] Andreas NJ, Kampmann B, Le-Doare KM. Human breast milk: A review on its composition and bioactivity. Early Human Development. 2015;91(11):629-35.


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