The Composition of Breast Milk

Explore the Nutritional Benefits and Components of Breast Milk

For human babies, the chemical makeup of human breast milk makes it an ideal source of food and nutrition. Health organizations around the world recognize breast milk as a highly nutritious option for infants and young children.

Breastfeeding is recommended exclusively for the first six months of life. The recommendation to breastfeed continues, along with the addition of solid foods, for a year, two years, or longer.

What's in breast milk that makes it such a highly recommended choice?

Breast Milk Is Personalized

Breast milk is produced by a woman's body specifically to feed a child. It contains everything that a human baby's body needs to grow, develop, mature, and survive.

Not only is breast milk a complete source of nutrition but it also helps protect babies and young children from disease and illness.

Breast Milk vs. Infant Formula

Breast milk is composed of hundreds of distinct bioactive molecules. We don't yet know the full composition of breast milk nor the importance and function of its contents.

Without a complete analysis and a real understanding of what each element in breast milk does, it makes it hard (if not impossible) for manufacturers of infant formula to copy its composition.

While infant formula is a safe, acceptable, alternative to breast milk, it is not equal. It's simply not yet possible to recreate the makeup and ever-changing status of breast milk in a formula.

The Composition of Breast Milk

Of the many components we know exist in breast milk, a few stand out because they are familiar to us. We know the importance of water, carbohydrates, lipids, and proteins in the human body, but let's explore how these elements affect the nutritional value of human breast milk to help an infant grow and develop.



Mother breastfeeding baby girl (3-6 months) in bed

Human breast milk is made up of about 90 percent water. The remainder of its contents can be found in the water. The human body needs water for almost everything it does. Among other tasks, water maintains hydration, helps regulate body temperature, lubricates joints, and protects organs. 



Carbohydrates are the body's number one source of energy. The main carbohydrate in your breast milk is the milk sugar known as lactose.

Human milk has more lactose than cow's milk. Not only does lactose serve as a major energy source for your baby's growth and development, but it's also been linked to brain development.

Other carbohydrates found in breast milk (such as oligosaccharides) promote healthy bacteria in your baby's intestines. These bacteria protect your baby's gut and can help fight off diseases like infant diarrhea.


Lipids (Fats)

Lipids may only make up about 4% of breast milk, but they provide over half of the calories that your baby gets from breastfeeding.

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

All breastfeeding mothers should take a DHA supplement. If you are vegetarian or vegan, you may also need a B12 supplement.

These lipids are also responsible for your baby's weight gain. Your breast milk should contain all the lipids your baby needs as they grow.



Proteins build, strengthen, and repair the body's tissue. They are also needed to make hormones, enzymes, and antibodies. The protein in your breast milk is easy for your baby to digest. Children continue to need protein to support growth and development as they get older.

One essential protein in breast milk is lactoferrin, which moves iron through your baby's body. It also helps protect your newborn's intestines from infections.  


Immunoglobulins (Antibodies)

Immunoglobulins are antibodies that fight off germs that can cause illness and disease. Your breast milk is like your baby's first vaccine. It contains antibodies that fight off bacteria, viruses, fungus, and parasites.

The immune properties of breast milk can also help protect your baby from the common cold, ear infections, illnesses that cause vomiting and diarrhea, and other infections that can be potentially dangerous for infants.​

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

Antibodies in your breast milk are even more important if you have a premature infant or are planning to send your child to daycare.



Hormones have many jobs in the human body. They are involved in growth and development, as well as the function of the body's metabolism, response to stress and pain, and blood pressure regulation.

The hormones involved in milk production include prolactin, thyroid hormones, growth factors.

Scientists are still researching the hormones that are actually found in breast milk (such as leptin) to learn more about how they might affect a baby's health.



There are several key enzymes found in human breast milk. Some of these enzymes aid digestion by breaking down fats or proteins, while others protect your baby from germs and illness.

The functions of several enzymes found in human breast milk are unknown. While we might not know what all these enzymes do, it's likely they play an important role in a baby's health and development.



Vitamins support healthy bones, eyes, and skin. They are also necessary to prevent diseases such as scurvy and rickets.

Breast milk typically contains all the vitamins needed to support your baby's health as they grow. However, the amount of vitamin D, folate, or vitamin B6 in your body may be lower if you follow a certain kind of diet.

Talk to your doctor and pediatrician if there are any vitamin supplements you should take while you are breastfeeding.



Like vitamins, breast milk is also full of minerals your baby's body needs to grow healthy and strong, including iron, zinc, calcium, sodium, chloride, magnesium, and selenium.

Minerals are needed to build strong bones, make red blood cells to transport oxygen throughout their body, and promote healthy muscle and nerve function.

A Word From Verywell

Breast milk is a nutritious food source for your baby. While infant formulas are a safe and healthy alternative to breast milk, they are not exactly the same in terms of the nutrition they offer.

Talk to your doctor and pediatrician about whether breastfeeding is the right choice for you and your baby.

While human breast milk generally provides complete nutrition, your doctor might recommend that you make changes to your diet or take supplements to ensure that your breast milk contains enough of the vitamins and minerals your baby's growing body needs.

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Article Sources
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  1. Boquien CY. Human milk: An ideal food for nutrition of preterm newbornFront Pediatr. 2018;6:295. doi:10.3389/fped.2018.00295

  2. World Health Organization. Exclusive breastfeeding for six months best for babies everywhere. Updated January 2011.

  3. Ballard O, Morrow AL. Human milk composition: nutrients and bioactive factorsPediatr Clin North Am. 2013;60(1):49–74. doi:10.1016/j.pcl.2012.10.002

  4. Martin CR, Ling PR, Blackburn GL. Review of infant feeding: Key features of breast milk and infant formulaNutrients. 2016;8(5):279. doi:10.3390/nu8050279

  5. Popkin BM, D'Anci KE, Rosenberg IH. Water, hydration, and healthNutr Rev. 2010;68(8):439–458. doi:10.1111/j.1753-4887.2010.00304.x

  6. Romero-Velarde E, Delgado-Franco D, García-Gutiérrez M, et al. The importance of lactose in the human diet: Outcomes of a Mexican Consensus MeetingNutrients. 2019;11(11):2737. doi:10.3390/nu11112737

  7. Doherty AM, Lodge CJ, Dharmage SC, Dai X, Bode L, Lowe AJ. Human milk oligosaccharides and associations with immune-mediated disease and infection in childhood: A systematic reviewFront Pediatr. 2018;6:91. doi:10.3389/fped.2018.00091

  8. Mazzocchi A, D'Oria V, De Cosmi V, et al. The role of lipids in human milk and infant formulaeNutrients. 2018;10(5):567. doi:10.3390/nu10050567

  9. Yang Z, Jiang R, Chen Q, et al. Concentration of lactoferrin in human milk and its variation during lactation in different Chinese populationsNutrients. 2018;10(9):1235. doi:10.3390/nu10091235

  10. Gregory KE, Walker WA. Immunologic factors in human milk and disease prevention in the preterm infantCurr Pediatr Rep. 2013;1(4):10.1007/s40124-013-0028-2. doi:10.1007/s40124-013-0028-2

  11. Palmeira P, Caneiro-Sampaio M. Immuniology of breast milk. Rev Assoc Med Bras. 2016;62(6). doi:10.1590/1806-9282.62.06.584 

  12. Savino F, Liguori SA, Fissore MF, Oggero R. Breast milk hormones and their protective effect on obesityInt J Pediatr Endocrinol. 2009;2009:327505. doi:10.1155/2009/327505

  13. Dallas DC, German JB. Enzymes in human milkNestle Nutr Inst Workshop Ser. 2017;88:129–136. doi:10.1159/000455250

  14. Dror DK, Allen LH. Overview of nutrients in human milkAdv Nutr. 2018;9(suppl_1):278S–294S. doi:10.1093/advances/nmy022

Additional Reading
  • Lawrence RA, Lawrence RM. Breastfeeding: A Guide For The Medical Profession. 8th ed. Philadelphia, PA: Elsevier Health Sciences; 2015.

  • Riordan J, and Wambach K. Breastfeeding and Human Lactation. 5th ed. Sudbury, MA: Jones and Bartlett Learning; 2015.

  • American Academy of Pediatrics. New Mother’s Guide To Breastfeeding. New York, NY: Bantam Books; 2011.