The Composition of Breast Milk

Explore the Nutritional Benefits and Components of Breast Milk

For human babies, human breast milk is the ideal source of food and nutrition. Due to the chemical makeup of breast milk, health organizations around the world recognize the importance of it for young children.

Breastfeeding is recommended exclusively for the first six months of life. After that period, breastfeeding is still recommended, along with the addition of solid foods, for a year, two years, or even longer. So, what's in breast milk that makes it the best choice?

Breast Milk Is Personalized

A mother produces breast milk specifically for her child. It contains everything that a human baby's body needs to grow, develop, mature, and survive. It's not only a complete source of nutrition, but it also helps to protect children from disease and illness as they grow.

Breast Milk vs Infant Formula

As scientists study breast milk, they have discovered so far that it contains over 200 different ingredients so far. We don't even know the full composition of breast milk or the importance and function of many of the contents yet.

Without a complete analysis and a real understanding of what each element in breast milk does, it makes it very hard for the manufacturers of infant formula to try to copy its composition. Even though infant formula is a safe, acceptable alternative to breast milk, it's not equal. It's just not possible to recreate the makeup and ever-changing status of breast milk.

The Composition of Breast Milk

Of the many components that we currently know about in breast milk, a few stand out. We're familiar with water, carbohydrates, lipids, and proteins, but let's explore how these factor into the nutritional value of your breast milk and how they help your baby grow and develop.



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

Breast milk is made up of about 90 percent water, and the rest of its contents can be found in that water. The human body needs water for almost everything it does. Among other things, it keeps your baby hydrated, helps to 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.

Compared to cow's milk, there is much more lactose in human milk. Lactose not only provides your baby with a major source of energy for growth and development, but it's also linked to greater brain development.

Other carbohydrates found in breast milk such as oligosaccharides are needed to promote healthy bacteria in the intestines. These bacteria protect your baby's gut and help fight off infant diarrhea.


Lipids (Fats)

Lipids may only make up about 4 percent of breast milk, but they provide 50 percent of the calories that your baby gets from your milk.

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

Lipids are also responsible for your baby's weight gain as he grows. Your breast milk should contain all the lipids that your little one needs. However, if you're on a vegetarian diet, discuss whether or not you should take a DHA supplement with your doctor to be sure you're getting enough.



Proteins build, strengthen, and repair the body. They are also needed to make hormones, enzymes, and antibodies. The protein in your breast milk is very easy for your baby to digest and your child needs protein to grow and develop.

One very important protein in breast milk is lactoferrin. Lactoferrin moves iron through your baby's body, but it also helps to protect your newborn's intestines from infections.  


Immunoglobulins (Antibodies)

Immunoglobulins are antibodies that fight off the germs that 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 found in breast milk can also help protect your child from the common cold, ear infections, vomiting, diarrhea, and other dangerous infections that affect newborns and infants.​

The main antibody in your breast milk is Secretory Immunoglobulin A (IgA). IgA coats your baby's lungs and intestines. It seals them to prevent germs from entering your baby's body and blood. The antibodies in your breast milk are even more important if you have a premature baby or a baby who will go to daycare. 



Hormones have many jobs in the human body. They control growth and development, metabolism, stress, pain, and blood pressure.

The hormones in breast milk are prolactin, thyroid hormones, growth factors, relaxin, endorphins, erythropoietin, cortisol, leptin, estrogen, progesterone, and more. Scientists are still studying the hormones in breast milk, trying to learn more about them and what they do for your baby. 



There are important enzymes in human breast milk. Some enzymes help with digestion by breaking down fats or proteins, and others protect your baby from germs and illness. There are also enzymes which scientists aren't sure what they do.

While we don't know the functions of all enzymes, we do know that they play an important role in the health and development of your child.  



Vitamins contribute to healthy bones, eyes, and skin. They also help to prevent diseases such as scurvy and rickets. Your breast milk contains the vitamins that are necessary for your baby's health as she grows.

However, the amount of Vitamin D, folate, or, depending on your diet, Vitamin B6 may be lower in certain women. Therefore, talk to your doctor and your baby's doctor about the recommended vitamin supplements that you may need to take while you're breastfeeding.



Breast milk is full of minerals. Some of the minerals in your breast milk are iron, zinc, calcium, sodium, chloride, magnesium, and selenium.

Minerals, like vitamins, are needed for healthy growth and development. They help to build strong bones, make red blood cells to transport oxygen through the body, and keep muscles and nerves functioning properly.

A Word From Verywell

Breast milk is a nutritious food source for your baby, so it is worth considering breastfeeding over formula. Be sure to talk to your doctor about whether it's right for you and your baby. You can ask about any dietary changes or supplements that may help as well.

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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.