Learning Center > What’s in Breast Milk and How Does It Support Your Baby’s Development?

What’s in Breast Milk and How Does It Support Your Baby’s Development?

baby sleeping,eye close-up

By: Dr. Erin Qualter


Breast milk is designed by nature to supply all the essential nutrients needed for a baby to grow and thrive. If we trust evolution and mother nature, we should trust that all the ingredients in breast milk are there for a reason and serve an important purpose.

Here are all those important ingredients (macronutrients and micronutrients), the amount contained in breast milk, and how they work to provide baby with well-balanced nutrition.

The primary ingredient: water (88%)
Breast milk is primarily water which keeps infants hydrated, but it’s also packed with a variety of macronutrients that give babies everything needed to thrive, including:

Fuel for the developing microbiome: carbohydrates (7%)
Carbohydrates are the predominant macronutrient in breast milk and handle the early establishment of an infant’s microbiome.

Lactose: The primary carbohydrate in breast milk is lactose. This is readily digested by almost all infants due to the presence of an enzyme called lactase which is found on the surface of the small intestine.

Human milk oligosaccharides (HMOs): HMOs are the second most abundant carbohydrate after lactose and the third most abundant solid component. There are over 200 types of HMOs contained in human breast milk. HMOs are exclusively produced in lactating mammary glands and have not been found in infant formulas up until very recently.

Unlike lactose, infants are not able to digest HMOs on their own. Without a bacteria called Bifidobacterium infantis, the HMOs cannot be digested and exit unutilized in stool. B. infantis has the enzymes needed to break down HMOs into key signaling molecules that help to develop and direct the infant’s immune system.

Unfortunately, countries like the United States where modern interventions such as antibiotics, C-sections, and formula are high, show a near extinction of B. infantis in babies born today. Fortunately, feeding Evivo®, which contains B. infantis EVC001 can reintroduce this beneficial bacteria strain back into the infant’s lower gastrointestinal tract where it colonizes (thrives and persists) and digests these very important HMOs. Once colonization takes place, the pH in an infant’s gastrointestinal tract will become more balanced.

Supporting growth and development: protein (1%)
The protein in human breast milk is mainly a mixture of whey and casein, which is necessary for growth and development. Whey is a liquid that is easily digested. Casein is solid and present in clots or curd in the stomach which are not easily dissolved. The whey-to-casein ratio varies according to the time in which breast milk is produced. The ratio is considered high at approximately 90:10 in colostrum, but this ratio changes over time in mature milk to 60:40.

Other micronutrients in breast milk (< 1%)
Micronutrients contained in breast milk include iron, calcium, phosphorus, magnesium, sodium, chloride, potassium, manganese, iodine, selenium, copper, and zinc. Growth factors and hormones are also contained in breast milk. Breast milk even has its very own microbiome with many bacteria such as Staphylococcus, Streptococcus, Lactobacillus, and Propionibacterium. Lastly, breast milk contains abundant microRNA which plays a role in developmental programming.

As you can see, breast milk has an amazing array of nutrients that have a significant impact on infant development. When you add Evivo into the equation, babies fully maximize nutrition from breast milk. That’s because Evivo is clinically shown to allow infants to use the full spectrum of nutrients in breast milk more effectively and efficiently.1 In combination with breast milk, Evivo helps support the development of the infant gut microbiome to build a foundation for better health.

About the Author
Erin Qualter, M.D., Neonatologist
Dr. Qualter is a Clinical Implementation Director at Infinant Health, and a neonatologist who cares for babies at Monmouth Medical Center in Long Branch, New Jersey. Her passion lies in caring for infants, optimizing their care and outcomes through the best nutrition options. That’s why she is committed to educating providers about Evivo’s ability to restore what nature intended for babies. She received a Master’s in nursing from Columbia University, where she was a Clinical Research Nurse Practitioner at the Children’s Hospital of New York-Presbyterian at Columbia University Medical Center. Outside of work, she is the proud mother of three who enjoys spending time with her kids.


  1. Duar RM, et al. “Comparative Genome Analysis of Bifidobacterium longum subsp. infantis Strains Reveals Variation in Human Milk Oligosaccharide Utilization Genes among Commercial Probiotics.” Nutrients. 2020 Oct 23;12(11):3247.