What’s In Breast Milk?

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Estimated reading time: 7 minutes

Besides an occasional hot dog or Starburst, I like to know what ingredients are in the food I eat. (With that hot dog or Starburst, however, it’s just better to not even ask.) All kidding aside, society seems to now care even more about the impacts of the ingredients we eat. In particular, more parents now read the food label before handing their kid a snack. So you might be wondering, “What’s in breast milk? What is my baby actually eating?!” Well, good news, you can’t get more organic than mama’s milk. Let’s talk all about the goodness in breast milk! 

What’s In Breast Milk: The Ingredients

Scientists still continually find new components and benefits of breast milk (3; 6). Breast milk includes the following ingredients.


One of the most important and unique components of breast milk is antibodies (1; 2; 3; 5). Antibodies protect your baby from illnesses and infections. Specifically, they can neutralize bacteria and viruses. Altogether, there are five types of antibodies, and breast milk contains all five!

Growth Factors and Hormones

Breast milk also contains growth factors (1; 3; 7). These support healthy growth in the following areas:

  • Intestines
  • Blood vessels
  • Immune system
  • Nervous System
  • Brain
  • Glands & Hormones

Additionally, breast milk contains all of the following hormones: prolactin, oxytocin, prostaglandins, insulin, thyroid stimulating hormone, adrenal steroids, relaxin, thryoxine, and epidermal growth factor. Hormones have the following benefits (1; 3; 5; 7):

  • Regulate appetite
  • Help sleep patterns
  • Produce a strong sense of love, attachment, and peace
  • Help mom and baby bond

Minerals and Vitamins

Breast milk contains all the following minerals: sodium, zinc, iron, calcium, copper, magnesium, selenium, and other trace elements (3).

Vitamin D and K are present in breast milk, though in small traces. (Click here to learn more about why breastfed babies need Vitamin D.) Minerals and vitamins have the following benefits (1; 3):

  • Help your baby grow
  • Support organ function
  • Build your baby’s teeth and bones
  • Help eyesight (Vitamin A)
  • Provide antioxidant (Vitamin E)

More Goodness!

Breast milk also has the following components:

  • Live Cells (3)
    • White Blood Cells
      • Fight infection and boost immunity
    • Stem Cells
      • May support organ development and repair
  • Proteins (1; 3)
    • Help your baby grow and develop 
    • Activate immune system 
    • Develop and protect neurons in your baby’s brain 
  • Amino Acids & Nucleotides (1; 3)
    • May help induce sleep and develop healthy sleep patterns
  • Oligosacchrides (Complex Sugars) (3)
    • Act as prebiotics (‘good bacteria’ that protect your baby’s gut)
    • Protect bloodstream from infection 
    • Lower risk of brain inflammation
  • Enzymes (3)
    • Help speed up chemical reactions in your baby’s body
    • Absorb iron
    • Help digestion
    • Support immune system
  • Fatty Acids (1; 3)
    • Help develop the following areas:
      • Nervous System
      • Brain
      • Eyes
      • Vascular Tissue
  • MicroRNAs (3)
    • May regulate gene expression
    • Prevent diseases
  • Carbohydrates (Lactose) (1)
    • Absorb calcium and iron
    • Provide energy to your baby’s brain
    • Help digestion

What’s in Breast Milk: It Adapts!

Did you know your milk is unique to you and your baby? And do you know what’s really crazy? Breast milk is a living fluid (3). It adapts to what your baby needs at any given moment (1; 3). Really! It’s true! This aspect alone makes breast milk superior to formula. Your custom-made milk recipe will change in the following ways to help your baby:

Your Baby’s First Week 

Breast milk drastically changes during the first few weeks of your baby’s life (4). In your baby’s first few days, the milk you produce at first is called colostrum. Colostrum has the following properties (4):

  • Thick
  • Low volume
  • High protein
  • Easy to digest

During the first week of your baby’s life, colostrum transitions to mature milk (2). Mature milk is designed for your rapidly growing baby. It has the following properties (5):

  • Higher volume
  • Lower protein
  • Higher in lactose and fat

Premature Babies

If your baby is born preterm, your colostrum and mature milk will produce more protein, different types of fats, and antibodies that a preterm baby specifically needs (2; 5).  

Breast Milk at Each Feeding

Breast milk changes fat content depending on how long it’s been since the last feeding (5; 6). Also, it changes if it’s hot or cold outside, by adjusting the water or fat content (6).

Breast milk even changes during each feeding! As the feeding begins, your milk starts out low in fat and gradually increases. Hindmilk, or the fattier milk produced a few minutes into each feeding, provides more calories, fat, and protein. So this helps your baby end each feeding feeling full and satisfied (6; 7). 

Breast Milk When You’re Sick

As mentioned before, breast milk contains antibodies that help prevent sickness (2). For example, if you develop a cold while breastfeeding, your body produces antibodies to help you fight that cold. These special antibodies will also pass to your baby through your breast milk. This new and improved breast milk recipe will help your baby heal quickly from the cold or help him avoid getting the cold altogether (5).

As Your Baby Grows

Breastfeeding works as a supply and demand system. The more your baby eats, the more milk you produce. This allows your baby to tell you how much milk she needs. Additionally, she can receive just the right amount of nutrients she needs at any stage of growth (5). 

What’s In Breast Milk vs. Formula

Breast milk is impossible to duplicate (3; 5). As scientists continue to find new components of breast milk, formula manufacturers cannot keep up (6)! Breast milk contains at least over 200 nutrients not found in formula (7)! Breastfeeding is certainly the ideal recipe to feed your baby.

Formula is typically made from processed cow’s milk (4), though there are different types of formula, including goat’s milk or soy. Ingredients vary by type, brand, or country, but formula might contain the following (4):

  • Emulsifiers and stabilisers (help the oils and water mix when you make it)
  • Lactose (a natural sugar found in milk) and/or other sugars (such as corn syrup, fructose or maltodextrin)
  • Plant-based oils (such as palm, rapeseed, coconut, sunflower and soybean oil)
  • Fatty acids (usually derived from fish oil)
  • Vitamins and minerals (from plant and animal sources)
  • A couple of enzymes and amino acids
  • Probiotics (in some formulas)

Compared to formula, breast milk is better across the board. A few more benefits of breast milk to note (3; 6): 

  • Easier to digest
  • Less sodium and protein (better for your baby’s kidneys)
  • Baby can better absorb calcium and other nutrients

Click here to learn more about the countless benefits of breastfeeding.

Special Situations

Although breast milk is ideal, special situations may prevent you from breastfeeding (5). In those cases, there are options! For example, babies can receive expressed milk, milk from a food bank, or formula. If you have any questions or doubts, talk to your caregiver. You can also consult a lactation consultant, your baby’s caregiver, or a childbirth educator (7). 

How you feed your baby does not reflect on who you are as a loving parent. Every situation is different. No matter how you feed your baby, you should feel supported. After all, you’re keeping a little human alive, nourished, and loved. You’re amazing!

Kopa Birth’s online childbirth classes allow you to prepare for a natural childbirth in the comfort of your own home, 24/7. Enroll today in our free online childbirth class to learn more about preparing for natural childbirth. 


  1. CAPPA: Childbirth & Postpartum Professional Association. (2016). Lactation Educator Manual (Ninth Edition).
  2. Injoy Health Education. 2016. Understanding Breastfeeding: Your Guide to a Healthy Start (Seventh Edition). Longmont, CO: InJoy Birth & Parenting Education.
  3. Medela AG. 2019. Breast Milk Composition. Retrieved December 11, 2020, from https://www.medela.com/breastfeeding/mums-journey/breast-milk-composition
  4. Medela AG. 2019. Breast Milk vs Formula: How Similar Are They?. Retrieved December 11, 2020, from https://www.medela.com/breastfeeding/mums-journey/breast-milk-vs-formula
  5. Meek, J.Y., Yu, W., American Academy of Pediatrics. (2011). New Mother’s Guide to Breastfeeding (Second Edition). New York, NY: Bantam Books Trade Paperback
  6. Rosenthal, M.S. (2000). The Breastfeeding Sourcebook (Third Edition). Lincolnwood, IL: Lowell House.
  7. Simkin, P., Whalley, J., Keppler, A., Durham, J., & Bolding, A. (2016). Pregnancy, Childbirth, and the Newborn: The Complete Guide (Fifth Edition). Minnetonka, MN: Meadowbrook Press.

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Meet Katie Griffin

I’m a registered nurse, Lamaze certified childbirth educator, and the mother of 7. I help women realize their dream of a natural, intimate, and empowering hospital birth.

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Besides an occasional hot dog or Starburst, I like to know what ingredients are in the food I eat. (With that hot dog or Starburst, however, it’s just better to