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What is in your breast milk? A Lactation Consultant’s Guide

As new parents you hear lots of confusing comparisons between human breast milk and formula. Most of the articles are written by parenting magazines or bloggers who “research” the pros and cons of breastfeeding vs formula feeding. The general take away is they are basically the same except breastfeeding has a few immunological components formula lacks. So basically, you are not getting a few extra options that really aren’t necessary, like leather vs cloth seats in a car. But is this true? Not really. A lot of articles written today are simply copies or paraphrases of incomplete information, giving you a very incomplete, short version of what is in your milk.

Human babies are born very immature, physically and mentally. To compensate for immature immune systems and guts, nature changed human milk into a biological weapon that can fend off almost anything until your baby’s immune system around 6 months of age starts to produce it’s own antibodies efficiently. Your baby is being exposed to organisms they have never met before once they are outside your body. They were meant to be protected by an adult immune system through breast milk. An adult immune system that responds quickly to changes in the environment, making tailor made immune responses to protect your little one from illness or make the illness mild. Children's immune systems don't fully develops until around 5 to 6 years of age.

So what is in your milk? Human milk is a rich source of protective immune factors. Proteins, oligosaccharides, cellular component, lipids milk fat globules and other human milk constituents are dumped into your milk with every feeding to protect your little one. There are over 400 compounds in human milk that combine to make different protective factors for babies, we don’t even know what they all do. This is a list of the most well-known and how they work.


Secretory IgA (SIGA) make complementary antibodies to bind with any micro-organism that comes in contact with the mother or baby to stop it from harming the infant’s mucosal membranes. SIGA helps support and develop the infant’s immune system.

Lactoferrin is a bactericide to many Gram-negative and Gram–positive bacteria, including E. coli

Lactoferrin reacts with the cell membrane of bacteria and ruptures them, preventing them from reaction with baby’s immune system

Lactoferrin also possesses antiviral qualities; it also functions as an antifungal against Candida albicans (yeast infections)

alpha– Lactalbumin kills malignant cells but not normal cells in the body.

This syndrome is called HAMLET ( Human Alpha-Lactalbumin Made Lethal to Tumor cells), this may explain the higher rates of leukemia and lymphomas in artificially fed children. HAMLET may also explain why breastfeeding reduces cancer risks in premenopausal women.

Lysozymes are an enzyme that works with SIGA and Lactoferrin to combat E. coli

Anti- Secretory Factor in human milk protects mothers against acute mastitis and infants from diarrhea

Human Milk Oligosaccharides (HMO’s)

There are about 200 different oligosaccharides in human milk.The type of human milk oligosaccharides in breast milk changes from mother to mother and varies over the duration of lactation.

Oligosaccharides functions as a prebiotic carbohydrate that are not digested by the small intestine but fermented in the colon by resident bacteria.

Fermented oligosaccharides increase the growth of bifido bacteria and lactobacilli , probiotics in the gut.

HMO’s act as false binding sites for bacteria and viruses by mimicking receptor cites on epithelial surfaces they would normally attach to.

They sweep harmful bacteria from the gut when they are eliminated from the body.

Oligosaccharides influence the composition of micro flora in the gut, building a healthier immune system.

Oligosaccharides make it difficult for pathogens to climb or attach themselves to the urinary tract of breastfed infants.

Oligosaccharides stop the absorption of a variety of pathogens that cause otitis media, respiratory infections, and diarrhea.

Human Milk Lipids and Milk Fat Globules:

Docosahexaenoic acid (DHA) is an omega-3 fatty acid that is a primary structural component of the human brain, it is so widely recognized as being important for optimum brain growth in infants that it was added to human formula.

Long-chain polyunsaturated fatty acids (LC-PUFA), such as docosahexaenoic acid and arachidonic acid; in the diet of breastfed infants increase neurodevelopmental and cognitive function along with DHA.

Free fatty acids and monoglycerides have the ability to envelope and neutralize viruses, bacteria and protozoan like Giardia, Entamoeba, E. coli and Shiga-like toxins in the infant’s colon.

Cellular components and other human milk protective factors

Neutrophils and macrophages modulate the removal of bacteria and intravascular debris.

Lymphocytes confer important immunological information to the infant, which explains the baby’s ability to accept foreign HLA donor material from the mother or a breastfed sibling with lower rejection rates.

Nucleotides responsible for lymphocyte production, maturation of GI tract and aids in HAMLET defense.

a-Defensins have an anti-HIV qualities.

Cytokines regulate many epithelial cell functions.

Hormones and growth factors promote cell growth and promote a healthy GI tract.

Anti inflammatory components facilitate defense mechanisms while minimizing tissue damage.

Soluble CD 14 works with Lactoferrin to protects baby against septic shock.

IL-7 is linked to the growth of the thymus gland, and has a role in the production of B lymphocytes.

Vitamins and minerals in breast milk have a 20% higher bioavailability than formula, insuring optimum growth and a healthy immune system in the full term infant.

So next time you hear talk about the difference between formula and breast milk. Think processed, mass produced food vs organic, healthy super food with high bioavailability that seeds the gut biome, gives optimum growth of the immune system, and brain made just for your baby by you.

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