Immune Factors in Human Milk

 You’ve likely heard the saying that “breast is best”, and scientific research definitely backs up this claim. Breast milk is great for your baby’s belly, their skin, and even their vision. Perhaps the most important reason that breastfed babies thrive is that every little drop of breast milk is filled with miraculous components called immunological factors. These elements of human milk are biologically active bits that safeguard and promote the robust development of a healthy immune system, the system in your body responsible for fighting off illness. So, remember that every time you sit down to nurse your baby, you are providing them insane protection. In fact, even a teaspoon of breast milk contains three million germ killing cells!

What Immune Factors Will You Find in Human Milk?

There are dozens of immune factors to be found in human milk, and each one of them has a special role in things from protection against viral infection to promoting mental concentration in older babies and toddlers. However, here are a few amazingly critical immune factors you’ll be proud to pass on to your baby.

Immunoglobulin A (and IgG too!)

When your baby is born, they are already equipped with much of their necessary immune system, including macrophages, dendritic cells, and Immunoglobulin G and M. However, they are lacking in Immunoglobulin A, otherwise known as IgA. Without this immune factor, babies are at a higher risk for developing stomach and respiratory infections like the common cold, flu, and diarrhea. Human milk also contains IgG and IgM, bolstering the existing immune system even further!


Alpha2-Macroglobulin is a long way of saying lysozyme, an enzyme known for its uncanny ability to damage bacterial cell walls, breaking them open like the cracking of an egg and killing them. It’s immune factors like these that explain why, when left out at room temperature for under 8 hours, human milk has less bacteria in it than when it first was expressed!


Without this element of human milk, there will be a lack of important vitamins and minerals like B12, zinc and Vitamin A. Together, these materials help blood health and development, eyesight, memory structuring and mood, and disease prevention.


Heparin is a “soluble bacterial pattern recognition receptor,” or basically, little proteins that help our immune system recognize and track down infectious cells. These receptors are some of the oldest parts of our immune system and work with the rest of our immune factors keep your baby’s health fortified.

Human Milk’s Immune Factors Change with Your Baby

Everything about your breast milk changes from birth to toddlerhood, morning to night. From higher calories during growth spurts to more antibody production when your baby is sick, your body knows just how to make the perfect nourishing dish for your little one. Immune factors adjust positively depending on your health, your baby’s needs, and their age as well. While some immunoglobulins lower in concentration as the baby gets older, lysozymes increase with age.

Does Infant Formula Have Any Immune System Benefits?

Unfortunately, infant formula is just not able to provide immunological benefits to your baby. The only “immune factor” present is nucleotides, derived from cow proteins. These are shown to have some benefit on increasing the circumference of an infant’s head and, possibly, brain size, but that doesn’t speak to their immunological health as a whole. Mothers unable to breastfeed, however, should consider donated breastmilk.

Breast Milk is the Most Beneficial Option Available

Breast milk is free and, more importantly, the best option available for your infant. With every sip, your infant gets a mouthful of white blood cells, IgA, and a slew of other immune factors naturally created to improve your child’s health. Next time you nurse your baby to sleep, rest easy knowing you’ve given them one last dose of health before bed.

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