Breastmilk and Your Baby’s Microbiome  

Most moms agree: breastfeeding isn’t as easy as they thought it would be! But it is well worth the effort—both for you as a mom and for your baby’s lifelong health. 

For mom, breastfeeding offers a wealth of benefits including enhancing mother-infant bonding, helping speed postpartum healing, reducing stress, inducing sleep, enhancing immunity, and helping with weight loss for some women. 

For baby, breastmilk has long been touted as the “perfect food” in terms of optimal nutrient levels and digestibility. But new research has shown there’s a lot more to the composition of breastmilk than just macronutrients (proteins, fats, carbs) and micronutrients (vitamins and minerals)—It also contains a wealth of lesser-known nourishing components that build and fortify your baby’s gut microbiome while supercharging their immunity. 

Breastmilk: the original probiotic 

In addition to optimal levels of macro and micronutrients, your breastmilk is chock-full of beneficial bacteria species—also known as probiotics—which provide the building blocks for your child’s gut microbiome. Formula companies recognize this, which is why they now add probiotics to their products. However, while any addition of probiotics to infant formula is commendable and beneficial for baby, it would be impossible to match the sheer number of species (which we still don’t have an accurate count on) that exist in mother’s milk. 

Scientists believe this is why breastfed infants have less incidences of certain diseases and more robust gut microbiomes. Plus, breastfeeding plays a vital role in inoculating your baby’s digestive tract with protective bacteria after birth, which positively impacts their developing gut microbiota for years to come. This is especially important for babies who have been born via caesarean section as they do not receive the same protective microflora from the birth canal as babies born vaginally. 


Lactoferrin is present in breastmilk in the highest amounts during the first weeks after birth, and remains present for the duration of lactation. Its primary function is to assist with iron transport and absorption, which is essential for an infant’s proper growth, development, and immune function. The really amazing thing about lactoferrin is that as it binds to iron for transport, it limits the amount of iron available for bad bacteria growth giving it excellent antimicrobial properties. It’s also been found to have antifungal, antiviral, and even anticancer components. 

But there’s more… 

New evidence shows that a derivative of Lactoferrin, known as Lactoferricin, is a bacteriostatic—which means it can bind and disable components within bacterial walls and protects baby’s gut from invading pathogens. It’s even been shown effective against antibiotic-resistant bacteria, which is pretty remarkable.  

Prebiotics in breastmilk—fuel for healthy microbes 

The protective benefits of probiotics in breastmilk are remarkable. However, probiotics can only do their jobs if they have food to live on, which is where prebiotics come in. Prebiotics are a type of fiber that feeds good bacteria ONLY, allowing them to multiply and thrive within the gut and thereby reduces the risk of infections. 

The type of prebiotics found in breastmilk are called Human Milk Oligosaccharides. Like other beneficial substances, they are found in large concentrations during the first few weeks of lactation, and remain in the milk throughout breastfeeding. These fibers are not digested by your baby, but pass into the gut where they are consumed by the beneficial bacteria, enhancing their protective properties. 

These prebiotics do not feed harmful bacteria or pathogens. They are capable of adhering to bacteria and viruses and have even been shown to reduce the risk of group B strep (GBS) biofilms. 

Maternal antibodies provide additional protection  

One of the most remarkable and underappreciated things about mother’s milk is its incredible adaptability. Not only does it magically adjust nutritional composition to meet baby’s growth and development needs, but it can churn out specific maternal antibodies to protect your child as-needed. This means if you get the flu for example, your body will start making antibodies to protect your baby before you even know you’re sick (which is why the CDC recommends women continue breastfeeding during most types of illness). That’s mother nature at her best. 

Plus, all breastmilk contains a variety of “evergreen maternal antibodies” (meaning they’re present consistently throughout lactation) designed to provide passive protection while priming the infant’s immune system to defend itself at a moment’s notice. One of the earliest maternal antibodies a baby receives via colostrum is immunoglobulin A (aka: IgA), which protects against specific viruses, bacteria, and other pathogens by binding to them and preventing adherence to the intestinal wall. It’s present in larger amounts during those first few days of life, when babies are most vulnerable, and sticks around for the duration of lactation. 

Other evergreen maternal antibodies include IgM, IgD, IgE, and IgG, which can provide passive immunity against potential systemic infections like E.Coli and Streptococcus B, and intestinal inflammation. This is just a small sample of the protective antibodies in breastmilk; many others are likely still undiscovered. 

You can do this! 

The benefits of breastfeeding are gifts you can give your baby that last well beyond weaning. No, it’s not always easy. And yes, everyone’s ability and circumstances are unique. However, if you can hang in there as long as possible your baby will be stronger, healthier, and more resilient for it. 

How long should you nurse? The World Health Organization recommends exclusive breastfeeding for the first six months, then a combination of breastmilk and food, until 2 years of age. But, any amount of breastmilk is highly beneficial, so stick with it as long as you can! 

Enjoy in good health!

Dr. Alejandra Carrasco, MD, IFMCP

Family Medicine and Integrative and Holistic Medicine Doctor

A board-certified physician, Dr. Carrasco, is the bestselling author of Bloom: 7 Steps to Reclaim Your Health, Cultivate Your Desires, and Reignite Your Spark, as well as a wife and mom of three. She founded the Austin, TX functional and integrative medicine practice, Nourish Medicine, and co-founded the online resource for moms and motherhood, Hey Mami. Dr. Carrasco holds board-certifications through the American Board of Family Medicine, and the Institute of Functional Medicine. Learn more about Dr. Carrasco at 

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