Your Baby’s Microbiome Starts With the First Sip of Breast Milk

Your Baby’s Microbiome Starts With the First Sip of Breast Milk post image

Did you know that scientists have now cataloged over 500 different species of bacteria in human breast milk? Are you surprised? After all, we know that there are over 500 species of bacteria in the human gut that have been identified — and maybe much more that have not been identified. But the species in the breast milk are different than those in the gut. This indicates that we are walking super-organisms — certainly not sterile.

Breast Milk Species Change During Lactation

This study published in the Journal of Clinical Nutrition in 2012 revels changes to the breast milk microbiota. Interestingly, the breast milk species change through the course of lactation and are significantly different than in other parts of the human body.

The researchers found that the bacterial species in breast milk are also different in mothers who are obese. Additionally, the species differ due to the mode of delivery of the baby as well.

We have known that the first contact of bacteria with the neonate is from passage through the vaginal canal during birth. A child born through C-section will accumulate bacteria from the caregivers.

This study indicates that breast feeding is another very important delivery system of bacteria to the child.

Breast Milk Contains Some of the First Bacteria to Enter Human Body

According to the researchers of this study, the bacteria in breast milk are not contaminates, but rather,

the most important postpartum element in metabolic and immunologic programming of health of neonates.

These findings indicate the importance of breast feeding in fashioning the developing microbiome of the infant. We know how important beneficial bacteria are to our health and this study emphasizes the fact that there is so much we do NOT know about how they support the infant.

Samples Taken

In this study, breast milk samples were taken from colostrum, from the first month and the sixth month. The researchers noted that the human milk microbiome changed over the course of lactation.

They noted that the milk of obese mothers had less diversity and that milk samples from elective but not from nonelective mothers who underwent cesarean delivery contained a different bacterial community than did milk samples from individuals giving birth by vaginal delivery.

This suggests that it is not the c-section so much as the absence of physiological stress or hormonal signals ( in the case of elective c-section where the hours and hormonal changes associated with labor are not experienced) in the mother that could influence the microbial species in the milk.


The researchers conclude that,

Our results indicate that milk bacteria are not contaminants and suggest that the milk microbiome is influenced by several factors that significantly skew its composition. Because bacteria present in breast milk are among the very first microbes entering the human body, our data emphasize the necessity to understand the biological role that the milk microbiome could potentially play for human health.

Breast Milk is Raw

One usually doesn’t think about breast milk being raw, but it is. If breast milk isn’t contaminated then neither is the raw milk from other mammals, particularly cow.

Furthermore, the raw milk that a cow feeds it’s calf is full of the same kind of beneficial microbial communities that the calf needs to thrive. If people thought of raw milk in the same way as breast milk (and they realized that when we speak of raw milk, we are referring to milk from cows on pasture that are humanely treated) maybe there wouldn’t be so much misunderstanding about it.

If you breast feed would you then feed your child raw milk when they are old enough? Leave a comment and let me know!

This post is shared at: Small Footprint Family

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  • Jill April 12, 2013, 8:21 am

    Super interesting study! It makes me curious about a couple other things. First, if elective C-sections and non-elective C sections result in different bacteria in breast milk, I wonder about how other interventions like pitocin, epidurals, and other pain killers might effect the bacteria. Who’d a thought that the different circumstances of C-sections would have different effects on breastmilk bacteria, after all? The other thing I wonder about is the common use of hardcore antibiotic therapy for mothers who test positive for Strep B. I don’t remember even being tested for Strep B when I was pregnant with my kids 20 years ago, but now it is a routine test. A surprisingly large percentage of prego moms test positive and the normal standard of care is IV antibiotics before and during labor! I would love to see studies on the effects of THAT practice on not only the babies (and as they grow) but on breastmilk as well. The Healthy Home Economist did an article on the Strep B testing issue a while back: The increasing rate of healthy individuals being turned into drugged patients is very troubling to me, and I think the consequences largely are yet unknown.

    • Jill April 12, 2013, 9:35 am

      Hi Jill,
      Yes I think this study opens the door to many other questions about what can affect the baby’s microbiome. Your questions are good ones and i hope someone takes this further.

      I too, never had to deal with the strep issue when my son was born. It seems that every time you turn around there is a new and dangerous “procedure” that is mandated for moms and kids…

    • Christina July 21, 2015, 7:25 am

      Jill – I had exactly the same two thoughts! I would love to find answers. Thank you for wording it so well! 🙂

  • Olivia April 12, 2013, 9:33 am

    My daughter is 16 months old and although she has had cow’s milk, I’m waiting until my raw milk share starts to really give her cow’s milk on a regular basis. I also give her raw milk cheese and grassfed butter right now. From what I have read raw cow’s milk contains the enzymes to aid in our digestion of it, and these enzymes are killed when it is pasteurized.

    I remember when Lucy was born I was very nervous about her breastfeeding because we had an emergency c section. She had absolutely no problems latching on and breastfeeding was never an issue for us. A few weeks later it occurred to me that due to my 41 hours of labor before I the c section, we both had all of the wonderful hormones that come from a natural childbirth. The only thing is that about 6 months after the birth a naturopath suggested that both Lucy and I get on a probiotic to help with the fact that she did not have a vaginal birth and that I was given antibiotics after the surgery.

  • Kate April 12, 2013, 12:53 pm

    I would absolutely feed my baby raw cow’s milk. I put way more faith in the thousands of years in history than what the more modern technological changes have done to our food supply. It is scary how we have made all these changes and assume they are great when our population is declining in overall health.

  • Heather@Mommypotamus April 15, 2013, 8:30 am

    Wow, that is fascinating about the difference that elective/non-elective caesarians make in the bacterial composition of breast milk! Thank you for this post, Jill!

  • Emily April 15, 2013, 3:35 pm

    Absolutely! We’ve given our daughter raw cow’s milk, yogurt, and cheeses with no issues. I have more confidence in a dairy farmer who I have talked to and can contact personally rather than nonentities that combine milk from a huge range of cows of dubious health.

  • Brenda April 18, 2013, 9:18 pm

    “If breast milk isn’t contaminated then neither is the raw milk from other mammals, particularly cow.”

    Well, this is a logical fallacy because it assumes that the production of the product is the same when it is not. For one thing, a humans mammary glands are not located next to their anus. Secondly, there is the human error factor in the handling and processing of raw milk. I grew up drinking raw milk, that being said, I would not feed my child raw milk because I don’t live close enough to a farmer who provides it, and I would want to be able to visit the farm weekly. Who produces your milk matters. One of the producers a little over an hour from me had an e.coli outbreak last year. They are good people with a good farm, whom I had bought vegetables and such from before, but good people also make mistakes, so I would also look for a farm that makes their monthly test results available. If I could have a cow, then I would give raw milk without a doubt.

    • katie May 30, 2013, 6:25 pm

      Brenda – I share your feelings on raw milk. The statement: “If breast milk isn’t contaminated then neither is the raw milk from other mammals, particularly cow.” seems to overlook the big differences in personal hygiene between humans and cows 😉

  • Maggie September 11, 2013, 3:33 pm

    I know this is an older post but I wanted to comment in case others are looking to research how to replenish your newborn’s gut bacteria after a c-section (with required antibiotics). Because of earlier surgery to my uterus, I have to have a scheduled c-section (don’t say “elective”!) this winter and I am coming up with a plan of action for my baby after it’s born. I think this will include probiotics for me and him/her, lots of fermented food for me, breast milk for the baby and I am going to inoculate her/him orally with vaginal secretions several times after birth to simulate the bacteria from a vaginal birth. (They get quite a mouthful of vaginal material during a typical vaginal birth, apparently.)

    • Jill September 11, 2013, 10:11 pm

      Hi Maggie,
      Sounds like a plan!

  • nicole August 3, 2014, 7:20 pm

    Great article! I wonder about the effects on colostrum of using antibiotics during delivery on gbs positive moms. We already know it effects the vaginal flora passed to baby but of course the potential risk of meningitis in a neonate is not with messing around.

    Yes to raw milk!!!!!