Researchers Identify All Bacteria Strains in Breast Milk and Colostrum

by in Parenting

Breast FeedingStudies have proven, time and again, that breast really is best. Breastfed babies have more of a diversity of gut bacteria. Overall, they tend to get fewer infections, colds and illnesses. They often have fewer issues with gas and constipation. The list goes on and on. And while scientists, experts and organizations have backed the “breast is best” campaign, science has discovered very little on why breast milk is better for babies.

Antibodies from the mother have long been linked to the improved immunity of breastfed babies, but only recently have scientists uncovered the crucial healthy bacteria in a mother’s milk. But even in knowing that breast milk contains beneficial flora, no one has counted or identified the bacteria strains – at least not until recently.

Researchers from Spain recently identified all of the bacteria found in breast milk through DNA sequencing. Published in the American Journal of Clinical Nutrition, in a first of its kind study, the research shows that there is even more bacteria in breast milk than scientists could have imagined – more than 700 different types. But even more interesting is the fact that colostrum and breast milk had different types of bacteria.

“This is one of the first studies to document such diversity using the pyrosequencing technique (a large scale DNA sequencing determination technique) on colostrum samples on the one hand, and breast milk on the other, the latter being collected after one and six months of breastfeeding,” co-authors of the study, Maria Carmen Collado and Alex Mira told Medical News Today.

In colostrum, the most common strains included Streptococcus, Lactococcus, Leuconostoc, Weissella and Staphylococcus. However, in breast milk, the most common strains included Prevotella, Veillonella and Leptotrichia. But bacteria concentration wasn’t dispersed evenly among all breastfeeding mothers. Those that were considered overweight had less bacteria than those who were at a healthy weight, and mothers who delivered vaginally had a richer concentration of the bacteria than those that had a planned Caesarean birth. Because of this, researchers theorized that a mother’s hormonal state coud have an impact on the composition of her breast milk.

“The lack of signals of physiological stress, as well as hormonal signals specific to labor, could influence the microbial composition and the diversity of breast milk,” the author said, adding that they’re not even sure at this point how or why the bacteria is there. “We are not yet able to determine if these bacteria colonize the mouth of the baby or whether oral bacteria of the breast-fed baby enters the breast milk and thus changes its composition.”

While they may get to determining that later, their goal right now is to determine whether the bacteria strains serve an immune purpose or a metabolic one. Their conclusion could help the already increasing numbers of mothers who choose to breastfeed, even if it’s just sometimes.

“If the breast milk bacteria discovered in this study were important for the development of the immune system, its addition to infant formula could decrease the risk of allergies, asthma and autoimmune diseases,” the authors concluded.

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About the Author

Kate Givans is a wife and a mother of five—four sons (one with autism) and a daughter. She’s an advocate for breastfeeding, women’s rights, against domestic violence, and equality for all. When not writing—be it creating her next romance novel or here on Growing Your Baby—Kate can be found discussing humanitarian issues, animal rights, eco-awareness, food, parenting, and her favorite books and shows on Twitter or Facebook. Laundry is the bane of her existence, but armed with a cup of coffee, she sometimes she gets it done. Find out more about Kate’s books at

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