breast milkPrevious studies have proven healthy bacteria present in breast milk may be a contributing factor in the development of the infant gastrointestinal system. Proper development leads to improved nutrient absorption and proper immune system development. While doctors and researchers know breast milk is the healthiest option for infant nutrition and development, research has yet to provide a complete look at the bacterial diversity of breast milk. A recent study published in the American Journal of Clinical Nutrition reveals breast milk is much more diverse than believed.

Researchers in Spain sequenced the DNA of breast milk in hopes of identifying a complete bacterial profile. Pre and post natal breast milk was used for the study. The first type of milk analyzed was colostrum, or first milk. Colostrum is easy to digest and, according to the DNA profile, contains more than 700 strains of bacteria.

Colostrum contained high levels of Streptococcus, Leuconostoc, Lactococcus and Weissella. When breast milk from the first and sixth month was analyzed, the predominant bacteria changed to Prevotella, Veillonella and Leptotrichia. Researchers also noted that overweight women and women who gave birth via C-section did not show the same bacterial diversity as women who were of normal weight or gave birth naturally. This suggests hormones may play an important role in the bacterial diversity of breast milk.

The results of this study add another selling point for breastfeeding versus bottle feeding, but researchers also note the presence of certain bacteria in the different stages of breastfeeding could be used to formulate infant formula that more closely matches human breast milk. Study authors suggest, “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.”

Source: Cabrera-Rubio R, Collado MC, Laitinen K, Salminen S, Isolauri E, Mira A. The human milk microbiome changes over lactation and is shaped by maternal weight and mode of delivery. Am J Clin Nutr. 2012 Sep;96(3):544-51. doi: 10.3945/ajcn.112.037382. Epub 2012 Jul 25.