Ask the Experts

A: The benefits of breastfeeding are well recognized, and part of these benefits has been attributed to the presence of beneficial bacteria in the breast milk, the body’s way of ensuring the delivery of potential probiotics and inoculating the infant gut. Our knowledge of the role of gut bacteria is ever-expanding, and the last couple of years have seen important developments in defining what is now called the entero-mammary pathway.

It was once thought that these bacteria were derived from those on the mother’s skin surface. The entero-mammary pathway, however, describes a type of gut-breast axis whereby the body transports bacterial species from the gut, through the circulation to the breast, and deposits them in breast milk.

Two important studies clearly establish the existence of this pathway. Swiss researchers studied seven mother-infant pairs and their gut ecosystems. Several types of bacteria, including Bifidobacterium breve and Clostridia, that are typically associated only with the gut environment were found not only in the mother’s gut, but also in her breast milk and in her infant’s gut. This suggests that these bacteria are being directly transported between these bodily compartments.

Another study demonstrated similar results in animals. It is thought that this pathway is “chaperoned” by specialized immune cells that “select” the bacteria from the gut and direct their transportation through the bloodstream.

Given this role of bacterial organisms in breast milk, maternal dysbiosis (altered bacteria in the gut) may have some connection to mastitis (an infection of breast tissue), and one study found that supplementation with probiotics was superior to antibiotics for improving symptoms of mastitis and preventing recurrence. The next few years will undoubtedly uncover more important roles for these little bugs!8