You will probably have heard the saying ‘breast is best’, with recent campaigns promoting breast-feeding and encouraging feeding in public. The World Health Organisation indicates that from infancy through to later life, being breastfed results in reduced blood pressure and risk of obesity, type 2 diabetes, infections and disease. It is also associated with increased intelligence as an adult. What many people may not realise is that breast milk contains a large variety of bacteria. This is surprising when you consider that it is a source of antibodies for the baby, to help its immune system fight off infections. At one point, many believed breast milk to be sterile!
Let’s start with the bad, pathogenic bacteria, which cause disease. Many bacteria can be both commensal (naturally living within an organism, without harm) and a pathogen, depending on the strain of the bacteria and its surroundings. Several well-known bacteria fall into this category such as E. coli, Staphylococcus (MRSA), and Streptococcus - the bacteria that cause pneumonia. Pathogenic versions of each of these can be found in breast milk, or on the skin, which is contacted upon breastfeeding. Each of these can cause a variety of infections, including mild to severe gut infections. Salmonella can also be transmitted, and in its various forms can cause meningitis, enteritis and enterocolitis (inflammation of the gut, small intestines and the colon).
It is incredibly important to note that although a lot of breast milk will contain pathogenic bacteria, it is in very small amounts. That’s not to say that those bacteria cannot cause an infection, however; they become a far more serious issue if the milk is expressed for consumption and not stored properly, allowing the bacteria to multiply.
But despite their bad press, bacteria can actually have a positive effect. Probiotics are living microorganisms that are beneficial for your health. You will probably have heard of them as ‘friendly bacteria’ made popular through yoghurt drinks and supplements. Breast milk is a source of lots of probiotics, such as some strains of Lactobacillus, Bifidobacterium, Streptococcus and Staphylococcus. Now why are probiotics important? Not only do they aid digestion, but the presence of friendly bacteria in the gut can out-compete harmful bacteria, preventing disease. Infants take some time to develop their own established gut bacteria, and so are at risk from opportunistic pathogens, who won’t be outcompeted in that environment. One of many risks is C. diff, which can be a potentially life threatening infection of the gut. Some Lactobacilli have also been found to have an antimicrobial effect against Salmonella, another major cause of serious gut infections, which opens up a whole other aspect of antimicrobial activity.
So although breast milk can introduce both pathogenic and ‘friendly’ bacteria to infants, the combination of antibodies, inhibitory compounds and probiotic bacteria mean that in microbial terms, the benefits far outweigh the risks. It is clear that the bacteria found in breast milk are crucial in protecting and developing the infant immune system.