The Microbiome and The Science of Human Milk

Breastfeeding is as fascinating as it is wonderful and as it is challenging. I loved learning more about the science behind breastfeeding, and breast milk, with Microbiome Courses, which reiterated to me just how important it is to support mothers to breastfeed, if they choose to.

Breastfeeding is healthy (for mum and baby), natural and practical. Mothers who breastfeed have a lower chance of developing breast cancer, ovarian cancer, heart disease or stoke, type 2 diabetes or postnatal depression, women aged 50 who had breastfed performed better in cognitive tests and the longer you feed for the more protection you receive. It promotes bonding, decreases risk of SIDS, allergies, reduces chance of ear infections, respiratory infections and gastroenteritis, febrile convulsion, pneumonia, acute bronciolitis, asthma (asthma is linked to higher risk for 36 other ‘diseases’ – e.g. sleep disorders or depression), obesity and short stature, adhd, asd and hypertrophic pyloric stenosis, breastfed children score higher in neucognitive tests and breastfeeding at the breast (vs. expressed milk) has been shown to affect working memory/ executive function up to age 6.

Breastfeeding is also physically and emotionally difficult, it’s not the only way and it’s not for everyone which is why my favourite phrase when it comes to infant feeding is “breast is not best, fed is not best, informed and supported is best”. 81% of UK mothers initiate breastfeeding but only 1% are still feeding by 6 months (Unicef data in 2022). 63% of mothers would have liked to breastfeed for longer and there are many reasons that parents stop breastfeeding including early introduction of formula before discharge from hospital, separation of mother and baby, lack of support (especially by the medical community), wanting partners to be involved in baby care, a bottle feeding culture where formula is the norm and lack of education on the first 48 hours of life.

You are more likely to establish and continue breastfeeding if you hire a doula, so get in touch if you’d like to chat about how I could support you.

So, the science bit…it took me a while to make sense of all of this and even longer to write it into a reasonably easy to understand format!!

1)   During vaginal birth, the mother transfers her unique bacterial ecosystem to her baby. The bacteria coming from Mum colonise the infant gut and crowd out the pathogens; they are the bacteria to optimally train the infant immune system, giving protection for life

2)   These microbes are then fed by the unique sugars - the human milk oligosaccharides (HMO’s) - in Mum’s breast milk, which are matched to the bacteria that were passed to the baby during vaginal birth. These HMO’s are the 3rd most abundant component of milk, but are indigestible by the baby, they are there specifically to feed the infant gut microbiome

Caesarean birth, antibiotics and formula feeding, whilst sometimes necessary but widely overused, alter this process and if the microbiome doesn’t develop normally in early life you can have a misfiring of the immune system which can increase risk of asthma, allergies, diabetes and obesity etc.

Human breast milk is species-specific; this means it is exquisitely designed for the feeding of human infants – just as cows milk (the base for most formulas) is designed for baby cows. It is also specifically designed for the baby’s unique needs and age. It is a functional food containing macro nutrients (proteins, carbohydrates, fats and lipids - everything a baby needs to grow), oligosaccharides, growth factors, hormones, signalling agents, cytokines that influence the immune system and help protect the baby from infection, plus micronutrients (vitamins and minerals) - many of our essential nutrients are difficult to absorb so the nutrients in breast milk are complex to make sure that every single one is absorbed.

Breast milk is a personalised medicine. It is a live tissue containing bioactive components (microbes), antibodies and live white blood cells to fight bacteria and viral infection - this increases when Mum is unwell, immune cells, epithelial cells and stem cells which can cross the gut and migrate into the blood of the baby and into their brain helping with cognitive function maturation, and develop the blood system, the lymph system and the skeletal system. The mum and the baby are sharing the same environment, so if there are exposures or pathogens in the environment, mum will sense those and her milk will adapt.

Lactose (7% of human milk) and human milk oligosaccharides (HMOs) (1-2% of human milk) are both sugars found in human milk. Lactose is digested by the baby and provides energy; the infant does not digest HMO’s, they are intact in the large intestine and colon and then serve as prebiotics for specific supportive bacteria – they are food for the beneficial microbes in baby’s gut.

Babies are born reasonably sterile and their guts need to be colonised by microbes. Part of the reason the immune system is not developed in a foetus is to prevent the mother’s body from rejecting it - this is often the cause of recurrent miscarriage, which was believed to be the cause of my own recurrent miscarriages – but this means babies are born on a path for inflammatory, allergic and autoimmune disease if the microbiome is not corrected.

Breast milk farms that microbiota, controlling which microbes end up in the infant gut - protecting the infant from disease and contributing to general health by changing responses of epithelial cells, immune cells and the infant system to certain diseases and priming the infant for preventing diseases later on in life. Many immune-related diseases that we see today are largely related to the microbiome so the single most important thing we can do for a healthy baby across a life-course is to ensure the microbial seeding occurs completely at birth through vaginal delivery, vaginal seeding if baby needs to be born via C-section, immediate and uninterrupted skin-to-skin contact and that the microbes are then supported through breastfeeding for a significant duration.

Feeding at the breast is better than bottle-feeding expressed milk. This is partly because breast milk is tailored to the time of day; circadian rhythms start developing in utero and eternal time cues in mothers’ milk helps babies develop their body clock. If feeding expressed milk, the dynamic relationship changes slightly as the feedback loop is disrupted - if the baby is sick mum’s milk composition changes when feeding at the breast  - we think through their saliva - so if the baby is being fed expressed milk this change does not happen. If using expressed milk then fresh is better than frozen as it will be a closer match to the babies specific age and needs, also, freezing breast milk has also been shown to alter the bacteria in the milk, with long term freezing having a greater effect than short term freezing.

These principles can also be applied to when donor milk is being used, especially as donor milk is typically from mums with older babies so it is not the best composition for younger babies. In addition, donor milk is pasteurised which kills the healthy bacteria as well as pathogens, but it does still contains many things that formula doesn’t so is a good option where direct breastfeeding from the mother is not an option.

Below is the list of lactation scientists that contributed to this course from the Microbirth School, I hope I have managed to unpick the information to explain the science, a bit! Research on the microbiome and the science of human milk is ongoing, there is so much more to learn.

·      MEGHAN AZAD, Assistant Professor at the University of Manitoba, Department of Paediatrics and Child Health. Research Scientist at the Children's Hospital Research Institute of Manitoba. Canada Research Chair in Development Origins of Chronic Disease and co-Director of the Manitoba Interdisciplinary Lactation Centre.

·      GREGOR REID, Professor of Microbiology and Immunology and Surgery at Western University, and the Endowed Chair in Human Microbiome and Probiotics at the Lawson Health Research Institute.

·      RODNEY DIETERT, Emeritus Professor of Immunotoxicology, Cornell University

·      BRUCE GERMAN, Professor and Food Chemist, Food Science and Technology Director, Foods for Health Institute, University of California Davis

·      DAVID MILLS, Professor and Peter J Shield’s Endowed Chair in Dairy Food Science, Food Science and Technology, Department of Viticulture and Enology, University of California, Davis.

·      JENNIFER SMILOWITZ, Associate Director of the Human Studies Program at the Foods For Health Institute at University of California, Davis

·      LARS BODE, Professor in Paediatrics, Director of the Larsson-Rosenquist Foundation Mother Milk Infant Centre of Excellence, University of California, San Diego