The Science of Human Milk: Meet Sarah Brennan

Dr. Sarah Brennan (@stabrennan), NUI Galway, will be taking part in Soapbox Science Galway on 29th June with the talk:“The Marvels of Human Milk”





by Sarah Brennan

The Science of Human Milk is pretty fantastic. As a GP and a lecturer in a medical school and having 5 children I have learnt so much about breastfeeding and human milk that I feel it is so wonderful that I have to share it. There are hundreds of substances in Human Milk that feed our babies while helping keep them be healthy and grow optimally.

In each drop of milk there are up to a million cells-all the cells that are in our blood are in milk with the exception of Red Blood cells-and this is why human milk is commonly referred to as ‘White Blood’. In 2007 Australian scientists discovered that human milk contained Stem Cells, cells that when stimulated can change to become any tissue in the body such as bone, fat, liver and brain cells as well as many more, and which are used to help kids recover from chemotherapy treatment for Leukaemia. Scientists around the world are busy trying to find out why we feed Stem Cells to our babies. They have found out, by studying animal studies, that after the baby animals drink their mother’s milk that contains stem cells too, the cells can be later found in the baby animals’ brains! This is really brilliant as it help us understand that the stem cells in our milk are probably going into our baby bodies and helping to replace and repair any problems that occurred while they were being made in our wombs.

In each drop there are also up to a million microbes – bacteria, fungi and viruses. You would think yuck, but actually these are all friendly and ones which our bodies depend on, to make our microbiome in gut which helps our body function properly. This Microbiome was only a recently discovered as an Organ in the body and it weights around 1 kilo in an adult, that’s the same as a bag of flour! Lots of research is happening in this area and recently people have been talking about how when our gut bacteria are healthy so is our brain and our mental health. You may have heard about the ‘Gut Brain Axis’: well this is exactly the same thing, when our guts are happy so are we! Interestingly our Human Milk not only contains perfect food for our babies it also contains perfect food for all the bacteria! We have over 200 different types of sugars, called, very fancily, ‘Human Milk Oligosaccharides’ or HMOs in our milk. Most of these HMOs the babies can’t absorb as food at all but the bacteria and fungi can! It is like buying a gold fish and getting the fish food with it for free. We supply loads of healthy bacteria, living organisms to our babies, and in order to keep the bacteria healthy we supply the food for them too. Recent research has also shown that theses sugars help protect our babies from infections and diarrhoea and even constipation!

The next cool thing in milk is Human Alpha-Lacto albumin. When our babies drink this it interacts with the babies  stomach acids and Oleic Acid and changes into HAMLET [ which stands for this Human Alpha-lactoalbumin Made lethal to Tumor cells!] a substance which can kill abnormal and cancer cells. This was discovered in 1990’s and is currently being tested for use as a medicine to fight cancer, how cool ‘cancer drug discovered in mother’s milk’. So like the stem cells, scientists think the babies drink it, it then changes into HAMLET and if it finds any cells that are abnormal or could become cancer cells, attaches to them and makes them die, thus reduces the risk of getting cancer. This fits with studies that find that babies who breastfeed have a lower of leukaemia and other childhood cancers.

Finally, let’s talk about Oxytocin: the hormone that we produce when we fall in Love. Well this is contained in our milk too. When we feed our babies we also get a rush of oxytocin into our own bodies and we are filled with a feeling of contentedness and love for our baby. This helps us to bond to our babies and also helps our babies feel love through the milk and in feeling love the feel safe and protected. It is really important for babies to feels protected. When they feel this way they grow up to become confidence and happy adults. When we exam the science of oxytocin we see that it helps to reduce stress in our bodies by lower Cortisol, that if elevated all the time can be very toxic and damaging to both the baby and the mother. It also opioids in the baby, which are pain relieving substances like morphine! So that if our baby gets hurt or is getting vaccinated it is a great way to help them manage their pain.

So if you are interested in more, here is a cool infographic all about these and other cool components of human milk




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