Five things you might not know about breastmilk


Happy World Breastfeeding Week everyone! To celebrate, here are some knowledge nuggets about breastmilk.

1. The milk is not just the milk.

Back when Finley was tiny, I spent almost as much time telling people about breastfeeding as I did actually breastfeeding. Being an Aspie mum, I didn’t always read the room. One time I told my unsuspecting uncle, who has had three breastfed children, the process by which the milk changes when the baby is sick (see point 2). He didn’t even know that the milk changes at all. “I thought the milk was just the milk,” he said.

Angela Garbes puts it best in her article about how amazing breastmilk is: “The nutritional and immunological components of breast milk change every day, according to the specific, individual needs of a baby”.

Breastmilk is not like the cow’s milk in your fridge, which always has the same nutritional make-up, and always tastes pretty much the same, with slight variation over the year according to environmental factors (ask a barista if you would like to know more about that). Breastmilk changes according to the needs of the baby or toddler sucking from the breast

2. The laboratory inside your bra.


In her article, Garbes wonders how it is that her breastmilk adapts to the needs of her sick baby. She learns,

when a baby suckles at its mother’s breast, a vacuum is created. Within that vacuum, the infant’s saliva is sucked back into the mother’s nipple, where receptors in her mammary gland read its signals. This “baby spit backwash,” as she delightfully describes it, contains information about the baby’s immune status. Everything scientists know about physiology indicates that baby spit backwash is one of the ways that breast milk adjusts its immunological composition. If the mammary gland receptors detect the presence of pathogens, they compel the mother’s body to produce antibodies to fight it, and those antibodies travel through breast milk back into the baby’s body, where they target the infection.

This feedback loop(1) is the same mechanism that enables the milk to change according to the needs of the child, not just in terms of sickness but also changing according to the age of the child. For this reason you can breastfeed a newborn and a toddler (called tandem-feeding), and both will get what they need from the milk.

The feedback loop also indicates when a baby is teething. The breastmilk then produces a mild analgesic which soothes the baby’s gums. For this reason babies often breastfeed more when teething. It is also what I told to every single person who said “He’s got teeth now – ouch! Time to stop feeding!”

3. Breastmilk only imbibes that which makes it stronger.

When Finley was only three weeks old, I got sick. Finley did not. It seemed logical to me that since my body was sick, and he was exclusively feeding from my body, that I would be passing on the germs to him.

In fact, the opposite is true. When you are sick, your body produces antibodies. When you are breastfeeding while sick, your body passes the antibodies to your child through the breastmilk, so that she won’t get the same illness you have.

4. Breastmilk helps you and your baby to sleep.

As adults, our circadian rhythms are directed by a hormone called melatonin, which in turn reacts to the amount of sunlight we are exposed to throughout the day and night. According to the Australian Breastfeeding Association, babies don’t develop a circadian rhythm until around 2 months of age, so breastmilk helps regulate the baby’s melatonin levels (2):

Breastmilk has an amino acid (tryptophan) that is used by the body to make melatonin. Tryptophan levels increase and decrease with a mother’s circadian rhythm, so breastfeeding may help develop a baby’s circadian rhythm.

Breastmilk also helps the breastfeeding mother to sleep. Prolactin and oxytocin are hormones released during breastfeeding which can make the breastfeeding mother feel sleepy. For context, these are the same hormones that can make you feel sleepy after sex.

5. Breastmilk changes flavour according to what the breastfeeding mother has eaten.

No joke, one evening I expressed some milk and then I decided to taste it. It tasted like spag bol, which is what I had eaten for dinner. Skeptics have told me that I just thought it tasted like spag bol because I knew what I had eaten, but my claim is backed up by science.

According to the same article, research shows that this exposure to a range of flavours helps the breastfed babies to be adventurous eaters later on:

breastfed infants are more likely to accept new foods, and more likely to have varied diets as they get older. For instance, research suggests that infants are less likely to become picky eaters later in life (Forestell 2017). And the longer babies breastfeed, the more likely they are to consume vegetables during early childhood (de Wild et al 2018).


Happy World Breastfeeding Week everyone!



  1. The feedback loop is one of the ways in which expressed breastmilk is not the same as breastmilk straight from nipple to baby. I’m not opposed to expressing in theory (personally I don’t like doing it and don’t see any advantage for my circumstances) but I object when people talk about expressed breastmilk as if it is the same product as direct breastmilk.
  2. This is another reason why expressed breastmilk is not the same as direct breastmilk. Because I am the obsessive type, once I learned about this, if I did express milk I labelled it with what time of day it was expressed it was as well as the date.

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