Breastmilk changes throughout your breastfeeding journey.  The first milk the breasts produce is called colostrum, a thick, yellow tinged milk low in lactose and quantity but high in immunological properties. Colostrum may be low in volume but is thought to be 30 times more potent than the mature breast milk.  Your body starts to produce colostrum around the 20th week of pregnancy but you may not notice it until delivery.  At delivery, once the placenta detaches from the uterus it triggers the process of “your milk coming in”.  This transitioning from producing colostrum and moving to making breast milk often occurs between days three and five postpartum.  During the transition, colostrum will continue to be the primary source of nutrition for your newborn.

What makes up breast milk?

There are two main proteins that make up breastmilk, whey and casein.  The ratio of whey and casein change throughout the breastfeeding journey.  In early lactation, the whey-casein ratio is about 90:10.  The concentration of whey proteins decreases to more like 60:40 in mature milk and continues to fall typically to level out at 50:50 by late lactation.  Weaning milk is lower in volume and is found to have a higher whey content again, back to about 70:30.  During the newborn stage, whey is the main protein present as it is essential to immune development and protecting the mucosal surfaces of the gut.  Casein proteins help support healthy brain development and serve as the major energy source for intestinal health.  Whey and casein proteins are broken down differently throughout the body. Whey protein remain in liquid form when exposed to stomach acid, thereby making it easier to digest.  Casein protein “curdles” when exposed to stomach acid, therefore taking longer to digest. 

When your milk comes in around that day three to five postpartum, the milk changes and becomes a lot higher in volume and looks more milk like, white or even clear in appearance. 

Why does my milk look like that?

There is a wide range of normal when it comes to changes in the colour of breastmilk.  Colostrum starts out that yellow/orange colour and as the transitions to more mature milk happens the colour goes from yellow to white.  The mature milk is made up of a combination of foremilk and hindmilk.  Foremilk is what the baby gets off that start of the feed; it is thinner, lower in fat and is more of a clear or blue colour.  As the feed goes on, the milk transitions into the hindmilk which has a white or cream coloured look as it is higher in fat content. Certain medications and things you eat can change the colour of breast milk.  For example, if you eat a bunch of green vegetables your breast milk might have a green colour to it!  The only change to note is pink, red and/or rusty coloured which could indicate there is blood in your milk.  Think about what you ate, if you had a strawberry smoothie or beets than that can explain the colour but it could be blood in the breast milk which could indicate a problem such as cracked nipples.  Baby is fine to drink that milk but important for mom to reach out to her health care provider and get checked out.

The many colours of breast milk

When you pump and store breastmilk, it can change a little as it separates into layers.  The fat content comes to the surface of the bottle and looks more white or yellow/creamy.  The thinner clear or blueish coloured milk is under on the bottom side of the bottle.  When you are ready to use you want to swirl the milk to get the layers to combine again, do no shake as that can breakdown the properties in the milk.  It is important to note that the colour of breast milk can change after freezing.  Frozen breast milk may look more yellow.  Don’t worry, this is perfectly normal and is safe to give your baby.

The takeaway

You might be surprised to know the varying composition of breast milk and the varying colours!  These are normal processes and it is okay for your milk to change colour.  If you have any questions, please reach out to us and we would be happy to help!

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