Medically reviewed by Alyssa Copeland, RN, IBCLC
One of the most amazing things about breast milk is that it’s always changing. From the time your baby is born to the time you wean, it’s constantly changing to meet your baby’s needs. In this post, you’ll discover the 4 incredible ways your breast milk changes..
- during a pumping session
- throughout the day
- as your baby grows
- when your baby gets sick
Disclaimer: The information on this website is for informational purposes only. You can read my full disclaimer here.
1. Breast milk changes during a pumping session
During a pumping session, your breast milk gets progressively fattier. You start out getting the more watery foremilk, and towards the end of your session, you’ll get the fattier hindmilk. This is why it’s so important to empty your breasts, so that you’re getting all the fat content out.
But foremilk and hindmilk aren’t actually different types of milk. Breast milk is breast milk.
The reason why your milk is fattier towards the end of a session is that the fat separates inside your breasts, similar to the way it does in a bottle when stored.
The longer you go between pumping sessions, the more of a difference there will be in the foremilk vs hindmilk. This is because the fat will have had more time to separate.
2. Breast milk changes throughout the day
The levels of different hormones, vitamins, etc vary throughout the day. Morning and daytime milk contains certain things that help your baby stay alert and active. Evening and nighttime milk contains things that help promote sleep.
Morning milk has higher levels of
- cortisol, the hormone that causes alertness
- magnesium, zinc, potassium, and sodium
Daytime milk has higher levels of
- iron, which peaks at noon
- activity-promoting amino acids, such as tyrosine, which helps with attention and focus.
- antibodies, C3 and C4 proteins, and phagocytes, which are all part of the immune system
Evening milk has higher levels of
- melatonin, the hormone that causes drowsiness
- total fat content
- vitamin E
Nighttime milk has higher levels of
- melatonin, which starts to rise in the evening and reaches the highest levels around 3 AM.
- leptin, which controls appetite and signals your brain to stop eating.
3. Breast milk changes as your baby grows
The composition of your breast milk also changes the longer you breastfeed to meet your growing baby’s needs.
First 2-4 days: Colostrum
- Thick, yellowish, low volume
- Higher in protein and antibodies
- Natural laxative and can help prevent jaundice
From 4 days to 2 weeks: Transitional Milk
- Mix of colostrum and mature milk
- High levels of fat, lactose, vitamins and more calories than the colostrum.
From 2 weeks on: Mature Milk
- Thin, white, higher volume
- Higher in fat and carbohydrates
- Contains 90% water to keep baby hydrated.
Mature milk also changes.
Mature milk from the newborn stage will be different from milk at 6 months or 1 year. A recent study on prolonged lactation showed that as your baby gets older, carbohydrate levels in breast milk decrease, while fat, protein, and energy content continue to increase.
4. Breast milk changes when your baby is sick
When you or your baby gets sick, your body makes antibodies that are transferred to your breast milk. This is probably my favorite thing about breastfeeding and why I decided to continue to breastfeed my kiddos past 1 year.
- If you get sick, your body will make antibodies to help protect your baby from getting sick.
- If your baby gets sick, your body will make antibodies to help your baby fight off the infection.
There’s one theory that suggests that when a sick baby nurses at the breast, the baby’s saliva enters the nipple through “backwash”. This exposes the mother to the baby’s germs, so her body can make the antibodies her baby needs.
But this isn’t the only way. You don’t need to be directly nursing for your baby to get the same benefit. If your baby is sick, chances are you’ve been exposed to the same germs from being in close contact with each other. So by kissing your baby, snuggling, and doing skin-to-skin, you’re exposed to your baby’s germs and your body will make the antibodies your baby needs.
Breast milk is truly incredible in how it’s tailor made to fit your baby’s needs at every stage and circumstance. What an amazing gift you’re giving your baby by exclusively pumping!
You are doing an amazing job!
P.S. Exclusivey pumping is TOUGH. If you’d like some tips and hacks to make it easier, I’ve created a FREE cheatsheet of the Top 12 Game Changers for Exclusive Pumping. Click here to download it!
This post has been medically reviewed by Alyssa Copeland, RN, IBCLC
Alyssa Copeland is a mom of 3. She is a graduate of University of Michigan School of Nursing, and has been a pediatric RN since 2010. She has been an active La Leche League Leader since 2016 and an IBCLC since 2020.
Sources:
https://www.foundmyfitness.com/episodes/breast-milk
https://findyourmomtribe.com/foremilk-hindmilk-imbalance/
https://www.llli.org/breastfeeding-info/foremilk-and-hindmilk/
https://www.mattoslactation.com/blog/2019/2/11/the-foremilkhindmilk-misconception
https://www.sciencealert.com/human-breast-milk-composition-may-help-babies-tell-time
https://parentingscience.com/breast-pumps-and-baby-formula/
https://www.nature.com/articles/s41390-019-0368-x?proof=t%2Btarget%253D
https://www.hormone.org/your-health-and-hormones/glands-and-hormones-a-to-z/hormones/leptin
https://www.ncbi.nlm.nih.gov/books/NBK501863/
https://www.healthline.com/nutrition/tyrosine
https://lacted.org/questions/0123-breastmilk-prolonged-lactation/
https://www.mdpi.com/2072-6643/10/12/1893/htm
https://www.hellomotherhood.com/article/496122-colostrum-and-the-stages-of-breast-feeding/
https://parentingscience.com/calories-in-breast-milk/
https://www.mdpi.com/2072-6643/11/12/2842/htm
https://www.verywellfamily.com/colostrum-the-first-breast-milk-431990
https://exclusivepumping.com/exclusive-pumping-questions-lactation-consultant/
