I have been breastfeeding for a little over thirteen months now, and it recently dawned on me that I kind of just ‘trust’ the process to work, and have no idea how breast milk is made. This is a rather unnatural situation for me, as I always want to know the ins and outs of everything, so here goes.

First, however, a bit of a glossary of terms:

The Anatomy of the Female BreastAlveoli – a small cluster of cells that produce milk

Areola – the dark bit around the nipple

Ducts – the ‘canals’ through which milk travels down to the nipples. There is one milk duct for every lobe.

Lobule – a cluster of alveoli

Lobe – a cluster of lobules. Each breast contains between 15 and 20 lobes

Milk Sinuses – little straw-like openings on the areola. When the baby suckles it creates suction causing milk to be released from the openings in to the baby’s mouth

Montgomery glands – small bumps on the areola which produce a natural oil that cleans, lubricates and protects the nipple during pregnancy and breastfeeding. This oil contains an enzyme that kills bacteria

Nipples – the bit that goes inside the baby’s mouth

Oxytocin – a hormone released by the pituitary gland when your baby latches on. It causes the muscles around the alveoli to contract and eject your milk down the milk ducts. This passing of the milk down the ducts is called the “œlet-down” (milk ejection) reflex. It’s also this hormone that provides the ‘rush’ of ‘love’ that people sometimes feel during breastfeeding.

Prolactin – also a hormone released by the pituitary gland which causes your alveoli to take nutrients (proteins, sugars) from your blood supply and turn them into breast milk.

How does it work?

When your baby suckles it stimulates the nerve endings in the nipple and areola, which signal the pituitary gland in the brain to release two hormones, prolactin and oxytocin.
The Prolactin causes the alveoli to take nutrients from your blood supply and turn them into breast milk. The milk is produced in the alveoli, which look like a very small cluster of grapes. The pituitary gland releases Oxytocin, which causes the muscles around the alveoli to contract, basically squeezing the milk into the ducts. Each lobe (cluster of alveoli) has it’s own duct, which leads to the areola.

When the baby latches on to the areola and the nipple goes in to the baby’s mouth, the action of baby’s jaw and tongue pressing down on the milk sinuses creates suction. This causes milk to flow through the tiny straw-like openings – the milk sinuses – through the areola and nipple and in to the baby’s mouth.

Important to note

Milk production is continuous, but let-down causes the milk to flow faster. Milk is already there and despite the fears of many mothers-to-be, the cases of there actually not being enough milk are extremely rare.

Linda J. Smith, a highly experienced lactation consultant, writes, “The significant inhibiting factors appear to be (1) breast surgery; (2) retained placenta; (3) Sheehan’s syndrome or pituitary shock; (4) hormonal contraception. If none of those are factors, it’s exceedingly rare than a mom won’t make plenty of milk. Rare situations DO exist, however.”

She also states that milk must be regularly and thoroughly removed from the breast for milk synthesis to keep ‘chugging along unrestricted’.

”Milk retained in the breast downward-regulates total supply to about 15-20% more than the baby takes on an average. The principle goes like this: if more than 80% of the milk is removed, supply increases to maintain the 80-20 ratio. If less than 80% is removed, supply decreases to maintain the 80-20 ratio. Of course this is an oversimplification of a very complex process, but this principle has held steady as new research emerges.”

So the moral of the story: give milk to get milk.

If supply is low, feed as much as your baby is willing, then express or stimulate the nipples. Understanding how the process works should demystify it. Our bodies were made for this and for most of us, it can and does and will work, if we leave it to do it’s thing.

Resources used in the writing of this document:

S.D.Nostrand, D.M.Galton, H.N.Erb1, D.E.Bauman. 1991. Effects of Daily Exogenous Oxytocin on Lactation Milk Yield and Composition. Found at:
Smith, Linda J.
How Mother’s Milk is Made. 1997 Found at:
Breast is Best. How is Breast Milk Made? 2006 Found at:
Mueller, Annie.
How does breastmilk production work? 2010. Found at:


Breast Milk Production: How Is Breast Milk Made?

  1. Hi there, would just like to give you some feedback on above mentioned problem I head.
    So baby had runny, green, frothy poo from 6 – 10 weeks, after 3 visits to GP, a course of antibiotics and a crampy baby. I tried block feeding (keeping babe on one breast for 4 hours) ensuring she empties breast. Well it took a good 10 days, but her stomach has settled, no more cramps, nice mustard coloured poo. And best of all, she only wakes once a night now! Thank you for your advise and help.
    From a happy mommy and baby

  2. This is a very well put together post, and it’s great that you put forth the time to make a post so easy to understand and read. I would love to share this post for others to read. However, I have some concerns. Please don’t think of me as attacking or that I know it all. This is not my intent at all. I hope you understand.

    My concern is the definition of nipple. Nipple is pretty much there to administrate the milk. The nipple is actually way back in the baby/child’s mouth while they are nursing. The baby/child does not latch onto the nipple but the breast area around the areola. If the baby is on the nipple this would cause grave pain to the mother, and less milk or no milk for the baby. Here is a link that will bring forth better understanding of this, since I am not very great with managing words today (I think I am coming down with something, YUCK!): http://www.youtube.com/watch?v=Zln0LTkejIs

    When trying to figure out correct or incorrect latch (if the baby/child is latched on nipple), you look at the mouth shape. If the mouth is formed the same as when one is sucking on a straw, this is incorrect. The mouth needs to be open like a fish, the tongue over the bottom lip and under the breast.

    Please do email me if you decide to edit this piece, and I will share on my Facebook Fan Page. This is the one thing that is missing in my shares.

    Thank you for reading, and again, I don’t mean to offend you in any way.

    PS: For the ladies who need help with breastfeeding information, I would recommend getting help at http://www.kellymom.com. There is a database, along with a forum. They are great!

    1. @Our Sentiments, Hi. Thank you for your comment and for taking the time to share information, it’s appreciated. To be honest, I didn’t spend any time on the nipple as it’s the one part of the breast I felt everyone knows about, but realise that that could hae caused confusion. I have slightly changed the wording in the post to reflect that the nipple goes inside the baby’s mouth, but will leave your comment as is as I think the links might be helpful to others.

      Thanks again for leaving your thoughts and I hope you will feel more comfortable sharing the post now.

  3. Thank you for your advise. I will keep up with the 4 hour on a breast and see how it changes. Learning how milk and breast works really helps, thanks Lusch.

  4. Tanya, yes, that is exactly my experience. The pottying (EC baby) continued to be pretty thin and green for months (though MORE yellow and LESS scummy than before I dealt with the worst of the oversupply issues), and it was only totally normal when she began baby led weaning. Partly because she was very very distractible and so always got more foremilk, partly I suspect just because it takes a while to change back and it was only a month after I changed my breastfeeding habits that she started taking solid food. 🙂

    Oversupply and overactive letdown are usually caused by the combination of a snacky baby being fed on demand (which is NORMAL and GOOD) and mum being told to put baby to the other side every feed (even if feed is only a minute long), or being told that she must feed baby from both breasts at a feeding, or being given misinformation about baby’s signals that they are done (for example being told that the breast is always “empty” when the baby comes away from it) – note, the breast is never “empty”!!

    Advice to avoid oversupply:- feed the baby often, feed the baby at *first cue*, BUT don’t switch the baby around. Feed from one side for a few feeds, unless it is a good twenty minute session. Assume that you are making enough and don’t try to increase supply without very good evidence that you are undersupplying (oops). If you have a baby who latches on only for very short periods, try any trick you have to keep them on longer – including nursing more at night when they are relaxed and sleepy in the dark. 🙂

    Advice to get rid of oversupply once you have it:- get the clocks out and don’t swap to the other breast until four hours is up. Try nursing “uphill” ie with baby on top of you!

    FWIW in my experience most cases where mum thinks she has no milk she is actually suffering from oversupply worsened by helpful advice from professionals who think that breastfeeding is an incredibly trickly technical thing. 🙁 I think most women need to only have this information (ie about how milk is made) when they feel there is a problem – and that there is such a thing as too much advice unless mum is asking for help! Prenatal information is too technical by far, and often too controlling, and post-natal support is insifficient by a long way. Preaching to the choir, I know. 😉

    1. @Sarah, Awesome response Sarah! Thank you! So helpful and informative. I must say, since learning how the milk is made I feel so much … excitement. I love knowing that it’s THERE and let down is what makes it come out. If that makes sense. It’s made pumping for the milk bank so much easier, as I now get Kyra in on the action and get so much more milk! Loving how our bodies are perfectly and wonderously made! 🙂

      1. @Luschka, Thanks, and I agree – it is a frankly astonishing system! Having my baby on the other side was the only way I could express for my friend’s son, I’ve never been able to pump much in one go but I met half his milk needs for three months until he could be fully breastfed. *heart* Great times!

    2. Hello, I know this is an old post, but I’m having the same problem, plus my 8week old gets very agitated now due to a forceful letdown. We’ve been breastfeeding with ease up until a week ago. He has gained a pound every week of his existence, but now I think I may have an oversupply from so much on demand feeding. I’m not positive that I have an oversupply, but I definitely have a fire hose letdown…
      Should I try the block feeding? His poo is green ever since he’s been crying at the breast in frustration. Sometimes he cries so hard I can barely console him, and he is afraid to relatch. He isn’t in pain though…
      Up until a week ago his poo was a nice brown, mustard color….

      1. Hi Sarah. I would suggest getting in touch with a lactation consultant as I can’t say just from these details, however, something that did help for me was expressing a little to ‘take the edge off’, but the problem with that is that you could be increasing the supply, which doesn’t help the situation (although you could give baby the bottled milk which means your breasts should produce less over time). Remember around now your milk reservoire will dry up and it’ll become supply and demand too, so it’s constant change. Hang in there, it does become more intuitive.

  5. Does anybody know of the foremilk, hindmilk imbalance that cause baby to have green, runny, frothy, explosive poo? My 10 week old started with a runny tummy at 6 weeks. Been to dr weekly since then. At first they said gastro, now its allergic to my breastmilk? what? This is my 3rd baby i’m breastfeeding. Then I read on breastfeeding ass australia about milk oversupply(which I do have) and the imbalance. They suggest block feeding on one breast for 4 hours before swopping breasts. Since doing thid,Baby is calmer, sleeps better and no cramps, but still the runny poo! Anyone no about this?

    1. @Tanya, Yes, Tanya, same happened with my daughter. She had the same green explosive poo and yes, feeding till she gets to hindmilk is definitely the best thing to do. I doubt the ‘allergy to breastmilk’ theory. If you have no allergies to nuts in your family, what I would recommend is what I did (and this is contrary to pretty much all advice you’ll get, but it did work for us) is to have a teaspoon of peanut butter about 15 minutes before you’re going to feed. Peanut butter is a carboloader, so it increases the calorie content of the milk almost immediately. I went through about five tubs of peanut butter in the first couple of months and it definitely helps, but do make sure there’s no nut allergies, as it does go through in the milk. Best of luck! Let us know how you get on.

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