Milk supply: How does it work?

My milk supply worries

When I first started learning about breastfeeding, one of the questions that most intrigued me was milk supply: how much milk does the breast make? How much does the baby need? How do you know whether the breast is actually making enough – can you measure it somehow? Of course, as a dietitian, I was used to measuring everything in millilitres and grams and calories; the fact that I couldn’t do so with breastmilk was more than a bit unsettling!

Fortunately for me, I answered all those questions before my own children were born. Can you imagine trying to breastfeed while worrying about all those things? Actually, perhaps you can – I’ve heard so, so many women worry about whether they are producing enough milk or what they should be doing to make sure their milk doesn’t run out. Some women (and their doctors!) get so worried about this that they end up expressing and bottle feeding, and miss out on all the joy and ease of breastfeeding.

Here’s what I learned that changed the game for me: I learned that breast milk production is very closely regulated by the body; that the brain, breasts and hormones all work together to ensure that there is always enough milk – not too little, and not too much. I learned to trust in nature and my instincts. I also learned that measuring breastmilk in precise amounts is not particularly useful, since the milk composition is constantly changing. And I learned that as long as the baby is thriving, the precise volume of breastmilk he’s drinking doesn’t really matter.

What determines how much milk is made?

For me, one of the most helpful and reassuring things was when I finally understood how milk production works.  Once I understood the system, I was able to relax and trust my body to get it right. In a nutshell, it works like this: supply and demand. The baby (or the pump) creates the demand and the breast ensures the supply to meet the demand.

Milk supply infographic

So, that explains it all, right? No, I thought not. Unfortunately, that’s the explanation moms usually get given, and it may leave you feeling even more confused than before! After much thought, I’ve found a way to explain it to myself by analogy. I compare the breast to a bakery: (why a bakery? Because there’s a big Sasko bakery near my house, so it was the first kind of factory that came to mind. But it turned out to be a very accurate metaphor). Like a bakery produces bread, the breast produces milk. Both require certain inputs: the bakery requires flour, yeast, water and so on; the breast requires the nutrients, water and hormones that are in the blood. Both require certain equipment: a bakery needs ovens, and a breast needs milk cells (these are the glands that actually turn blood into milk).

What determines how much bread (or milk) is made? For a bakery, it depends on how much bread is ordered by the customers: if they have orders for 100 loaves, that’s how many loaves they’ll bake. As long as they don’t run out of ingredients and the ovens are still working, they will produce exactly as many loaves as were ordered. The breast is exactly the same, only in this case the orders are placed by removing milk from the breast. So if baby is settled, drinking more or less the same amount each day, your milk production will stay more or less constant, providing exactly as much milk as baby is asking for.

Increasing and decreasing milk production

And what happens when the “demand” changes? If the bakery suddenly gets more orders, they simply start baking more loaves. Assuming they have enough ingredients and the ovens are still working, they will have the larger order filled before the end of business. In the same way, if the baby drinks all the milk in the breast and is still sucking, the rate of milk production increases – and it increases immediately. The milk responds to changes in the baby’s demand very quickly.

On the other hand, if our bakery bakes 100 loaves but customers only collect 60, and this happens for a few days, they will soon downscale to only baking 60 loaves a day. Just so in the breast: if baby drinks only a little milk, and the breasts are often full, the breast will start making less milk.

Increasing a low milk supply

The whole bakery analogy is very useful for understanding what we do when we try to increase milk supply. Imagine at our bakery that the top management decides that they need to sell more bread, so they immediately double the amount of flour that they buy. Meanwhile in the kitchen, the bakers are still only baking as many loaves as the customers ordered. If management wants them to sell more bread, they need to find more customers!

It seems so obvious when we talk about baking bread, but when a mom is struggling with low milk supply, we usually do the same thing: she immediately gets prescribed a pill (or perhaps a homeopathic remedy or herb) for increasing milk production. But these substances (called galactagogues) work by increasing the levels of hormones that stimulate breast milk production. So it’s like buying flour for the bakery: unless your initial problem was a lack of flour, buying more flour will not cause more bread to be baked! Instead, we need to increase the number of orders coming in. For a bakery, this means finding more customers, or getting existing customers to buy more bread. For breastfeeding, it means we need to empty the breast more thoroughly, more often – whether that be by addressing a poor suck, feeding baby more often or by pumping. We will look at the details of how to increase breast milk production in another post, but I just wanted to show you how much sense it makes to look at your breast as if it were a bakery.

Bespoke manufacturing

Of course, there’s one way in which a breast is unlike a bakery or any other commercial enterprise: breast milk is absolutely tailor made from moment to moment. That would be like a bakery baking bread to a specific recipe for each customer, and moreover a recipe that changes every day and that the bakery automatically adjusts based on the customer’s health status at a given moment. And yet your breasts do that without you having to give it a second thought. Isn’t nature wonderful? When I got to this point in my learning, I realised that my body does a much better job of knowing what my baby needs than I ever could, and I was perfectly happy to just let things be!

What does this mean for you?

So to recap: your breast knows how much milk to make by the amount of milk you take out of it. Take out more milk, and your breast will make more milk. Leave the milk in the breast, and the breast will make less milk. Assuming all your “machinery” is working well (and it is in some 95% of women), it really is as simple as that! So relax, feed your baby as much as he wants, and trust nature’s system to work, as it has done for billions of years.

If you are still worried about whether you have enough milk, check out this post to learn what are the signs of a good milk supply, and this post to learn which things you needn’t worry about.

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