This is one of my favourite things to explain to parents, because knowing what is really in their milk changes how they feel about every feed. Breast milk is often thought of as simply food, but it is so much more than that. It is a living fluid, alive with cells and constantly changing to suit your baby. Understanding what is really in your milk can be reassuring and, for many parents, quietly amazing. This is a look at what makes breast milk such a remarkable thing.
A living fluid, not just food
Your milk is alive. Unlike anything made in a factory, it contains living cells and is teeming with the ingredients your baby needs, made fresh by your body every day. It is food, drink, medicine and comfort, all in one.
What is in your milk
Your milk carries far more than nutrition. It contains:
- Living white blood cells, which help fight infection.
- Antibodies, which coat your baby's gut and defend against illness.
- Friendly bacteria, which help build your baby's own healthy gut.
- Special sugars called human milk oligosaccharides, which are there not to feed your baby but to feed those good bacteria.
- Enzymes, hormones and growth factors, which help your baby digest, grow and develop.
- Stem cells, whose role scientists are still learning about.
All of this sits alongside the perfect balance of fats, proteins and sugars to nourish your baby.
Milk that changes all the time
One of the most remarkable things about breast milk is that it is never the same twice. It changes to match your baby.
- It begins as colostrum, the thick, golden first milk, small in amount and rich in antibodies. You can read more in Collecting colostrum.
- It matures over the first couple of weeks into your fuller, mature milk.
- It changes within a single feed, starting thirst quenching and becoming richer and creamier as the feed goes on.
- It changes through the day and as your baby grows, always suiting their stage.
- It even responds when your baby is unwell, making more of the cells and antibodies they need.
Made just for your baby
Your milk is uniquely yours, made by your body for your baby. No two mothers make identical milk, and your milk is tailored to your own child, in your own place, at their own stage. That is something no other food can do.
This close working relationship between you and your baby is what shapes your milk, and you can read how it works in How your baby and your body work together.
Get help from your midwife, health visitor or an IBCLC if:
- You are worried your milk is not enough for your baby.
- You are unsure whether your baby is feeding well.
- You want to understand your own supply and how it works.
Call 999 or take your baby straight to A&E if your baby:
- Is floppy or unresponsive
- Will not wake for feeds
- Is having trouble breathing, or their lips, tongue or gums look blue or grey
- Has a sunken fontanelle
- Is visibly jaundiced and unwell with it, for example floppy, hard to wake or not feeding. Yellowing shows most clearly in the whites of the eyes, the gums, and the palms and soles
- Has dark urine or pale, chalky stools
How a consultation helps
Understanding your milk is one thing, and feeling confident your baby is getting it is another. When I see you I make sure your baby is latching and transferring milk effectively and thriving, so you can trust the remarkable thing your body is already doing. Parents often tell me that seeing the evidence, in the nappies, the weight and the swallowing, is what finally lets them relax and enjoy feeding.