Breast milk composition

A closer look at the composition of breast milk

Feeding for baby |  3 mins reading time

A baby sucking on their mom's breast

The World Health Organization and UNICEF strongly recommends that mothers only feed their babies breastmilk for their first 6 months – starting within 1 hour after birth. A closer look at the composition of breast milk, from that very first colostrum feeding, shows us how intricately balanced the composition of mother’s milk truly is. For protecting, nourishing and preparing baby for the future.

Learning more

Scientific interest in studying breast milk composition is growing – and more and more components are being found. One thing science is discovering, is that one size does not fit all. The composition of colostrum differs from mature milk, and the makeup of mature milk changes from feeding to feeding, and even during a single feed.

In fact, breast milk is believed to be tweaked a bit by mother especially for the needs of her baby.1  For example, when a baby is born preterm, its mother’s milk "tends to be higher in protein and fat."2

On the other hand, studies show3 that the composition of breast milk is not greatly affected by differences in race, age, diet or whether mothers have had previous births.

Protection outside the womb

Evolution has finely tuned mother’s milk to meet the needs of babies. From the very beginning, babies receive a healthy dose of antibodies in colostrum, to immediately protect them as they begin life in the world outside of the womb.

Colostrum is rich in other nutrients - including sodium, chloride and magnesium, as well as vitamin A, C and E. The first week of breast feeding also delivers increasingly higher levels of lipids.

As baby grows

To meet the changing needs of a growing baby, the composition of breast milk shifts as the weeks go by - and nature makes sure that babies get the specific antibodies and nutrients they need to develop.

Bioactive components in breast milk - including immunoglobulin and macrophages - protect babies from infection, boost their immune system, and deal with inflammation2. There are even stem cells, to repair any damage.

A healthy metabolism

From iron, copper and zinc to vitamins A, C, D, E, K and the B vitamins - baby gets a boost of micronutrients early on, starting with colostrum. These are vitamins and minerals that our bodies cannot make (except vitamin D, which is synthesized by the skin from sunlight).

The macronutrients – carbohydrates, protein and fat – make up a large part of breast milk. Of the more than 200 fatty acids present, the majority consists of triacylglycerides, which release energy as they break down. In fact, in there are 3-5g of fat in 100ml of breast milk - which accounts for 40-55% of the calories in mother's milk.

Breast milk also contains over 400 different proteins. The proteins and other macronutrients are essential to the growth of the gastrointestinal tract, and act as a probiotic to promote a healthy gut microbiome - another boost to baby's ability to fight infection and maintain a healthy metabolism. Even into adulthood!

Studies of mother's milk fills volumes, and its intricacies are still being uncovered by science. As we reflect on - and learn more about - the complexities and benefits of breast milk, mothers and their care professionals have a strong basis from which to make to decisions concerning the health of their children.

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Human breast milk: A review on its composition and bioactivity, Nicholas J Andreas, Beate Kampmann, Kirsty Mehring Le-Doare, 2015

Human Milk Composition: Nutrients and Bioactive Factors, Olivia Ballard, JD, PhD (candidate) and Ardythe L. Morrow, PhD, MSc

Jenness R. The composition of human milk. Semin Perinatol. 1979 Jul;3(3):225-39. PMID: 392766

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