Aptamil Research
Aptamil Research

The Composition and Functions of Breast Milk in Detail

Breast milk is the healthiest food for your baby and plays an enormous role in their healthy development. Its secret is its ingenious and unique composition.

Breastfeeding is best for your baby, because the natural compositon of breast milk is unbeatable. Its composition adapts to the changing needs of your baby and provides them with precisely the nutrients their body needs for each stage of growth. Let’s take a closer look at the composition of breast milk.

The most important components of breast milk:

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  1. An age-appropriate quantity of high-quality proteins ensures healthy growth and a lower risk of obesity in later life.
  2. Prebiotics support healthy intestinal flora and the immune system.
  3. Lactose, or ’milk sugar’, supplies your baby with energy and is a very important constituent of breastmilk.
  4. The fats in breast milk are significant energy sources for your baby. The long-chain polyunsaturated fatty acids (LCPs) are extremely important. Newborns’ bodies cannot produce LCPs in their first months of life and depend on breastmilk as a source.  

Composition of breast milk: The sizes of the individual components does not correspond exactly to the quantity in the breastmilk.

Lactose and indigestible “prebiotic” carbohydrates


Breast milk contains carbohydrates in the form of lactose (milk sugar) and indigestible, prebiotic oligosaccharides. On average, lactose accounts for just under 40% of your baby’s daily energy supply.  It contributes energy, supports the absorption of calcium and is important to healthy intestinal flora, as it inhibits putrefactive bacteria and stimulates the growth of bifidobacteria.  Breast milk contains nearly twice as much lactose as cow’s milk — approximately 7 grams per 100 millilitres, depending on the age of your baby.


Why is the dominance of bifidobacteria in a baby’s intestinal flora so important?

Bifido-dominant intestinal flora can protect babies from infections and allergies. Bifidobacteria produce acids to create an acidic milieu in the intestines that inhibits the growth of pathogenic bacteria. The colonisation of the intestines with bifidobacteria stimulates the overall development of a strong immune system.

A miracle cocktail with a protective effect on the baby

The indigestible carbohydrates in the breast milk remain fully intact during passage through the gastrointestinal tract, as they are not digested by the enzymes of the intestinal tract, and reach the large intestine undigested. There they stimulate the growth of health-promoting bacteria, and bifidobacteria in particular. Scientists speak of the “prebiotic properties” of the oligosaccharides. Bifidobacteria are thus dominant in the intestinal flora of breast-fed babies.


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Mature breast milk has a very high fat content, averaging 4.03 grams of fat per 100 millilitres. Its fat content supplies 40 to 50 percent of your baby’s daily energy supply. In contrast to cow’s milk, breast milk has a higher proportion of polyunsaturated fatty acids. The essential fatty acid, linoleic acid, accounts for 10% of the total fatty acids in breast milk, whereas cow’s milk contains only approximately 2 percent.

LCPs support the development of the brain, nervous system and vision

Brain food: LCPs

Long-chain polyunsaturated fatty acids (LCPs) are essential building blocks for the brain, particularly in the first 1000 days of life. Children who have a good supply of LCPs develop better cognitive abilities than children who do not receive an adequate supply of LCPs.

In addition, 100 millilitres of breast milk contains an average of 13.5 grams of valuable long-chain polyunsaturated fatty acids (LCPs). LCPs are important building blocks in all cell membranes, with particularly high concentrations in the cell membranes of the brain, nerves and eyes. That means that LCPs are extremely important in the development of the brain, nervous system and vision.


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The protein content of breast milk is roughly 0.8 to 1.2 grams per 100 millilitres. This is very low in comparison to cow’s milk and is perfectly adapted to your baby’s needs.  The metabolic and digestive system in babies are too immature to cope with high amounts of protein. A high protein content would overtax their metabolism. During the breast-feeding period, the protein content drops, It is considerably higher in the colostrum immediately after birth than in the mature breast milk later. The two main proteins in breast milk are whey and casein. Their ratio changes from 80:20 in colostrum to 60:40 in mature breast milk.



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Breast milk contains all of the important vitamins your baby needs in ideal balance: Vitamin A, essential for growth and development and for healthy skin, vision and a properly functioning immune system. Vitamin E supports the metabolic processes and protects polyunsaturated fatty acids (LCPs). Breast milk also supplies the water-soluble B-complex vitamins and vitamin C in age-appropriate quantities.

Breast milk also contains vitamin D, but not in sufficient quantities.  That’s why giving both breastfed and non-breastfeed babies a vitamin D supplement from the end of the first week after birth to the end of the first year is recommended to prevent rickets. This supplement should also be continued in the winter months of the child’s second year as well.


Minerals and trace elements

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Calcium (Ca) and phosphorus (P) are important minerals for the mineralisation of your baby’s bones.

Trace elements belong to the group of anorganic minerals. They are called trace elements because they occur — and are needed — in minute quantities (traces). Iron (Fe) is important for the production of red blood cells and brain development. The protein lactoferrin in breast milk supports the absorption of iron. Other important trace elements include selenium (Se), which protects cells against attacks from free radicals, as well as chromium (Cr) and zinc (Zn), which are involved in various growth and metabolic processes.

Other components

The nucleotides are also worthy of mention. Nucleotides are the building blocks of the nucleic acids: DNA, which carries our genetic information, and RNA, which is responsible for protein biosynthesis. During periods of rapid growth, such as in early life, the body’s normal nucleotide production is insufficient and a food source is required. That’s why the nucleotides in breast milk are so important for the baby.

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Always there for you!

Contact our Aptacare expert team. Our experts are nutritionists, midwives and pediatric nurses, and all of them are mothers too. Specially trained breast-feeding experts will be happy to advise you on all your questions regarding breast-feeding.

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