Breast Milk Composition: Everything You Need to Know About It!

Breast milk is the perfect food for infants. The composition of breast milk can change during a single session of breastfeeding as well as during the whole period of a several months of breastfeeding, being perfectly adapted to the nutritional requirements of the baby.

Breast Milk Composition

Table of Contents


Colostrum has a laxative effect which helps eliminate meconium, the baby`s first stool, helping in establish a good intestinal flora. Because it`s very rich in antibodies, this ensures the baby a natural barrier against infections. After colostrum is finished, the breasts will produce milk with a yellowish color, of a watery consistency, a lot richer in fats and calories than colostrum, but lower in proteins. This is the transitional milk and is a mixture of colostrum and mature milk.

Types of Breast Milk

Towards the end of the 1st week, sometimes even towards the 2nd or 3rd week of breastfeeding, mature milk will be installed. This has a bluish-white color which will become white in the end while the amount of fat from within the milk increases.

The mature milk`s different aspect indicates the fact that it`s consisted from 2 types of milk:

  • Foremilk, which is secreted at the beginning of the feeding. It`s more watery and contains less calories and fats.
  • Hindmilk, which is released while the baby is sucking. This one is richer in calories, proteins and fats, and provides a higher percentage of nutritional substances that the baby needs to develop. The ending milk can appear after a few minutes or even 30 to 40 seconds.

Breast milk is a complete type of food, perfectly adapted to the nutritional needs of the infant, containing not only proteins and fats, but also carbohydrates and water. Through breast milk the mother transmits antibodies to the baby which increase his resistance to various infections.

Breast milk contains 87% water. You don`t need to give any additional water to your baby while breastfeeding. The water helps the newborn to maintain his body temperature. Even during periods with high temperatures, breast milk contains all the water the baby will ever need.

Breast Milk Composition

The characteristics of breast milk recommend it as no other food for newborns. This attribute is due to both nutritional components (fats, carbohydrates, proteins, water, minerals and vitamins) as well as non-nutrients, which contribute to the child`s health and development: antimicrobial factors, growth factors, enzymes and hormones.

The milk composition varies according to a lot of parameters, ranging from broader categories (populations, race) to lesser categories (age, number of pregnancies, lactation period, mother`s diet). Variations in composition are minimal in terms of total amount of macro-nutrients (carbohydrates, fats, proteins, respectively lactose), while nutrition and supplements may influence certain components (fat type, water-soluble vitamins). After the first 6 months, breast milk no longer offers all the required substances to the infant, but in a mixed diet (along with other foods), it can still be able to offer advantages for up to 12 – 24 months. – Read this!

Fats are essential for the development of the baby`s eyes and nervous system, including his brain. Fats represent a big part of the breast milk`s calories. Breast milks contains the following fatty acids:

  • Omega 6 polyunsaturated fatty acids -linoleic acid and arachidonic acid.
  • Omega 3 polyunsaturated fatty acids -docosahexaenoic acid and linolenic acid.
  • Monounsaturated fatty acids – oleic acid.
  • Saturated acids -palmitic acid.

Proteins are included in the composition of every cell. The main protein from milk is albumin, which once reaching the stomach becomes a soft clot that is can easily be digested. The main protein in the cow`s milk is casein, which is a lot more harder to digest and to which some babies have allergies, their organism considering it foreign. Breast milk contain casein as well, but not in such a large percentage as in cow`s milk.

Carbohydrates – their role is primarily energetic. Lactose is the main glucide in the mother`s milk composition (7g/100 ml and 37% of the dry substance), small amounts of oligosaccharides (0.5g/100 ml) completing the carbohydrate component. The amount of lactose is higher in breast milk than compared to cow`s milk for example (3.8g/100 ml), which is why lactose is added to lactose-based formula.

Lactose helps the baby to absorb calcium and once it reaches the intestines, it forms an acid that has the role of maintaining the acid-base balance.

Vitamins and minerals – Breast milk is the ideal combination of nutrients, reason for which it`s also the benchmark for the industrial preparation of “milk substitutes.” However, there`s still a poorly understood nutritional issue: vitamin D deficiency. This breast milk deficit isn`t a single situation, the contemporary nutrition evidencing the deficit of vitamin D in large categories of population: people who living at high altitude, polluted areas or bad weather conditions, people with specific clothing which reduce sun exposure, obese people, people with dark skin, elderly people, people who have diabetes, etc. In line with modern nutrition trends, it has been a few years since the recommended level of vitamin D for children from 200 IU/day, starting with the first 2 months, to 400 IU/day, starting with the first few days. To achieve this, supplements are necessary as breast milk only contains 25 IU vitamin D/liter (dairy production is estimated to an average of 750 ml/day). The possibility of excess of vitamin D by supplementation requires the doctor`s advice on vitamin D administration. – More details!

Vitamin D is an essential vitamin for the development of children, being necessary for the absorption of calcium and its fixation in the bones. Vitamin D, together with vitamins A and C, stimulates and strengthens the immune system.

Both babies that are naturally breastfed and the ones fed with baby formula receive supplements with vitamin D. Depending on the evolution of your baby, a pediatrician will prescribe you the right dosages and forms of vitamin D that you need for daily administration. However, babies are capable to produce vitamin D on their own if they are exposed to sunlight constantly.

Although iron can be found in small quantities in breast milk, it`s presented in a form that is very easy to digest. Most babies born at term don`t need supplements with iron before 6 months old. After that, when the baby`s reserves of iron are finished, most specialists recommend supplements with iron or a baby formula rich in iron.

The milk composition is also influenced depending on the season. During summer breast milk is less fatty and more watery as the baby feels a greater need to hydrate himself. During winter when usually we lose more energy to produce heat, breast milk has more fat in its composition.

In Conclusion

With these observations, the breast milk composition as a whole constitutes a “gold standard” for the production of milk substitutes (baby formulas) and a mandatory reference term when compared to the milk of other species.

Image courtesy of Nature.com

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