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Breastfeeding Advisor

Components of breastmilk

Take a look at the contents of breastmilk, which change over time.

Breastmilk has various advantages, one of which is that it contains well-balanced nutrients, including fat, lactose and protein, which are the main ingredients. The proportions of these ingredients are automatically adjusted at different times to match the growth of baby. This makes breastmilk the best food for your baby.

Breastmilk components and their functions

Fat, lactose and protein, the main components of breastmilk, have the characteristics below. Lactose is a source of energy and is contained the largest proportion (among fat, lactose and protein) in breastmilk.
Fat is an important ingredient in the development of your baby's brain and in the maintenance of the body structure.
Protein is broken down into amino acids when it is absorbed into your baby's body, and becomes a source for building muscles. It also contains important immunoproteins such as lactoferrin and IgA.

Other components have the functions explained below.

  • They reduce the risk of allergies developing
    Breastmilk has a substance that forms a protective coating on the intestinal wall, and promotes the development of the intestinal epidermis. Thus it prevents allergens from invading through the baby's intestines, which have numerous openings.
  • They help breastmilk be easily digested and absorbed
    Breastmilk contains enzymes such as lipase and amylase that help with digestion, so it is easily digested and absorbed by babies with fragile intestinal systems.

Change in breastmilk components

The components of breastmilk change according to different factors, including the number of days postpartum, the season and the mother’s diet. The composition of breastmilk changes each time your baby nurses, and even changes as your baby is nursing. Here is how the components change according to the number of days postpartum and with each breastfeeding.

Change of components in one breastfeeding

The breastmilk released each time your baby begins breastfeeding is called fore milk, and this is followed by hind milk. As breastfeeding continues, the fat content, which is a source of energy and is important for the development of the brain and the maintenance of the body structure, increases.

Conditions: Express breastmilk using a Pigeon Electric breast pump 5 times, 10 ml each. 5 ml of each sample was dispensed into test tubes, and centrifuged (3,000 rpm × 5 min.)

Change in breastmilk components according to postpartum date.

Breastmilk is separated into two main groups, colostrum and mature milk.
Colostrum is the breastmilk secreted until the fifth postpartum day. It is characterized by the large content of immunoproteins, such as lactoferrin and IgA. This breastmilk looks yellow because it contains β-carotene, which is also found in carrots and other vegetables.
Mature milk is the breastmilk that is secreted 10 days postpartum. It is characterized by a lower protein content and higher content of lactose and fat as compared to the colostrum, making it higher in calories. Breastmilk at this time looks milky white.

As stated above, breastmilk is a nourishing food that only mother can produce.
Breastfeeding in infancy helps babies grow healthy in all the best ways.

Postpartum date
Time course of breast milk contents Indicated by relatove values, contents of 3rd-5th postpartum date as 100%.

Refferense:Itoda et al., 1991, Japanese Journal of Pediatric Gastroenterology, Nutrition 5(1), P145-158


Human breastmilk has the highest content of lactose and the lowest content of protein.
Seals and whales that live under rough conditions in the ocean, in polar regions or in the desert, are generally said to produce breastmilk with a very high fat content, much higher in fat than that of dogs, pigs and humans, which have longer breastfeeding periods.

Chart 3.2 Breast milk compositions of each mammal (%)

classification animal solid content fat protein lactose mineral
Animals which have longer breastfeeding priods rabbit 36.9 18.2 13.9 2.1 1.8
mouse 29.3 13.1 9 3 1.3
dog 23.5 12.9 9 3.1 1.2
pig 18.8 6.6 5 5.5 0.6
Animals which feeds according to baby's demand human 12.4 3.8 1.5 7 0.2
horse 11.2 1.9 2.5 6.2 0.5
cow 12.7 3.7 3.1 4.8 0.7
monkey 15.4 4 1.6 7 0.2
Animals under rough conditions mole 35 20 10 0.1 0.8
seal 65.4 53.3 8.9 0.5 0.6
whale 57.1 42.3 11 1 1.4
polar bear 47.6 33.1 10.9 0.3 1.4

Referrence:Shuichi Ueno, 1997, Science of breast milk, P19

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