The types of human breast milk are classified as colostrum (breast milk in the first week of life) and mature breast milk. The energy content of mature breast milk is higher than that of colostrum.
The protein content of human breast milk is low compared to that of cow's milk (1% : 3%). Human breast milk includes secretory IgA, lactoferrin, peroxidases and lysozymes. These proteins are partly to protect the baby from infection. IgA forms a barrier in the baby's gut to protect against invading bacteria. Lactoferrin serves to deprive any invading bacteria of iron, and peroxidases and lysozymes both have an antibacterial action.
Human breast milk contains about 7% carbohydrate. This, in common with milk from most other mammals, is in the form of lactose.
Fat content in human breast milk is variable during the feed. Initially the fat content of human milk is low and this rises to about 3% by the end of the feed.
The constituents of human breast milk are also modifiable by the maternal diet and well-being, and by the mother's general level of nutrition.
Last reviewed 01/2018