Absolutely. The composition of breast milk changes throughout lactation to meet the specific needs of the infant, at each stage of its development.
Long before breast milk is produced, colostrum, a concentrated liquid excreted in small quantities, is produced in the first days after the baby is born. Rich in protein, vitamin E, β-carotene, zinc and immune substances (antibodies), this “first milk” helps the baby fight infections and contributes to the maturing of the digestive system.
Next comes the production of breast milk in greater quantities, commonly known as “lactation”. During this period, milk production evolves from a transitional milk, which still contains colostrum, to mature milk. A mixture of colostrum, transition milk and mature milk is present between the first and second week after delivery. This transition brings a progressive dilution of milk which, when mature, is less concentrated in vitamins, minerals and energy.
Besides changing throughout breastfeeding, breast milk also changes depending on the time of day, partly because of hormonal rhythms, and during the feeding itself. For example, when baby starts to suckle, the milk is made of water and sugar. As the baby suckles, the milk becomes more fatty and high in protein. The composition of commercial infant formula (CIF) obviously does not have this adaptability.
CIFs use mature breast milk as a reference: companies that produce them try as much as possible to reproduce the components. However, there are several differences between the two (French only).
Health Canada and the World Health Organization recommend exclusive breastfeeding for the first six months of life and continued breastfeeding with complementary foods for two years or more.