The production of milk by the mammary gland follows different phases:

a.      the mammary gland, developing from puberty under the stimulation of the ovarian oestrogen hormone, increases during pregnancy because of the large quantity of oestrogen hormone and progesterone produced by the placenta;

b.      the first liquid produced by the breast, colostrum, is a thick and yellowish liquid which contains protein and lactose but no fat. It is produced from the fifth month of pregnancy, not in a regular way, and constitutes only a hundredth of the quantity of milk which will be produced two or three days after the birth of the baby;

c.      after the delivery, thanks to the presence of the prolactin, following the drop in the oestrogen hormone and progesterone in the placenta, the secretion of colostrum becomes regular because it must feed the baby with the right milk;

d.      the prolactin stimulates the synthesis of a large quantity of fats, lactose and casein from the mammary glands, and the breast begins to secrete a large quantity of milk rather than colostrum. The phase of transition between colostrum and mature milk is called “phase of lactogenesis”. Through a complicated process, the human mammary gland turns glucose into lactose, secretes fats and keeps many proteins with other components, in particular sodium and chlorine.

The composition of human milk is very different from the composition of the mother’s blood:

-         10 times more lactose than glucose present in blood

-         7 times more fats

-         3 times more calcium

-         2.5 times more potassium

-         1/7 of the quantity of protein

-         1/15 of sodium