Why Are Young Babies Fed on Milk?
Young babies are fed on milk because it is their natural food. The females of all backboned animals whose young are nourished with milk, store this fluid in their breasts, or mammae. The milk of each species of mammal is a complete food for its own young after birth.
Although the same ingredients are present in the milk of all mammals, the proportions differ a great deal. The ingredients are water, protein, fat and milk sugar. Milk protein contains all the essential amino-acids. The fat globules remain enclosed in a soft curd which forms in the stomachs of the young, so that digestion can precede smoothly without the disturbance that fatty foods often cause.
All mammalian species produce milk, but the composition of milk for each species varies widely and other kinds of milk are often very different from human breast milk. As a rule, the milk of mammals that nurse frequently (including human babies) is less rich, or more watery, than the milk of mammals whose young nurse less often. Human milk is noticeably thinner and sweeter than cow’s milk.
Human babies, if not fed by their mothers, may be fed with pasteurized cow’s milk, diluted and sweetened, or a liquid reconstituted from laboratory-prepared dried milk. In various countries babies have been fed on milk from the ass, goat, water-buffalo, reindeer, caribou, sheep, camel, Llama, bitch and mare.
Other foods have been tried. In the 17th Century babies were fed on pap (bread cooked in water) or, as a French doctor advised, bread cooked in beer! After about five or six months human babies are gradually weaned from an exclusive diet of milk and given other forms of nourishment.
Supplemented breastfeeding is recommended until at least age two and then for as long as the mother and child wish. Though it now is almost universally prescribed, in some countries in the 1950s the practice of breastfeeding went through a period where it was out of vogue and the use of infant formula was considered superior to breast milk. However, it is now universally recognized that there is no commercial formula that can equal breast milk.
In addition to the appropriate amounts of carbohydrate, protein, and fat, breast milk provides vitamins, minerals, digestive enzymes, and hormones. Breast milk also contains antibodies and lymphocytes from the mother that help the baby resist infections. The immune function of breast milk is individualized, as the mother, through her touching and taking care of the baby, comes into contact with pathogens that colonize the baby, and, as a consequence, her body makes the appropriate antibodies and immune cells.
At around four to six months of age, the internal iron supplies of the infant, held in the hepatic cells of the liver, are exhausted, hence this is the time that complementary feeding is introduced. Breast milk contains less iron than formula, because it is more bioavailable as lactoferrin, which carries more safety for mothers and children than ferrous sulphate.