Infant formula is produced to support the adequate growth of infants under six months of age when fed as a sole source of nutrition.
• The composition of infant formula is based on a mother's milk at roughly 1to3 months postpartum.
• The most widely used infant formulas contain purified cow's milk whey and casein as aprotein source, a blend of vegetable oils as a fat source, lactose as a carbohydrate source, a vitamin-mineral mix, and other ingredients depending on the manufacturer.
• There are many infant formulas using soya bean as a protein source in place of cow's milk and formulas using protein reduced into its component amino acids for infants who are allergic to other proteins.
• An upswing in breastfeeding has been accompanied by a deferment in the average age of introduction of other foods (such as cow's milk), resulting in increased use of both breastfeeding and infant formula between the ages of 3–12 months.
Infant formula is necessarily an imperfect approximation of breast milk because:
• The exact chemical properties of breast milk are not fully understood.
• A mother's breast milk changes in response to the feeding habits of her baby and over time, thus adjusting to the infant's individual growth and development.
• Breast milk includes a mother's antibodies that help the baby avoid or fight off infections and gives his immature immune system. The mother's immune system has many years of experience with the germs common in their environment.