A child needs either formula or breast milk for at least the first year of life. Formula and breast milk both provide the necessary nutrition for a baby to grow and thrive; there are several differences between the two substances, however. Breast milk provides a child with many nutrients that formula does not. It is also easier for an infant's body to digest and provides infection fighting antibodies that can greatly reduce the instances of several childhood illnesses. Perhaps the most substantial difference between formula and breast milk is that human milk is a living, ever-changing substance while formula, although similarly nutritional, is not.
Formula is made to resemble breast milk as closely as possible. Researchers have been able to pinpoint and recreate all of the necessary nutrients that a child under age one requires; there are several components in breast milk that simply cannot be recreated in a lab, however, and therefore are not found in formula. A variety of the fats, proteins, and carbohydrates naturally found in breast milk either cannot be synthesized or are too expensive to recreate. Formula is made with similar, but not nutritionally equal, substances. While these still provide the basic ingredients, every major study done between formula and breast milk has found formula to be lacking when compared to human milk.
While both formula and breast milk contain all of the essential ingredients that an infant needs to grow, breast milk is easier to digest. Formula, a man-made product, often includes much more of the different vitamins, minerals, and proteins necessary for development to ensure that the baby absorbs all of the nutrients he or she needs. This means that formula digests much more slowly than breast milk, thus leaving behind excess waste and straining the kidneys and digestive tract. This difference between formula and breast milk is typically most apparent in premature infants and babies born with digestive issues.
Breast milk naturally contains live antibodies to protect an infant from illnesses such as respiratory syncytial virus (RSV), ear infection, and meningitis. When nursing from the breast, an infant, through saliva, sends signals to the mother's body, causing it to create antibodies to any illness that the child is fighting off. Formula does not contain these disease-fighting components. As a result, studies have found that children who are primarily fed breast milk recover from illnesses more quickly and get sick less often than if formula fed.
As long as parents do not change formula brands, a formula fed child receives the exact same nutrients at every single feeding until solids are introduced. Breast milk, on the other hand, constantly changes both daily and during the course of a nursing relationship. In the morning, breast milk is rich in carbohydrates and protein, often appearing watery when pumped. In the evening, however, breast milk is extremely thick, with a much higher concentration of fat. It also contains sleep-inducing hormones late at night, thereby naturally lulling a baby to sleep.
Breast milk also changes as a child grows. In the same way as a baby's saliva signals a mother's body what antibodies it needs, it also tells her body what nutrients the baby needs. Breast milk becomes denser and more rich as a child ages, which means a child who primarily nurses from the breast will only ever need 4 to 6 ounces (120 milliliters to 180 milliliters) of breast milk at a time. Due to the fact that formula stays exactly the same, a child needs more of it as he or she grows to get the same amount of nutrients.