Milk Comparisons
There is a common misconception that cow's milk and formula provide infants with the same nutritional benefits as breast milk. This belief is not true; in fact certain components of cow's milk may be harmful to premature or sick infants. While commercial formulas do a pretty good job of trying to duplicate the ingredients in breast milk, they do not match the exact combination and composition because some of breast milk's more complex substances are too difficult to manufacture and some have not yet been identified.
Cow's Milk
Although cow's milk offers some of the same types of nutrients as human breast milk, they are not present in the same proportions, and species-specific differences prevent many of these nutrients from being physiologically effective. Cow's milk can actually cause dairy allergies if given to infants too early in life. In their policy statement "Breastfeeding and the Use of Human Milk," the American Academy of Pediatrics recommends that infants not be given cow's milk during their first year of life. Additionally, the American College of Obstetricians and Gynecologists, the American Academy of Family Physicians, the Academy of Breastfeeding Medicine, the World Health Organization, the United Nations Children's Fund (UNICEF) and many other health organizations recommend breastfeeding only for at least the first six months of life.
Formula
Commercially prepared formulas can be fortified with carbohydrates, fats, minerals and vitamins in an unsuccessful attempt to mimic the main constituents of breast milk. Death rates in Third World countries are lower among breast-fed babies. Breast-fed babies are healthier and have fewer infections than formula-fed babies. Formula-fed infants have more difficulty with digestion than do breastfed infants. Breast milk tends to be more easily digested so that breastfed babies have fewer incidences of diarrhea or constipation. Human milk contains at least 100 ingredients not found in formula.