Milk in Infancy and Childhood: Nutrition and Allergies

In the middle of the 20th century, when nutrition was thought to be a simple matter of protein, calories, vitamins, and minerals, cow’s milk seemed a good substitute for mother’s milk: more than half of all six-month-olds in the United States drank it. Now that figure is down to less than 10%. Physicians now recommend that plain cow’s milk not be fed to children younger than one year. One reason is that it provides too much protein, and not enough iron and highly unsaturated fats, for the human infant’s needs. (Carefully prepared formula milks are better approximations of breast milk.) Another disadvantage to the early use of cow’s milk is that it can trigger an allergy. The infant’s digestive system is not fully formed, and can allow some food protein and protein fragments to pass directly into the blood. These foreign molecules then provoke a defensive response from the immune system, and that response is strengthened each time the infant eats. Somewhere between 1% and 10% of American infants suffer from an allergy to the abundant protein in cow’s milk, whose symptoms may range from mild discomfort to intestinal damage to shock. Most children eventually grow out of milk allergy.