Physiological development of the infant and its implications for complementary feeding.

From the standpoint of nutritional needs, physiological maturation, and immunological safety the provision of foods other than breast milk before about four months of age is unnecessary and may also be harmful. On the other hand, many infants require some complementary feeding by about six months of age. There are a number of known disadvantages and risks involved in too early complementary feeding, including interference with the infant's feeding behaviour, reduced breast-milk production, decreased iron absorption from breast milk, increased risk of infections and allergy in infants, and increased risk of a new pregnancy. With many complementary foods, including undiluted cow's milk, there is also a risk of a water deficit with a resultant hyperosmolarity and hypernatraemia that, in extreme cases, can lead to lethargy, convulsions, and even residual brain damage. Other possible implications include the development of obesity, hypertension, and arteriosclerosis in later life. The decision about when to start complementary feeding depends not only on age but also on the developmental stage of the individual infant, the type of food available, the sanitary conditions in which the food is prepared and given, and family history of atopic disease.