Impact of digestion and absorption in the weaning period on infant feeding practices.

Weaning is a transition period in which solid and table foods replace milk or formula. Such a shift involves not only a change in the texture but also the nutrient constituents in the diet of the infant. Appropriate dietary changes, although known to affect the physiologic and biochemical function of the gastrointestinal tract in adults, have not been established clearly in infants. The relationship between diet and gastrointestinal development during the weaning period is explored. New concepts such as alternate pathways for digestion and absorption during infancy and the possible effects of new feeding modalities such as total parenteral nutrition and elemental diet are discussed. The influence of exogenous factors such as malnutrition and diseases on the development of the gastrointestinal function, particularly that of the small intestinal brush border hydrolytic enzymes and exocrine pancreatic enzymes, are also reviewed because of their potential influence on the weaning process.