Special Considerations for Infant Formulas

With the exception of exocrine pancreatic function and bile acid metabolism, the gastrointestinal tract is anatomically and functionally fully developed in infants born at term, and dietary contents do not influence their development. Trophic factors can be found in human milk and in the gastrointestinal tract, but their function is unclear. As these factors are more fully identified and their structure, composition, and physiological effects understood, it is possible that one or several may have effects on infant organ systems. 

Similar to the gastrointestinal tract, development of renal function is not influenced by dietary content. Glomular filtration does not approximate adult values until about 3 years of age, and tubular reabsorption and urine acidification reach normal values at several months of age. However both are sufficient for healthy term infants, but contribute to fluid and electrolyte abnormalities in infants who are ill and in those who are fed an inappropriate diet. 

The infant immune system is not fnlly mature at birth it has deficits in the ability to prevent invasion of pathogens and to respond to antigens. Of particular concern in the context of ingredients new to infant formulas is the increased permeability of the gut mucosal barrier in the presence of inflammation or infection or if the integrity of the epithelial cell layer is disrupted. The increased permeability allows macromolecules to be absorbed, which stimulates allergic responses to food proteins. 

Most of the principles that govern the safety of ingredients new to infant formulas derive from the same principles that govern food safety for older children and adults. The committee concluded that the six issues described below and summarized in Box 2-1 must be considered as important safety issnes when regnlating infant formnlas. 

Infant formulas are the sole or predominant source of nutrition for many infants. Even for infants for whom formulas are a supplement to hnman milk, formulas can consti-tnte a major source of nutrition. For infants, formulas represent a mnch larger percentage of the total nutritional intake than is any single snbstance for the older child, adolescent, or adult. Given the extremely high dependence on this one sonrce of dietary input, safety rules based upon models deemed appropriate for persons with a wide range of dietary inputs may be inappropriate. 

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