Bioavailability of dietary supplements and impact of physiologic state: Infants, children and adolescents

Bioavailability can be broadly defined as the absorption and utilization of a nutrient, both of which may be affected by such host factors as gender, physiologic state and coexisting pathologic conditions. This report highlig hts factors of particular importance for the bioavailability of nutrients f or infants, children and adolescents. Considerations for nutrient bioavaila bility for pediatric populations include maturation of the gastrointestinal tract, growth, character of the diet, and nutritional status. Critical per iods of development include early infancy (0-6 mo), late infancy/early chil dhood (6-24 mo) and adolescence (12-18 yr). Iron, zinc and calcium are mine rals of particular interest and importance to pediatric populations and are susceptible to alterations in bioavailability. In the young infant, iron a nd zinc are highly bioavailable from human milk. By similar to6 mo of age, other dietary sources are needed to maintain continued normal status. In br eastfed infants who were born prematurely or with low birth weight, earlier supplemental iron is often recommended. For the older infant and toddler, iron and zinc are also important for normal growth and development. The bio availability of these trace minerals in complementary foods is discussed. D uring adolescence, adequate calcium intake is critical to normal bone miner alization. In girls, peak calcium absorption and calcium deposition in bone s occur at or near menarche, which illustrates the importance of the physio logic state on mineral bioavailability. Investigations into nutrient bioava ilability must carefully consider these factors, because the failure to hav e well-matched comparison groups with respect to age and/or nutritional sta tus may inadvertently mask differences in nutrient utilization.