Estimation of iron bioavailability in adolescents' meals and snacks.
Dietary iron bioavailability was calculated from 24-hour food records of 224 adolescents. Eating patterns related to high iron bioavailability were identified. Indicators of dietary iron adequacy calculated in this study were the amount of total iron, the amount of available iron, and the percent bioavailability. Mean daily iron intakes were 16.1 mg for boys and 11.1 mg for girls. Estimation of daily iron bioavailability showed that mean available iron from boys' diets, 1.38 mg, and from girls' diets, 0.91 mg, was not only below recommended levels but also below 10% bioavailability, the basis of the RDA for iron. Diets that met recommended levels of available iron had unusually high amounts of energy, ascorbic acid, and animal tissue foods. Patterns of iron bioavailability differed among eating occasions but were similar for boys and girls. The breakfast meal was lowest in the three indicators of dietary iron adequacy; the evening meal was highest. Snacks contributed substantial amounts of food energy but little available iron to the adolescents' diets. If, at each eating occasion, adolescents include foods that enhance iron absorption and foods that are rich in iron, they will increase amounts of available iron in their diets.