menstrual iron losses in adolescent girls (aged 14 through 18 years).
In this model, no provision was made for the development of iron stores after early childhood. It is accepted that all recognized functions of iron are met before significant storage occurs and that stores are a reserve against possible future shortfalls in intake rather than a necessary functional compartment of body iron. Because most individuals in this age group in the United States and Canada are believed to consume iron at levels above their own requirement, it can be assumed that most will accumulate some stores.
The major physiological event occurring in this age group is puberty. The associated physiological processes that have major impacts on iron requirements are the growth spurt in both sexes, menarche in girls, and the major increase in hemoglobin concentrations in boys. Because the growth spurt and menarche are linked to physiological age, the secular age at which these events occur varies among individuals. The factorial model distorts this by using averages. Since the growth spurt and menarche can be detected in the individual, provision is made for adjustments of requirement estimates when counseling specific individuals. These are addressed later under “Special Considerations”.
Estimation of the variability of requirements in this age range is complicated because of the physiological changes that occur. In this report, median requirements for absorbed iron are estimated for each year of age, but the variability of requirement and the requirement for absorbed iron at the ninety seven and one-half percentile are estimated at the midpoint for children 9 through 13 years (11 years) and adolescents 14 through 18 years (16 years).
For modeling, the entire age range is treated as a continuum; for