For example, the median daily need for nonstorage iron for a 16-year-old boy is 0.001 mg/day (2.75 × 0.13 ÷ 365) after rounding. No provision is made for iron storage after the age of 9 years. It is not a component of requirement though it can be expected to occur when intake exceeds actual requirement.
Menstrual Losses. Iron losses in the menses can be calculated when the average blood loss, the average hemoglobin concentration, and concentration of iron in hemoglobin (3.39 mg/g) (Smith and Rios, 1974) are known. It was deemed appropriate to use the blood losses reported by Hallberg and coworkers (1966a, 1966b) with additional information from Hallberg and Rossander-Hulthen (1991) and, more specifically, to use the blood loss estimates for 15-year-old girls. These losses were lower than those reported for older ages.
Several important features of these and other data related to menstrual blood loss were recognized in developing models to predict requirements:
Menstrual losses are highly variable among women and the distribution of losses in the population shows major skewing, with some women having losses in excess of three times the median value.
Menstrual losses are very consistent from one menstrual cycle to the next for an individual woman.
Once the woman’s menstrual pattern is established after her menarche, menstrual losses are essentially unchanged until the onset of menopause in healthy women. Hallberg and coworkers (1966b) found very little difference in blood loss with age. Losses were lower in the 15-year-old group, but incomplete collection might have been a factor. Cole and coworkers (1971) reported a small effect of age that was attributed to two covariates, parity and infant birth weight.
Contraceptive methods have a major impact on menstrual losses. Bleeding is significantly increased by the use of certain intrauterine devices and significantly decreased in individuals taking oral contraceptives.
Age, body size, and parity were not considered to have an effect of sufficient magnitude on menstrual blood losses to include them as factors in the models for estimating iron requirements in females—except with regard to the lower menstrual loss assumed for adolescents.
The data on menstrual losses reported by Hallberg and coworkers