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Estimation of the Variability of Requirements. The variability of requirement was based on basal needs modeled as described for nonpregnant, nonlactating women and milk secretion modeled from the above distribution. Large breast-feeding studies suggest CVs between 10 and 40 percent (Dewey and Lonnerdal, 1983; Vaughan et al., 1979). A CV of 30 percent was adopted and iron concentration of mature human milk, for the purpose of modeling, is taken as 0.35 mg/L assuming normality with a CV of 33 percent.

Iron EAR and RDA Summary, Lactation

EAR for Lactation

14–18 years

7 mg/day of iron

19–30 years

6.5 mg/day of iron

31–50 years

6.5 mg/day of iron

The RDA for iron is set by determining the estimate of requirements at the ninety-seven and one-half percentile.

RDA for Lactation

14–18 years

10 mg/day of iron

19–30 years

9 mg/day of iron

31–50 years

9 mg/day of iron

Special Considerations

Use of Oral Contraceptives and Hormone Replacement Therapy

It has been reported that approximately 17 percent of women in the United States use oral contraceptives (Abma et al., 1997), which are known to reduce menstrual blood loss. Although many studies have documented lower menstrual blood losses among women using oral contraceptives, only one study actually allowed estimation of the magnitude of reduction, compared to expected loss. A reanalysis of data from that study (Nilsson and Solvell, 1967) suggested that a reasonable estimate of effect would be the equivalent of a 60 percent reduction from expected loss. Therefore, the requirement at the fiftieth and ninety-seven and one-half percentile for adolescent girls taking oral contraceptives is 6.9 and 11.4 mg/day, respectively and 6.4 and 10.9 mg/day for premenopausal women (see Appendix Table I-4).

Hormone replacement therapy (HRT), which provides estrogen and progesterone, is commonly practiced by postmenopausal



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