the average requirement of iron for children over the age of 1 year, adolescents, and nonpregnant adults consuming the mixed diet typically consumed in the United States and Canada. The diets of most infants aged 7 through 12 months contain little meat and are rich in cereals and vegetables, a diet that approximates a medium bioavailability of 10 percent (Davidsson et al., 1997; Fairweather-Tait et al., 1995a; FAO/WHO, 1988; Skinner et al., 1997).

No functional criteria of iron status have been demonstrated that reflect response to dietary intake in young infants. Thus, recommended intakes of iron are based on an Adequate Intake (AI) that reflects the observed mean iron intake of infants principally fed human milk.

At birth, the normal full-term infant has a considerable endowment of iron and a very high hemoglobin concentration. Because the mobilization of body iron stores is very high, the requirement for exogenous iron is virtually zero. After birth, an active process of shifts in iron compartments takes place. Fetal hemoglobin concentration falls, usually reaching a nadir when the infant is between 4 and 6 months of age, and adult hemoglobin formation begins because hematopoiesis is very active. Some time between 4 and 6 months, exogenous sources of iron are used and after 6 months, it can be assumed that the stores endowed at birth have been utilized and that the physiological norm is to meet iron needs from exogenous rather than endogenous sources as erythropoiesis becomes more active. Thereafter, the hemoglobin concentration rises slowly but continuously (1 to 2 g/L/year) through at least puberty (longer in males) (Beaton et al., 1989). This normal physiological sequence of events complicates the estimation of iron requirements.

It is widely accepted that the iron intake of infants exclusively fed human milk must meet or exceed the actual needs of almost all of these infants and that the described pattern of utilization of iron stores is physiologically normal, not indicative of the beginning of iron deficiency. For this age group, it is assumed that the iron provided by human milk is adequate to meet the iron needs of the infant exclusively fed human milk from birth through 6 months. Therefore, the method described in Chapter 2 is used to set an AI

Front Matter (R1-R24)

Summary (1-28)

1 Introduction to Dietary Reference Intakes (29-43)

2 Overview and Methods (44-59)

3 A Model for the Development of Tolerable Upper Intake Levels (60-81)

4 Vitamin A (82-161)

5 Vitamin K (162-196)

6 Chromium (197-223)

7 Copper (224-257)

8 Iodine (258-289)

9 Iron (290-393)

10 Manganese (394-419)

11 Molybdenum (420-441)

12 Zinc (442-501)

13 Arsenic, Boron, Nickel, Silicon, and Vanadium (502-553)

14 Uses of Dietary Reference Intakes (554-579)

15 A Research Agenda (580-586)

Appendix A Origin and Framework of the Development of Dietary Reference Intake (587-590)

Appendix B Acknowledgments (591-593)

Appendix C Dietary Intake Data from the Third National Health and Nutrition Examination Survey (NHANES III), 1988-1994 (594-643)

Appendix D Dietary Intake Data from the Continuing Survey of Food Intakes by Individuals (CSFII), 1994-1996 (644-653)

Appendix E Dietary Intake Data from the U.S. Food and Drug Administration Total Diet Study, 1991-1997 (654-673)

Appendix F Canadian Dietary Intake Data, 1990 (674-679)

Appendix G Biochemical Indicators for Iron, Vitamin A, and Iodine from the Third National Health and Nutrition Examination Survey (NHANES III), 1988-1994 (680-691)

Appendix H Comparison of Vitamin A and Iron Intake and Biochemical Indicators from the Third National Health and Nutrition Examination Survey (NHANES III), 1988-1994 (692-696)

Appendix I Iron Intakes and Estimated Percentile of the Distribution of Iron Requirements from the Continuing Survey of Food Intakes by Individuals (CSFII), 1994-1996 (697-703)

Appendix J Glossary and Acronyms (704-708)

Appendix K Conversion of Units (709-709)

Appendix L Options for Dealing with Uncertainties (710-714)

Appendix M Biographical Sketches of Panel and Subcommittee Members (715-728)

Index (729-769)

Summary Table, Dietary Reference Intakes: Recommended Intakes for Individuals, Vitamins (770-771)

Summary Table, Dietary Reference Intakes: Recommended Intakes for Individuals, Elements (772-773)