Dietary Reference Intakes The Essential Guide to Nutrient Requirements (2006) / Chapter Skim
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Pages 328-339
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From page 328... ...
TABLE 1 Dietary Reference Intakes for Iron by Life Stage Group DRI values (mg/day) EARa RDAb AIc ULd males females males females Life stage group 0 through 6 mo 0.27 40 7 through 12 mo 6.9 6.9 11 11 40 1 through 3 y 3.0 3.0 7 7 40 4 through 8 y 4.1 4.1 10 10 40 9 through 13 y 5.9 5.7 8 8 40 14 through 18 y 7.7 7.9 11 15 45 19 through 30 y 6.0 8.1 8 18 45 31 through 50 y 6.0 8.1 8 18 45 51 through 70 y 6.0 5.0 8 8 45 > 70 y 6.0 5.0 8 8 45 Pregnancy £ 18 y 23 27 45 19 through 50 y 22 27 45 Lactation £ 18 y 7 10 45 19 through 50 y 6.5 9 45 a EAR = Estimated Average Requirement.
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From page 329... ...
PART III: IRON 329 IRON I ron is a critical component of several proteins, including enzymes, cyto chromes, myoglobin, and hemoglobin, the latter of which transports oxy gen throughout the body. Almost two-thirds of the body's iron is found in hemoglobin that is present in circulating erythrocytes and involved in the transport of oxygen from the environment to tissues throughout the body for metabolism.
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From page 330... ...
DRIs: THE ESSENTIAL GUIDE TO NUTRIENT REQUIREMENTS 330 iron-sulfur enzymes (flavoproteins, hemeflavoproteins) , proteins for iron stor age and transport (transferrin, lactoferrin, ferritin)
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From page 331... ...
PART III: IRON 331 DETERMINING REQUIREMENTS Determining Requirements The requirements for iron are based on factorial modeling using the following factors: basal iron losses; menstrual losses; fetal requirements in pregnancy; increased requirements during growth for the expansion of blood volume; and increased tissue and storage iron. It is important to note that iron requirements are known to be skewed rather than normally distributed for menstruating women.
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From page 332... ...
DRIs: THE ESSENTIAL GUIDE TO NUTRIENT REQUIREMENTS 332 who are on HRT may have higher iron requirements than postmenopausal women who are not. Vegetarian diets: Because heme iron is more bioavailable than nonheme iron (milk products and eggs are of animal origin, but they contain only nonheme iron)
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From page 333... ...
PART III: IRON 333 The UL The Tolerable Upper Intake Level (UL) is the highest level of daily nutrient intake that is likely to pose no risk of adverse effects for almost all healthy people.
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From page 334... ...
DRIs: THE ESSENTIAL GUIDE TO NUTRIENT REQUIREMENTS 334 Dietary Supplements The 1986 National Health Interview Survey (NHIS) reported that approximately 21–25 percent of women and 16 percent of men consumed a supplement con taining iron.
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From page 335... ...
PART III: IRON 335 TABLE 2 Continued Substance Potential Interaction Notes Animal Meat, fish, and poultry The mechanism of this enhancing effect is poorly muscle improve nonheme iron studied, but is likely to involve low molecular weight tissue absorption. peptides that are released during digestion.
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From page 336... ...
DRIs: THE ESSENTIAL GUIDE TO NUTRIENT REQUIREMENTS 336 INADEQUATE INTAKE AND DEFICIENCY Iron deficiency anemia is the most common nutritional deficiency in the world. The most important functional indicators of iron deficiency are reduced physi cal work capacity, delayed psychomotor development in infants, impaired cog nitive function, and adverse effects for both the mother and the fetus (such as maternal anemia, premature delivery, low birth weight, and increased perinatal infant mortality)
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From page 337... ...
PART III: IRON 337 EXCESS INTAKE The risk of adverse effects of excessive iron intake from dietary sources appears to be low in the general population. Adverse effects may include the following: • Acute toxicity with vomiting and diarrhea, followed by cardiovascular, central nervous system, kidney, liver, and hematological effects.
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From page 338... ...
DRIs: THE ESSENTIAL GUIDE TO NUTRIENT REQUIREMENTS 338 KEY POINTS FOR IRON Iron is a critical component of several proteins, including 3 cytochromes, myoglobin, and hemoglobin, the latter of which transports oxygen throughout the body. The requirements for iron are based on factorial modeling using 3 the following factors: basal iron losses; menstrual losses; fetal requirements in pregnancy; increased requirement during growth for the expansion of blood volume; and increased tissue and storage iron.
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From page 339... ...
PART III: IRON 339 Three levels of iron deficiency are customarily identified: 3 depleted iron stores, early functional iron deficiency, and iron deficiency anemia. Adverse effects associated with excessive iron intake include 3 acute toxicity, gastrointestinal distress, and secondary iron overload.
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