Recommended Nutrient Intakes for Iron

Recommended intakes of dietary iron are based on the requirement for absorbed iron and assumptions about the bioavailability of iron in the diet. They are meant to cover the iron needs of nearly the entire population group. Thus, the amount of dietary iron necessary to meet an iron requirement depends in large part on the bioavailability of iron in the diet (Figure 3). Americans consume approximately 15 mg of iron daily from a diet that is considered moderately to highly bioavailable (10-15%) due to the meat and ascorbic acid content. Studies in European countries suggest that iron intake

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Figure 3 The Recommended Nutrient Intake (RNI) for iron given different levels of bioavailability of iron in the diet: 5%, low; 10%, moderate; and 15%, high. The RNI is based on the amount of iron necessary to meet requirements of 95% of the population for each age/sex group. Because typical iron intakes range from 10 to 15mg/day, iron requirements are nearly impossible to meet on low-bioavailability diets. (Data from the Food and Agriculture Organization of the United Nations (2001) Iron. In Human Vitamin and Mineral Requirements: Report of a Joint FAO/WHO Expert Consultation, Bangkok, Thailand, pp. 195-221. Rome: FAO.)

averages 10mg/day, representing a decline in dietary iron. Although estimates of total iron intake in developing countries are not substantially lower than that, iron is often consumed in plant-based diets that inhibit its absorption and contain few animal products to counterbalance that effect, such that the bioavailability of iron is closer to 5%. Thus, Figure 3 demonstrates the total amount of dietary iron that would be necessary to meet the iron requirements of various population groups based on its bioavailability. Where intakes are sufficient and bioavailability adequate, dietary iron can meet the iron needs of adolescent boys and adult men and also lactating and postmenopausal women. However, regardless of bioavailability, iron requirements are not met by many adolescent girls and adult menstruating women who have above average menstrual blood loss. Few if any population groups can achieve iron intakes sufficient to meet iron requirements when bioavailability of iron is poor.

Dietary recommendations for infants are based on the iron content and bioavailability of human milk. The iron in infant formula is much less bioavailable (10%) than that of human milk and is thus present in greater concentrations than that of human milk. Infants who are not breast-fed should consume iron-fortified formula. Complementary foods offered after 6 months of age can potentially meet iron needs if they have a high content of meat and ascorbic acid. This is rarely the case in developing or developed countries, and fortified infant cereals and iron drops are often introduced at this time in developed countries. In developing countries where diets are poor in bioavailable iron, iron-fortified weaning foods are not commonly consumed, and iron supplements are rarely given to infants and children.

Pregnant women rarely have sufficient iron stores and consume diets adequate to maintain positive iron balance, particularly in the latter half of pregnancy, as previously discussed. They cannot meet their iron requirements through diet alone even in developed countries, where high iron content diets with high bioavailability are common. Supplementation is universally recommended for pregnant women, as discussed later.

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Responses

  • melissa
    Why iron requirment high in adolcence boys?
    3 years ago

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