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Background: A new index to determine body iron promises a simpler approach to monitoring iron deficiency (ID) prevalence., Objective: Our objective was to compare ID defined as body iron <0 mg/kg and calculated from the log ratio of transferrin receptor to ferritin (the body iron model) to ID defined as >/=2 of 3 abnormal concentrations in ferritin, transferrin saturation, or erythrocyte protoporphyrin (the ferritin model)., Design: We used measures of iron status and inflammation from 486 children aged 1-2 y, 848 children aged 3-5 y, and 3742 nonpregnant females aged 12-49 y from the National Health and Nutrition Examination Survey 2003-2006., Results: ID prevalences (+/-SE) based on the body iron model in children (1-2 and 3-5 y) and in females (12-19 and 20-49 y) were 14.4 +/- 1.9%, 3.7 +/- 0.8%, 9.3 +/- 1.0%, and 9.2 +/- 1.6%, respectively. ID prevalences based on the ferritin model in children (3-5 y) and females (12-19 and 20-49 y) were 4.5 +/- 0.9%, 15.6 +/- 1.2%, and 15.7 +/- 0.8%, respectively. The kappa statistics for agreement between the 2 models were 0.5-0.7. Among females (12-49 y) the positive predictive values of ID based on the body iron model and the ferritin model for identifying anemia were 43 +/- 3% and 30 +/- 2%, respectively, whereas negative predictive values did not differ. C-reactive protein was elevated in 28.8 +/- 3.1% of females with ID by the ferritin model but not by the body iron model and in 0% of persons with ID by the body iron model but not by the ferritin model., Conclusions: The agreement between the 2 indexes was fair to good. Among females, the body iron model produced lower estimates of ID prevalence, better predicted anemia, and appeared to be less affected by inflammation than the ferritin model.

Iron deficiency severe enough to cause anemia is associated with significant morbidity while uncontrolled iron absorption which occurs in disorders such as hereditary hemochromatosis causes multiorgan failure and early death. Preliminary data from the Third National Health and Nutrition Examination Survey demonstrate that the prevalence of iron deficiency anemia in the United States is now very low. This implies that the current iron consumption is adequate for most individuals. An important unresolved question relates to the necessity for further reducing the prevalence of iron deficiency without anemia. More information is required to determine whether this lesser degree of iron deficiency is harmful. Recent survey data indicate that concomitantly with the reduced prevalence of iron deficiency there has been a rise in serum ferritin concentrations in American men and postmenopausal women. These findings have led to concern about the effectiveness of the physiological mechanisms for limiting storage accumulation in normal individuals and carriers of the hemochromatosis gene when dietary iron content is high. Furthermore, recent epidemiological observations suggest that a modest increase in iron stores (in a range previously considered safe) is a possible risk factor for ischemic heart disease and cancer; however, a causal relationship remains to be proven. Nonetheless, because there is no known benefit of high iron storage status, it seems prudent to avoid further increases in and possibly to reduce the dietary iron intake of men and postmenopausal women. Mean intake in these groups exceeds the current RDA by a significant margin. Therefore, the sources of dietary iron as well as other factors contributing to high serum ferritin values have to be defined. Also, efforts should be made to increase the awareness of professionals and the public about the possible risks of excessive dietary iron. The complexity of the Western diet and an incomplete understanding of all of the factors affecting serum ferritin concentrations make it very difficult to specify a safe upper range for daily iron intake at the present time.

Clinical manifestations attributable to the damaging effects of iron occur when the total body iron is 5-10 times higher than normal. In adults this degree of iron overload occurs in hereditary hemochromatosis, a human leukocyte antigen (HLA)-linked autosomal recessive disorder, as well as in secondary iron-overload conditions.

Traditionally the iron status of a population is assessed by estimating the prevalence of iron deficiency anemia. This approach is inadequate in countries where the diet is heavily fortified with iron because it conveys no information about the iron-replete segment of the population. In the present study iron status of a US adult population was evaluated using data collected in the second National Health and Nutrition Examination Survey (NHANES II). Body iron was estimated in each of 2,829 individuals from measurements of hemoglobin concentration, serum ferritin, transferrin saturation, and erythrocyte protoporphyrin. When individuals between 18 and 64 years of age were divided on the basis of sex and menstrual status, body iron reserves were normally distributed and averaged 309 mg in women 18 to 44 years, 608 mg in women 45 to 64 years, and 776 mg in men 18 to 64 years. The dispersion of storage iron in these groups was similar, with standard deviations of 346, 372, and 313 mg, respectively. The prevalence of iron deficiency anemia was surprisingly low, ranging from only 0.2% in adult men to 2.6% and 1.9% in pre- and postmenopausal women, respectively. Epidemiologic methods that examine iron status in the entire population assume importance in light of evidence that in certain segments of the US population, iron deficiency anemia is now less common than the homozygous state for hereditary hemochromatosis.

Studies of iron nutriture in the elderly are limited and very few include observations on individuals over the age of 75. The two Health and Nutrition Examination Surveys carried out by the United States Department of Health, Education and Welfare demonstrate that the mean iron intake of Americans is adequate until the age of 75. However, with changes in the major food sources there is a decrease in iron derived from meat and a concomitant rise in the proportion supplied by breakfast cereals. Alterations in dietary iron bioavailability++ that may result from this have not been studied. Physiological data suggest that the elderly do not represent a target population for iron deficiency since iron requirements are no greater than those of adult men and lower than those of children and menstruating women. Furthermore, there is little direct evidence of a high prevalence of iron deficiency in the elderly, but the laboratory measurements that have proved useful in defining iron status in younger people have not been standardized for or extensively used in older people. Anemia is still the most important known consequence of significant iron deficiency. However, the application of Hb or hematocrit standards used in younger people to the elderly as well as the assumption that anemia can be equated with iron deficiency invalidates the conclusions of many surveys. Hb and hematocrit measurements are not suitable screening tests for iron deficiency in the elderly and there is an urgent need for a clearer understanding of the physiological and nutritional factors responsible for lower Hb values in older people, particularly older Blacks.